Chemical Modeling for Predicting the Abundances of Certain Aldimines and Amines in Hot Cores

Milan Sil; Prasanta Gorai; Ankan Das; Bratati Bhat; Emmanuel E. Etim; Sandip K. Chakrabarti

doi:10.3847/1538-4357/aa984d

1. Introduction

Almost 200 species have been discovered in the interstellar medium (ISM) or circumstellar shells, and most of them are organic in nature (https://www.astro.uni-koeln.de/cdms/molecules). The presence of numerous complex organic molecules in the ISM has been reported earlier (Cronin & Chang 1993; Herbst 2006). The chemical richness of extraterrestrial media points to the formation of biomolecules in the ISM. There are some studies on the formation of complex prebiotic molecules in collapsing clouds and star-forming regions (Chakrabarti & Chakrabarti 2000a, 2000b; Garrod 2013; Chakrabarti et al. 2015). It is suggested that if the abundance of biomolecules is too small for detection, their precursors may be observed for estimating the abundances of these biomolecules (Majumdar et al. 2012, 2013). Aldimines and amines are the building blocks of amino acids (Godfrey et al. 1973; Holtom et al. 2005). Thus, the discovery of these species under astrophysical circumstances could be treated as important clues leading to the origin of life.

Aldimines are very important, as they are seen within the reactions of Strecker-type synthesis. The Strecker synthesis prepares α-aminonitriles, which are versatile intermediates for the synthesis of amino acids via hydrolysis of nitriles. However, a Strecker-type formation route was found to be less important (Elsila et al. 2007). Therefore, we investigate a total of 34 molecules from six isomeric groups, namely, ${\mathrm{CH}}_{3}{\rm{N}}$ , ${\mathrm{CH}}_{5}{\rm{N}}$ , ${{\rm{C}}}_{2}{{\rm{H}}}_{5}{\rm{N}}$ , ${{\rm{C}}}_{2}{{\rm{H}}}_{7}{\rm{N}},{{\rm{C}}}_{3}{{\rm{H}}}_{7}{\rm{N}}$ , and ${{\rm{C}}}_{3}{{\rm{H}}}_{9}{\rm{N}}$ , to find out the possibility of detecting some of the aldimines and amines, which are the precursor of amino acids. From these six isomeric groups, at least one species was observed from each of the ${\mathrm{CH}}_{3}{\rm{N}},{\mathrm{CH}}_{5}{\rm{N}}$ , and ${{\rm{C}}}_{2}{{\rm{H}}}_{5}{\rm{N}}$ isomeric groups. However, to date, any species from the ${{\rm{C}}}_{2}{{\rm{H}}}_{7}{\rm{N}},{{\rm{C}}}_{3}{{\rm{H}}}_{7}{\rm{N}}$ , and ${{\rm{C}}}_{3}{{\rm{H}}}_{9}{\rm{N}}$ isomeric groups have yet to be detected.

From the ${\mathrm{CH}}_{3}{\rm{N}}$ isomeric group, methanimine ( ${\mathrm{CH}}_{2}\mathrm{NH}$ ) was observed in Sgr B2 (Godfrey et al. 1973). The simplest amino acid, namely, glycine, could have been formed by the reaction between methanimine and formic acid (Godfrey et al. 1973). In that sense, methanimine is the precursor molecule for glycine (Suzuki et al. 2016). Similarly, from the ${\mathrm{CH}}_{5}{\rm{N}}$ isomeric group, methylamine ( ${\mathrm{CH}}_{3}{\mathrm{NH}}_{2}$ ) was detected (Fourikis et al. 1974; Kaifu et al. 1974) in both Sgr B2 and Orion A. Holtom et al. (2005) showed from theoretical and experimental studies that glycine could have been formed by the reaction with another precursor molecule (reaction between methylamine and ${\mathrm{CO}}_{2}$ under UV irradiation on an icy grain mantle). On the other hand, methylamine could be produced by two successive hydrogen addition reactions with methanimine. It can also be formed by four successive hydrogen additions to HCN on the surface of grains (Godfrey et al. 1973; Woon 2002; Theule et al. 2011). Both the precursor molecules (methylamine and ethylamine) of glycine were observed in comet Wild 2 (Glavin et al. 2008) and in the coma of 67P/Churyumov–Gerasimenko (by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis mass spectrometer; Altwegg et al. 2016).

Microwave and millimeter-wave spectra of the two conformers of ethanimine (E- and Z-ethanimine) were characterized in order to guide the astronomical searches (Brown et al. 1980; Lovas et al. 1980). They recommended that ethanimine from the ${{\rm{C}}}_{2}{{\rm{H}}}_{5}{\rm{N}}$ isomeric group should be a possible interstellar molecule that can be seen in space. Finally, ethanimine has been detected with both forms in the same sources where methanimine has already been observed (Loomis et al. 2013).

From the ${{\rm{C}}}_{2}{{\rm{H}}}_{7}{\rm{N}},{{\rm{C}}}_{3}{{\rm{H}}}_{7}{\rm{N}}$ , and ${{\rm{C}}}_{3}{{\rm{H}}}_{9}{\rm{N}}$ isomeric groups, ethylamine, propanimine, and trimethylamine are of special interest because they could possibly play a role in the formation of amino acids and other prebiotic molecules. Recently, Margulès et al. (2015) have performed the first spectroscopic study of the propanimine molecule. Similar to the ethanimine molecule, Margulès et al. (2015) found that propanimine can exist in two conformations, E-propanimine and Z-propanimine. In order to detect these species under astrophysical conditions, it is essential to know the spectroscopic details and the chemical abundances of these species.

Section 2 describes the computational details and methodology of our work. Results are extensively discussed in Section 3. General conclusions of this work are provided in Section 4. In the Appendix, we present the gas phase formation and destruction pathways. As the supplementary materials of this work, we provide the catalog files for ethylamine and (1Z)-1-propanimine, which could be very useful for the future detection of these species in the ISM.

2. Computational Details and Methodology

2.1. Quantum Chemical Calculations

All the calculations are performed with the Gaussian 09 suite of programs (Frisch et al. 2013). Table 1 shows some ice phase reactions that lead to the formation of various interstellar amines and aldimines. Some of these reactions are radical–radical (RR) in nature and thus can happen at each encounter. However, there are some reactions between neutrals and radicals (NR) that often possess activation barriers. The QST2 method with B3LYP/6-311++G(d,p) levels of theory is employed to calculate various energy barriers (activation barrier and Gibbs free energy of activation). Moreover, the QST2 method is also used to determine reaction pathways and transition state structures.

Table 1. Ice Phase Formation Pathways

Reaction Number (Type)	Reaction	Activation Barrier (K)
R1(RR)^a	${\rm{N}}+{\mathrm{CH}}_{3}\to {\mathrm{CH}}_{2\mathrm{NH}}$	0.0
R2(RR)^a	$\mathrm{NH}+{\mathrm{CH}}_{2}\to {\mathrm{CH}}_{2}\mathrm{NH}$	0.0
R3(RR)^a	${\mathrm{NH}}_{2}+\mathrm{CH}\to {\mathrm{CH}}_{2}\mathrm{NH}$	0.0
R4(NR)^a	$\mathrm{HCN}+{\rm{H}}\to {{\rm{H}}}_{2}\mathrm{CN}$	3647^b
R5(NR)^a	$\mathrm{HCN}+{\rm{H}}\to \mathrm{HCNH}$	6440^b
R6(RR)^a	${{\rm{H}}}_{2}\mathrm{CN}+{\rm{H}}\to {\mathrm{CH}}_{2}\mathrm{NH}$	0.0
R7(RR)^a	$\mathrm{HCNH}+{\rm{H}}\to {\mathrm{CH}}_{2}\mathrm{NH}$	0.0
R8(NR)^a	${\mathrm{CH}}_{2}\mathrm{NH}+{\rm{H}}\to {\mathrm{CH}}_{3}\mathrm{NH}$	2134^b
R9(NR)^a	${\mathrm{CH}}_{2}\mathrm{NH}+{\rm{H}}\to {\mathrm{CH}}_{2}{\mathrm{NH}}_{2}$	3170^b
R10(RR)^a	${\mathrm{CH}}_{3}\mathrm{NH}+{\rm{H}}\to {\mathrm{CH}}_{3}{\mathrm{NH}}_{2}$	0.0
R11(RR)^a	${\mathrm{CH}}_{2}{\mathrm{NH}}_{2}+{\rm{H}}\to {\mathrm{CH}}_{3}{\mathrm{NH}}_{2}$	0.0
R12(RR)^c	${\mathrm{CH}}_{2}\mathrm{CN}+{\rm{H}}\to {\mathrm{CH}}_{3}\mathrm{CN}$	0.0
R13(RR)^d	${\mathrm{CH}}_{3}+\mathrm{CN}\to {\mathrm{CH}}_{3}\mathrm{CN}$	0.0
R14(NR)^e	${\mathrm{CH}}_{3}\mathrm{CN}+{\rm{H}}\to {\mathrm{CH}}_{3}\mathrm{CNH}$	1400^b
R15(RR)^e	${\mathrm{CH}}_{3}\mathrm{CNH}+{\rm{H}}\to {\mathrm{CH}}_{3}\mathrm{CHNH}$	0.0
R16(RR)^e	${\mathrm{CH}}_{3}+{{\rm{H}}}_{2}\mathrm{CN}\to {\mathrm{CH}}_{3}\mathrm{CHNH}$	0.0
R17(NR)	${\mathrm{CH}}_{3}\mathrm{CHNH}+{\rm{H}}\to {\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{NH}$	1846
R18(RR)	${\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{NH}+{\rm{H}}\to {\mathrm{CH}}_{3}{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}$	0.0
R19(RR)	${{\rm{C}}}_{2}{{\rm{H}}}_{5}+{{\rm{H}}}_{2}\mathrm{CN}\to {\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CHNH}$	0.0
R20(RR)	${{\rm{C}}}_{2}{{\rm{H}}}_{5}+\mathrm{CN}\to {\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CN}$	0.0
R21(NR)	${\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CN}+{\rm{H}}\to {\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CNH}$	2712
R22(RR)	${\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CNH}+{\rm{H}}\to {\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CHNH}$	0.0

Notes.

^aSuzuki et al. (2016). ^bWoon (2002). ^cHasegawa et al. (1992). ^dQuan et al. (2010). ^eQuan et al. (2016).

Download table as: ASCII Typeset image

In order to estimate accurate enthalpies of formation of all the species of various isomeric groups, the Gaussian G4 composite method is used. In arriving at an accurate total energy for a given species, the G4 composite method performs a sequence of well-defined ab initio molecular calculations (Curtiss et al. 2007; Etim et al. 2016). Each fully optimized structure is verified to be a stationary point (having non-negative frequency) by harmonic vibrational frequency calculations. For computing the enthalpy of formation, we calculate atomization energy of molecules. Experimental values of the enthalpy of formation of atoms are taken from Curtiss et al. (1997). In Table 2 we summarize the present astronomical status and enthalpy of formation ( ${{\rm{\Delta }}}_{f}{H}^{O}$ ) of all the species considered here. Subsequently, in all the tables we arrange the species according to the ascending order of the enthalpy of formation. Some experimental values of the enthalpy of formation (if available) are also shown for comparison. Relative energies of each isomeric group member are also shown with the G4 level of theory. Osmont et al. (2007) found that this level of theory is also suitable for the computation of the enthalpies of formation. Moreover, in Table 2 we also include our calculated enthalpies of formation with the B3LYP/6-31G(d,p) level of theory. In our case, we found that the calculated enthalpies of formation with the B3LYP/6-31G(d,p) level of theory are closer to the experimentally obtained values than those of the G4 composite method.

Table 2. Enthalpy of Formation and Electronic Energy (E0) with Zero-point Energy (ZPE) and Relative Energy with the G4 Composite Method for All Species of Six Isomeric Groups

Number	Species	Astronomical Status	E0+ZPE	Calculated ${{\rm{\Delta }}}_{f}{H}^{0}$	Experimental ${{\rm{\Delta }}}_{f}{H}^{0}$
			in Hartree/Particle	Using G4 Composite Method	(in Kcal/mol)
			(Relative Energy	(Using B3LYP/6-31G(d,p) Method)
			in Kcal/mol)	(in Kcal/mol)
${\mathrm{CH}}_{3}{\rm{N}}$ Isomeric Group

1	Methanimine	observed^a	−94.596377 (0.00)	18.2604366 (20.0748878)	⋯
2	${\lambda }^{1}$ -Azanylmethane	not observed	−94.519754 (48.08)	66.3715977 (66.9874996)	⋯

${\mathrm{CH}}_{5}{\rm{N}}$ Isomeric Group

1	Methylamine	observed^b^,^c	−95.802182 (0.00)	−9.00194363 (−7.3082602)	−5.37763^d

${{\rm{C}}}_{2}{{\rm{H}}}_{5}{\rm{N}}$ Isomeric Group

1	E-Ethanimine	observed^e	−133.896198 (0.00)	5.90189865 (7.9892830)	5.74^f
2	Z-Ethanimine	observed^e	−133.895732 (0.29)	6.20797719 (8.3293932)	⋯
3	Ethenamine	not observed	−133.889919 (3.94)	9.8284533(12.7953785)	⋯
4	N-Methylmethanimine	not observed	−133.884403 (7.40)	13.275162 (15.5507728)	10.51625^f
5	Aziridine	not observed	−133.862508 (21.14)	26.62315 (29.3566098)	30.11472^d

${{\rm{C}}}_{2}{{\rm{H}}}_{7}{\rm{N}}$ Isomeric Group

1	Ethylamine (trans)	not observed	−135.094044 (0.00)	−16.366079 (−14.5306661)	⋯
2	Ethylamine (gauche)	not observed	−135.09341 (0.40)	−15.955933 (−14.1008221)	−11.3528^d
3	Dimethylamine	not observed	−135.084612 (5.92)	−10.437412 (−8.4344111)	−4.445507^d

${{\rm{C}}}_{3}{{\rm{H}}}_{7}{\rm{N}}$ Isomeric Group

1	2-Propanimine	not observed	−173.193699 (0.00)	−4.7991787 (−2.2671314)	⋯
2	2-Propenamine	not observed	−173.18563 (5.06)	0.18444024 (3.5818848)	⋯
3	(1E)-1-Propanimine	not observed	−173.183877 (6.163)	1.287921 (3.7186819)	⋯
4	(1Z)-1-Propen-1-amine	not observed	−173.183875 (6.164)	1.2981179 (3.7205644)	⋯
5	(1E)-N-Methylethanimine	not observed	−173.183821 (6.20)	1.4335242 (4.0067087)	⋯
6	(1Z)-1-Propanimine	not observed	−173.183423 (6.45)	1.59211071 (4.0393392)	⋯
7	(1E)-1-Propen-1-amine	not observed	−173.181835 (7.44)	2.6644726 (5.9243778)	⋯
8	N-Ethylmethanimine	not observed	−173.17536 (11.51)	6.5932994 (12.4893824)	⋯
9	N-Methylethenamine	not observed	−173.171735 (13.78)	9.0000089 (12.4893824)	⋯
10	Allylamine	not observed	−173.168277 (15.95)	11.096984 (14.2338589)	⋯
11	Cyclopropanamine	not observed	−173.159802 (21.27)	15.985053 (18.7632226)	18.475^d
12	S-2-Methylaziridine	not observed	−173.157389 (22.7846)	17.531164 (20.4380455)	⋯
13	(2S)-2-Methylaziridine	not observed	−173.157388 (22.7853)	17.535559 (20.4405556)	⋯
14	2-Methylaziridine (trans)	not observed	−173.157386 (22.7865)	17.543877 (20.4393006)	⋯
15	2-Methylaziridine (cis)	not observed	−173.156991 (23.03)	17.7562713 (20.7574479)	⋯
16	Azetidine	not observed	−173.1536 (25.16)	19.607872 (22.3205741)	⋯
17	Methylaziridine	not observed	−173.147784 (28.81)	23.520139 (26.5719511)	⋯
18	N-Methylethanamine	not observed	−173.126259 (42.32)	37.837958 (41.5192279)	⋯
19	(Dimethyliminio)methanide	not observed	−173.112784 (50.77)	45.881231 (50.7837785)	⋯

${{\rm{C}}}_{3}{{\rm{H}}}_{9}{\rm{N}}$ Isomeric Group

1	2-Aminopropane	not observed	−174.385779 (0.00)	−23.5149351 (−21.4656727)	−20.0048^d
2	Propylamine	not observed	−174.381773 (2.51)	−20.9566988 (−18.7880896)	−16.7543^d
3	Ethylmethylamine	not observed	−174.375953 (6.16)	−17.3159833 (−15.0857834)	⋯
4	Trimethylamine	not observed	−174.369667 (10.11)	−13.4808824 (−10.9573983)	−5.64054^d

Notes. Additional computation of enthalpy of formation by the B3LYP/6-31G(d,p) level of theory is pointed out in parentheses.

^aGodfrey et al. (1973). ^bKaifu et al. (1974). ^cFourikis et al. (1974). ^dFrenkel et al. (1994). ^eLoomis et al. (2013). ^fNIST Chemistry Webbook (http://webbook.nist.gov/chemistry).

Download table as: ASCII Typeset image

Species with permanent electric dipole moments are generally detected from their rotational transitions, and about 80% of all known interstellar and circumstellar molecules were discovered by these transitions. Intensity of any rotational transition is especially dependent on the temperature and the components (a-type, b-type, and c-type) of the dipole moment (Fortman et al. 2014; McMillan et al. 2014). Relative signs of the dipole moment components may cause the change of intensities of some transitions (Müller et al. 2016). These intensities are directly proportional to the square of the dipole moment and inversely proportional to the rotational partition function. Thus, in general, for a fixed temperature, the higher the dipole moments, the higher the intensities. All the molecules considered here have a nonzero permanent electric dipole moment. Dipole moment components along the inertial axis ( ${\mu }_{a},{\mu }_{b}$ , and ${\mu }_{c}$ ) are summarized in Table 3. For the computation of the dipole moment components, we use various levels of theory. Among them, our calculations at the HF level yielded excellent agreement with the existing experimental results. Lakard (2003) already analyzed permanent electric dipole moments of some aliphatic primary amines. They used various models for comparing their calculated results with the experimentally obtained results. They found that the HF/6-31G(3df) model is more reliable for the aliphatic amines. According to their calculations, on an average, this model can predict values of permanent electric dipole moments with a deviation of only 2.1% of its experimental values. With reference to their results, here we use the same method and the basis set to compute the dipole moment components. In Table 3 we show our calculated dipole moment components along with the experimental values, whenever available. Table 3 depicts that for most of the cases our estimated total dipole moments are in good agreement with the experimentally available data. In case of E-ethanimine of the ${{\rm{C}}}_{2}{{\rm{H}}}_{5}{\rm{N}}$ isomeric group, we found a maximum deviation of 11.5% between our calculated and experimental values of total dipole moments. On an average, we found a $5.35 \%$ deviation between our calculated and experimental values.

Table 3. Calculated Dipole Moment Components for All Species of Six Isomeric Groups with the HF/6-31G(3df) Method

Number	Species	${\mu }_{a}$ (D)	${\mu }_{b}$ (D)	${\mu }_{c}$ (D)	${\mu }_{{tot}}$ (D)
${\mathrm{CH}}_{3}{\rm{N}}$ Isomeric Group

1	Methanimine	−1.5115 (−1.300^a)	−1.4556 (−1.500^a)	0.0000 (0.000^a)	2.0985 (2.000^a)
2	${\lambda }^{1}$ -Azanylmethane	−1.9499	−0.0176	0.1483	1.9556

${\mathrm{CH}}_{5}{\rm{N}}$ Isomeric Group

1	Methylamine	0.4410	0.2771	1.1774	1.2874 (1.310^b)

${{\rm{C}}}_{2}{{\rm{H}}}_{5}{\rm{N}}$ Isomeric Group

1	(E)-Ethanimine	0.2063	−2.0884	0.2912	2.1187 (1.900^b)
2	(Z)-Ethanimine	0.6062	−2.3957	0.5926	2.5412
3	Ethenamine	0.5514	1.0539	−0.7109	1.3857
4	N-Methylmethanimine	−0.2812	1.0514	1.2499	1.6573 (1.530^c)
5	Aziridine	1.6649	−0.2522	0.1768	1.6931 (1.90 ± 0.01^b)

${{\rm{C}}}_{2}{{\rm{H}}}_{7}{\rm{N}}$ Isomeric Group

1	Ethylamine (trans)	0.8802	−0.1949	0.8894	1.2664 (1.304 ± 0.011^b)
2	Ethylamine (gauche)	−0.5839	−1.0489	−0.2731	1.2312 (1.220^b)
3	Dimethylamine	0.1499	−0.9771	−0.1444	0.9991 (1.030^b)

${{\rm{C}}}_{3}{{\rm{H}}}_{7}{\rm{N}}$ Isomeric Group

1	2-Propanimine	−0.8107	1.8357	1.4047	2.4495
2	2-Propenamine	0.4017	0.4670	−1.1975	1.3467
3	(1E)-1-Propanimine	−1.0918	−1.5598	0.8831	2.0987
4	(1Z)-1-Propen-1-amine	−0.1209	1.0920	1.7882	2.0987
5	(1E)-N-Methylethanimine	−1.3457	−0.2385	0.8994	1.6360
6	(1Z)-1-Propanimine	−2.1065	1.5775	−0.0300	2.6318
7	(1E)-1-Propen-1-amine	1.0898	−0.4583	−0.2748	1.2138
8	N-Ethylmethanimine	−1.4418	−0.6595	−0.0489	1.5862
9	N-Methylethenamine	−1.2679	−0.0583	−0.0886	1.2723
10	Allylamine	−0.1645	−1.1175	−0.2388	1.1545 (≈1.2^b)
11	Cyclopropanamine	0.0564	0.9405	−0.8402	1.2624 (1.190^a)
12	S-2-Methylaziridine	1.3228	0.6207	0.7330	1.6347
13	(2S)-2-Methylaziridine	0.5335	0.4331	1.4840	1.6354
14	2-Methylaziridine (trans)	0.6744	0.0897	−1.4863	1.6346 (1.57 ± 0.03^b)
15	2-Methylaziridine (cis)	0.6744	0.0897	−1.4863	1.6346 (1.77 ± 0.09^b)
16	Azetidine	0.2802	0.2805	1.1993	1.2632
17	Methylaziridine	0.8549	0.1523	0.9647	1.2980
18	N-methylethanamine	−0.5108	−1.0613	0.4630	1.2655
19	(Dimethyliminio)methanide	−1.4791	−2.9791	0.3350	3.3429

${{\rm{C}}}_{3}{{\rm{H}}}_{9}{\rm{N}}$ Isomeric Group

1	2-Aminopropane	−0.0991	−0.3068	1.1727	1.2162 (1.190^d)
2	Propylamine	−0.9663	0.5630	0.3766	1.1800 (1.170^b)
3	Ethylmethylamine	0.1756	0.2227	−0.8964	0.9402
4	Trimethylamine	0.1174	0.1270	−0.6598	0.6821 (0.612^b)

Notes. Experimental values are shown in parentheses.

^aDemaison et al. (1974). ^bNelson et al. (1967). ^cSastry & Curl (1964). ^dMehrotra et al. (1977).

Download table as: ASCII Typeset image

As mentioned earlier, the rotational spectroscopy is the most convenient and the most reliable method for detecting molecules in the ISM. Quantum chemical studies have succeeded in providing reliable spectroscopic constants to aid laboratory microwave studies. Accurate quantum chemical studies of rotational transition frequencies may lead to interstellar detections with confidence. Calculations of the rotational level need high-level basis sets for accurate estimations of structure, spectrum, and for optimization to obtain the ground-state energy. We use the MP2 perturbation method with the 6–311++G(d,p) basis set, which is capable of producing spectroscopic constants close to the experimental values. Corrections for the interaction between rotational motion and vibrational motion, along with corrections for vibrational averaging and anharmonic corrections to the vibrational motion, are also considered in our calculations. In Table 4 we summarize our calculated theoretical values of rotational constants for all the species considered here. A comparison with the existing experimental results, whenever available, is also made. These spectroscopic constants can be used to generate catalog files of spectroscopic frequencies by using the SPCAT program (Pickett 1991) in the JPL/CDMS format. Table 4 also contains the rotational partition function of a temperature relevant to the hot-core condition (∼200 K). Among all the species considered here, ${\lambda }^{1}$ -azanylmethane is a prolate symmetric top and trimethylamine is an oblate symmetric top, and both have three rotational symmetries. The rest of the species in this study are asymmetric top having rotational symmetry 1. We calculate the rotational partition function for the asymmetric top species by

$\begin{eqnarray*}&&{Q}_{\mathrm{rot}}=5.3311\times {10}^{-6}\sqrt{(}{T}^{3}/{ABC})/\sigma ,\end{eqnarray*}$

where σ is the rotational symmetry number. The rotational partition function for the prolate symmetric top molecule is calculated by

$\begin{eqnarray*}&&{Q}_{\mathrm{rot}}=5.3311\times {10}^{-6}\sqrt{(}{T}^{3}/{B}^{2}A)/\sigma .\end{eqnarray*}$

For the oblate symmetric top molecule, the rotational partition function is calculated as

$\begin{eqnarray*}&&{Q}_{\mathrm{rot}}=5.3311\times {10}^{-6}\sqrt{(}{T}^{3}/{A}^{2}C)/\sigma .\end{eqnarray*}$

Table 4. Calculated Rotational Constants and Rotational Partition Functions at 200 K for All Species of Six Isomeric Groups (with the MP2/6-311++G(d,p) Method)

Number	Species	A (in GHz)	B (in GHz)	C (in GHz)	Rotational Partition
					Function at 200 K
${\mathrm{CH}}_{3}{\rm{N}}$ Isomeric Group

1	Methanimine	195.72173 (196.21116^a)	34.45869 (34.64252^a)	29.30013 (29.35238^a)	0.107265(+04)
2	${\lambda }^{1}$ -Azanylmethane	157.58498	27.56460	27.56460	0.459337(+03)

${\mathrm{CH}}_{5}{\rm{N}}$ Isomeric Group

1	Methylamine	103.42705 (103.12861^b)	22.75135 (22.62234^b)	21.85872 (21.69598^b)	0.210246(+04)

${{\rm{C}}}_{2}{{\rm{H}}}_{5}{\rm{N}}$ Isomeric Group

1	(E)-Ethanimine	52.91394 (52.83537^a)	9.76090 (10.07601^a)	8.68503 (8.70427^a)	0.711944(+04)
2	(Z)-Ethanimine	50.17305 (49.5815^a)	9.76932 (10.15214^a)	8.61433 (8.644814^a)	0.733810(+04)
3	Ethenamine	55.91347	9.98960	8.55386	0.689840(+04)
4	N-Methylmethanimine	51.70697 (52.52375^a)	10.71490 (10.66613^a)	9.39306 (9.37719^a)	0.660982(+04)
5	Aziridine	22.81302 (22.73612^c )	21.19888 (21.19238^c)	13.43101 (13.38307^c)	0.591642(+04)

${{\rm{C}}}_{2}{{\rm{H}}}_{7}{\rm{N}}$ Isomeric Group

1	Ethylamine (trans)	31.90275 (31.75833^d)	8.75819 (8.749157^d)	7.82305 (7.798905^d)	0.101989(+05)
2	Ethylamine (gauche)	32.46287 (32.423470^e)	8.99003 (8.942086^e)	7.86715 (7.825520^e)	0.995128(+04)
3	Dimethylamine	34.22904 (34.24222^f)	9.38988 (9.33403^f)	8.26707 (8.21598^f)	0.925036(+04)

${{\rm{C}}}_{3}{{\rm{H}}}_{7}{\rm{N}}$ Isomeric Group

1	2-Propanimine	9.64694	8.48897	4.78348	0.240917(+05)
2	2-Propenamine	9.54753	8.97855	4.79187	0.235267(+05)
3	(1E)-1-Propanimine	23.30832	4.33503	4.20885	0.231221(+05)
4	(1Z)-1-Propen-1-amine	23.30833	4.33547	4.20908	0.231203(+05)
5	(1E)-N-Methylethanimine	38.04146	4.07938	3.86089	0.194801(+05)
6	(1Z)-1-Propanimine	23.19882 (24.1852684^g)	4.28693(4.2923639^g)	4.17097 (4.1567893^g)	0.234119(+05)
7	(1E)-1-Propen-1-amine	38.31516	3.85080	3.59371	0.207076(+05)
8	N-Ethylmethanimine	24.05782	4.60272	4.48201	0.214037(+05)
9	N-Methylethenamine	32.00012	4.30235	4.04446	0.202070(+05)
10	Allylamine	23.65103	4.23494	4.17205	0.233259(+05)
11	Cyclopropanamine	16.28786 (16.26995^h)	6.72692 (6.72300^h)	5.80201 (5.79533^h)	0.189118(+05)
12	S-2-Methylaziridine	16.91977	6.53608	5.76664	0.188818(+05)
13	(2S)-2-Methylaziridine	16.91889	6.53525	5.76592	0.188847(+05)
14	2-Methylaziridine (trans)	16.92200	6.53613	5.76677	0.188803(+05)
15	2-Methylaziridine (cis)	16.68599	6.56078	5.81794	0.188940(+05)
16	Azetidine	11.54225	11.36812	6.70581	0.160748(+05)
17	Methylaziridine	16.41594	7.25710	6.19112	0.175575(+05)
18	N-methylethanamine	36.98588	4.14324	3.84501	0.196438(+05)
19	(Dimethyliminio)methanide	10.15847	9.14934	5.12560	0.218464(+05)

${{\rm{C}}}_{3}{{\rm{H}}}_{9}{\rm{N}}$ Isomeric Group

1	2-Aminopropane	8.37627 (8.33183ⁱ)	7.99371 (7.97718ⁱ)	4.67889 (4.63719ⁱ)	0.269396(+05)
2	Propylamine	25.18613	3.74012	3.49778	0.262689(+05)
3	Ethylmethylamine	26.06033	3.92898	3.67799	0.245712(+05)
4	Trimethylamine	8.75934	8.75934	4.99056	0.812259(+04)

Notes. Experimentally obtained rotational constants are shown in parentheses.

^aPearson & Lovas (1977). ^bHerzberg (1966). ^cBak & Skaarup (1971). ^dFischer & Botskor (1982). ^eFischer & Botskor (1984). ^fWollrab & Laurie (1968). ^gMargulès et al. (2015). ^hHendricksen & Harmony (1969). ⁱMehrotra et al. (1977).

Download table as: ASCII Typeset image

2.2. Chemical Modeling

Our large gas-grain chemical model (Das et al. 2008a, 2013a, 2013b; Majumdar et al. 2014a, 2014b; Das et al. 2015a, 2015b; Gorai et al. 2017a, 2017b) is employed for the purpose of chemical modeling. We assume that gas and grains are coupled through accretion and thermal/nonthermal desorption. Unless otherwise stated, a moderate value of the nonthermal desorption factor of ∼0.03 is assumed as mentioned in Garrod et al. (2007). A visual extinction of 150 and a cosmic-ray ionization rate of $1.3\times {10}^{-17}\,{{\rm{s}}}^{-1}$ are used. The initial condition is adopted from Leung et al. (1984). In order to mimic actual physical conditions of the star-forming region, we consider the warm-up method that was established by Garrod & Herbst (2006). Initially, we assume that the cloud remains in isothermal (T = 10 K) phase for 10⁶ yr, which is then followed by a subsequent warm-up phase where the temperature can gradually increase up to 200 K in 10⁵ yr. Hence, our simulation time is restricted to $1.1\times {10}^{6}$ yr. We assume that each phase has the same constant density ( ${n}_{H}={10}^{7}$ cm⁻³).

Our gas phase chemical network is principally adopted from the UMIST 2012 database (McElroy et al. 2013). For the grain surface reaction network, we primarily follow Ruaud et al. (2016). In addition to the above network, our network includes some reactions that are needed for the formation/destruction of interstellar amines and aldimines. Ice phase formation of some of the amines and aldimines that are considered here is shown in Table 1. Similar pathways are also considered for the formation of these species in the gas phase.

For the computation of the gas phase rate coefficients of some additional gas phase neutral–radical (NR) reactions with a barrier, we use the transition state theory (TST), which leads to the Eyring equation (Eyring 1935):

$\begin{eqnarray}&&k=({K}_{B}T/{hc})\exp (-{\rm{\Delta }}G\ddagger/{RT})\ {{\rm{s}}}^{-1},\end{eqnarray} \tag{ 1 }$

where ${\rm{\Delta }}G\ddagger$ is the Gibbs free energy of activation and c is the concentration, which is set to 1. ${\rm{\Delta }}G\ddagger$ is calculated by the quantum chemical calculation (QST2 method with B3LYP/6-311++G(d,p)). Equation (1) depicts that the rate coefficient is exponentially increasing with the temperature. Thus, to avoid any unattainable rate coefficient around the high-temperature domain, we use an upper limit (10⁻¹⁰ cm³s⁻¹) for Equation (1).

Normally, a radical–radical addition reaction with a single product can occur through the radiative association. Vasyunin & Herbst (2013) outlined the rate coefficient for the formation of larger molecules by gas phase radiative association reactions. According to them, a larger molecule such as ${\mathrm{CH}}_{3}{\mathrm{OCH}}_{3}$ can be formed by

$\begin{eqnarray*}&&{\mathrm{CH}}_{3}+{\mathrm{CH}}_{3}{\rm{O}}\to {\mathrm{CH}}_{3}{\mathrm{OCH}}_{3}+\mathrm{Photon}.\end{eqnarray*}$

They considered the following temperature-dependent rate coefficient for the above reaction:

$\begin{eqnarray*}&&k={10}^{-15}{(T/300)}^{-3}.\end{eqnarray*}$

In our work, we also consider similar rate coefficients for the radical–radical gas phase reactions leading to a single product. In our model, we consider the formation and destruction of these species in both phases.

To compute the rate coefficients of ice phase reaction pathways, we use diffusive reactions with a barrier against diffusion ( $\kappa \times {R}_{\mathrm{diff}}$ ), which is based on thermal diffusion (Hasegawa et al. 1992). κ is the quantum mechanical probability of tunneling through a rectangular barrier of thickness d. κ is unity in the absence of a barrier. For reactions with activation energy barriers (E_a), κ is defined as the quantum mechanical probability for tunneling through the rectangular barrier of thickness d ( $=1\,\mathring{\rm A}$ ) and is calculated by

$\begin{eqnarray}&&\kappa =\exp [-2{(d/{\hslash })(2\mu {E}_{a})}^{1/2}].\end{eqnarray} \tag{ 2 }$

Chemical enrichment of interstellar grain mantles depends on the desorption energies (E_d) and barriers against diffusion (E_b) of the adsorbed species. In the low-temperature regime, the mobility of the lighter species such as ${\rm{H}},\ {\rm{D}},\ {\rm{N}}$ , and ${\rm{O}}$ mainly controls the chemical composition of the interstellar grain mantle. Composition of the grain mantle under the low-temperature regime is already discussed on several occasions (Chakrabarti et al. 2006a, 2006b; Das et al. 2008b, 2010; Das & Chakrabarti 2011; Sahu et al. 2015; Das et al. 2016; Sil et al. 2017). Here we use ${E}_{b}=0.50{E}_{d}$ (Garrod 2013). Binding energies are mostly taken from the KIDA database. Binding energy of some of the newly added ice phase species was not available in the KIDA database. For these species, we have added the binding energies of the reactants, which are required for the formation of these species. A similar technique was also employed in Garrod (2013). For example, for the calculation of the binding energy of ${\mathrm{CH}}_{3}\mathrm{CNH}$ , we add the binding energies of ${\mathrm{CH}}_{3}\mathrm{CN}$ and H.

For the destruction of gaseous amines and aldimines, we assume various ion-neutral (IN) and photodissociative pathways. Various IN and photodissociative destruction pathways were already available in Quan et al. (2016) (for ethanimine) and McElroy et al. (2013) (for methanimine). We follow similar pathways and the same rate coefficients for the destructions of other amines, aldimines, and their associated species. In the Appendix, we point out all the gas phase formation and destruction reactions that are considered here. In analogy, for the destruction of ice phase amines, aldimines, and their associated neutrals, we assume similar photodissociative reactions. Rate coefficients for the photodissociative reactions are assumed to be the same in both phases. Abundances of the gas phase species can also decrease via adsorption onto the ice. However, the reverse process of desorption also occurs.

3. Results and Discussions

In this section, the results of high-level quantum chemical calculations, together with our chemical model, are presented and discussed. A detailed discussion of each isomeric group is given below.

3.1. CH₃N Isomeric Group

This group contains two molecular species (Figure 1), methanimine and ${\lambda }^{1}$ -azanylmethane. Methanimine ( ${\mathrm{CH}}_{2}\mathrm{NH}$ ) has already been observed long ago using the Parkes 64 m telescope in Sgr B2 (Godfrey et al. 1973). However, the presence of ${\lambda }^{1}$ -azanylmethane is yet to be ascertained. Based on the enthalpy of formation and relative energy values shown in Table 2, methanimine appears to be the most stable candidate of the ${\mathrm{CH}}_{3}{\rm{N}}$ isomeric group. But enthalpy of formation is not sufficient enough to dictate the abundance of this species specifically when the system is far away from the equilibrium. It is only the reaction pathways that can dictate the final abundance of any species in the ISM. Our calculated dipole moment components (shown in Table 3) of methanimine are very close to the available experimental values. From our calculated dipole moment components, it is found that for methanimine "a" and "b" type rotational transitions are the strongest, whereas "c" type transitions are absent. In the case of ${\lambda }^{1}$ -azanylmethane, the strongest component of dipole moment is found to be the "a" component, whereas the "b" component is found to be the weakest. The average dipole moment component of methanimine is found to be slightly higher than that of ${\lambda }^{1}$ -azanylmethane. Our calculated rotational constants for methanimine are also shown in Table 4, which are found to be very close to the prevailing experimental values.

**Figure 1.** ${\mathrm{CH}}_{3}{\rm{N}}$ isomers.
Download figure:
Standard image High-resolution image

It is believed that the methanimine is primarily created within the cold ice phase. The dominated pathways are shown in the reaction range R4–R7 of Table 1. Starting with the cyanide radical, ${\mathrm{CH}}_{2}\mathrm{NH}$ may form through the successive hydrogen addition reaction in ice phase. Subsequent hydrogen addition may take place in two ways: hydrogen addition with HCN could result in ${{\rm{H}}}_{2}\mathrm{CN}$ (R4) or HCNH (R5). Woon (2002) pointed out that reactions R4 and R5 possess activation energy barriers of about 3647 and 6440 K, respectively. ${{\rm{H}}}_{2}\mathrm{CN}$ and HCNH can further produce ${\mathrm{CH}}_{2}\mathrm{NH}$ by the hydrogen addition reaction (R6 and R7, respectively). The surface network of KIDA already considered the reactions enlisted in Graninger et al. (2014), and thus HCN/HNC-related chemistry is consistent. The gas phase pathways of Graninger et al. (2014) are also considered in our gas phase network. Near the higher temperatures, methanimine may be produced by the decomposition of methylamine ( ${\mathrm{CH}}_{3}{\mathrm{NH}}_{2}$ ; Johnson & Lovas 1972). Recently, Suzuki et al. (2016) pointed out that this species could be produced on the interstellar ice by other reactions (R1–R3) shown in Table 1.

For the gas phase reactions G4 and G5 of Table 5, we obtain ${\rm{\Delta }}G\ddagger$ of 8.37 and 10.06 Kcal/mol, respectively. In Figures 2(a) and (b), we show the chemical evolution of methanimine within the cold isothermal phase, and in Figure 3 the subsequent warm-up phase is shown. Abundances are shown with respect to ${{\rm{H}}}_{2}$ molecules. It is clear that during the isothermal phase methanimine is significantly abundant in both phases and has a peak abundance of $5.93\times {10}^{-08}$ in gas phase and $3.49\times {10}^{-06}$ in the ice phase. A strong decreasing slope of gas phase methanimine is observed from Figures 2(a) and (b), which also depict a decreasing slope (during the end of the isothermal regime) of ice phase methanimine due to the production of methylamine by successive hydrogen addition reactions (R8–R9). Dashed curves in Figure 2(a) are shown for the gas phase abundances of all the aldimines and amines for the case where nonthermal desorption factor a_fac is assumed to be 0. The gas phase abundances of methanimine with ${a}_{\mathrm{fac}}=0$ (dashed line in Figure 2(a)) and ${a}_{\mathrm{fac}}=0.03$ (solid line in Figure 2(a)) differ significantly. This is because in the isothermal phase the gas phase contribution of methanimine is mainly coming from the ice phase via the nonthermal desorption mechanism. Following the KIDA database, the desorption energy of methanimine is assumed to be 5534 K. It is evident that in the warm-up phase sublimation of methanimine occurs around 110K. In the warm-up phase (Figure 3), abundance of gas phase methanimine is significantly increased owing to the efficient gas phase formation by reactions G1–G7. Peak abundance of gas phase methanimine is found to be around $1.81\times {10}^{-09}$ . Our obtained values can be compared with the recent hot-core observation of methanimine of $\sim 7.0\times {10}^{-08}$ in G10.47+0.03 and $3.0\times {10}^{-9}$ in NGC 6334F by Suzuki et al. (2016).

**Figure 2.** Chemical evolution of the aldimines and amines in the isothermal phase for ${a}_{\mathrm{fac}}=0.03$ (solid) and 0 (dashed).
Download figure:
Standard image High-resolution image

**Figure 2.** Chemical evolution of the aldimines and amines in the isothermal phase for ${a}_{\mathrm{fac}}=0.03$ (solid) and 0 (dashed).
Download figure:
Standard image High-resolution image

**Figure 3.** Chemical evolution of the aldimines and amines in the warm-up phase. Solid lines represent the gas phase species, whereas corresponding dashed lines represent the ice phase species.
Download figure:
Standard image High-resolution image

3.2. CH₅N Isomeric Group

Only methylamine ( ${\mathrm{CH}}_{3}{\mathrm{NH}}_{2}$ ) belongs to this isomeric group (Figure 4), and this was already observed long ago in Sgr B2 and Ori A (Fourikis et al. 1974; Kaifu et al. 1974). In Table 2, we compare our calculated enthalpies of formation with that of the existing experimental value. We find that our calculated value with the B3LYP/6-31G(d,p) method is closer to the experimentally obtained value than that computed from the G4 composite method. Methylamine is the precursor of an amino acid (glycine) formation. Takagi & Kojima (1973) and Kaifu et al. (1974) found that the c-type transitions of methylamine are four times stronger than the a-type transitions. We also found a very strong c-component of dipole moment shown in Table 3. The calculated total dipole moment component for methylamine is 1.2874 D, whereas the experimentally obtained value is 1.31 ± 0.03 D (Table 3). Also, a very good correlation between our calculated rotational constants and experimentally obtained values can be seen from Table 4.

**Figure 4.** ${\mathrm{CH}}_{5}{\rm{N}}$ isomer.
Download figure:
Standard image High-resolution image

In the ISM, methylamine may be formed via two successive hydrogen addition reactions of methanimine in the ice phase (Godfrey et al. 1973; Suzuki et al. 2016). Woon (2002) determined that the primary step of this hydrogen addition reaction may proceed in two ways. First, hydrogenation of methanimine yields ${\mathrm{CH}}_{3}\mathrm{NH}$ (R8) having an activation barrier of 2134 K; second, it may produce ${\mathrm{CH}}_{2}{\mathrm{NH}}_{2}$ (R9) having an activation barrier of 3170 K. Reactions R8 and R9 may also occur in the gas phase. From our TST calculation, we have ${\rm{\Delta }}G\ddagger=7.84$ Kcal/mol for reaction G8 of Table 5. However, we did not find a suitable transition state for gas phase reaction G9 of Table 5. In the ice phase, R9 possesses a higher activation barrier (1.485 times higher) than R8. We assume that a similar trend would be followed for the gas phase reaction G9, and so we assume ${\rm{\Delta }}G\ddagger=11.64$ Kcal/mol for gas phase reaction G9. Methylamine may further be produced by the hydrogenation reaction of these two products by reactions R10 and R11, respectively. Woon (2002) recommended that the simplest amino acid, glycine, may be formed by the reaction between ${\mathrm{CH}}_{2}{\mathrm{NH}}_{2}$ and the COOH radical. So, methylamine is an important product toward the formation of glycine.

Since reactions G8 and G9 possess high ${\rm{\Delta }}G\ddagger$ , during the isothermal phase production of gas phase methylamine is inadequate. However, despite a high activation barrier ( ${E}_{{\rm{a}}}$ ), reactions R8 and R9 would be efficiently processed on interstellar ice by quantum mechanical tunneling and populate the gas phase by the nonthermal desorption. Mainly due to the nonthermal chemical desorption phenomenon, ice phase methylamine populates the gas phase. It is clearly visible from Figure 2(a) that for the case of ${a}_{\mathrm{fac}}=0$ the gas phase contribution of methylamine is negligible (the dashed line corresponding to the methylamine is absent in Figure 2(a)), Hence, in the isothermal phase, the contribution for the gas phase methylamine mainly comes from the ice phase. We find that in the isothermal phase methylamine attains a peak value of $8.46\times {10}^{-13}$ in the gas phase and $3.70\times {10}^{-08}$ in the ice phase. From Figure 3, we observe that the ice phase abundance initially increases owing to the increase in the mobility of the reactants. Peak ice phase abundance of methylamine is obtained to be $5.44\times {10}^{-07}$ . Near the high temperature, production of gas phase methylamine significantly contributed as a result of (a) the enhancement of the temperature-dependent rate coefficient of reactions G8 and G9 and (b) the increase in the gas phase methanimine formation. The peak gas phase abundance of methylamine is found to be $5.54\times {10}^{-07}$ . Our obtained values may be compared with the recent observation of methylamine (Ohishi et al. 2017). They predicted methylamine abundance of $\sim 1.2\times {10}^{-08}$ in G10.47+0.03.

3.3. C₂H₅N Isomeric Group

Five isomers belong to this isomeric group (Figure 5): E-ethanimine, Z-ethanimine, ethenamine, N-methylmethanimine, and aziridine. Out of these five isomers, recently both conformers (E and Z) of ethanimine ( ${\mathrm{CH}}_{3}\mathrm{CHNH}$ ) had been detected in Sgr B2 (Loomis et al. 2013). From our quantum chemical calculation, we found that E-ethanimine is energetically more stable (4.35 KJ/mol by using MP2/6-311G++(d,p) and 1.2 KJ/mol by using the G4 composite method) than Z-ethanimine. Quan et al. (2016) and Loomis et al. (2013) obtained an energy difference of 4.60 and 4.24 KJ/mol, respectively, between these two conformers. We have shown the enthalpy of formation values for all the species in Table 2, along with the experimentally obtained values, where available. Our calculated enthalpies of formation using the B3LYP/6-31G(d,p) method are in good agreement with the experimentally obtained values of E-ethanimine, n-methylmethanimine, and aziridine. For a better assessment, in Figure 6 we show the enthalpy of formation with the molecule number noted in Table 2 and Figure 5 for the ${{\rm{C}}}_{2}{{\rm{H}}}_{5}{\rm{N}}$ isomeric group. Clearly, E-ethanimine has the minimum enthalpy of formation followed by Z-ethanimine. The energy difference between these two is smaller than the other isomers of this isomeric group. Observed isomers are marked as green circles in Figures 6 and 7, and the unobserved isomers are marked as red circles.

**Figure 5.** ${{\rm{C}}}_{2}{{\rm{H}}}_{5}{\rm{N}}$ isomers.
Download figure:
Standard image High-resolution image

**Figure 6.** Enthalpy of formation of the ${{\rm{C}}}_{2}{{\rm{H}}}_{5}{\rm{N}}$ isomeric group. Molecules already observed are marked as green circles, and those yet to be observed are marked as red circles.
Download figure:
Standard image High-resolution image

**Figure 7.** Expected intensity ratio of the ${{\rm{C}}}_{2}{{\rm{H}}}_{5}{\rm{N}}$ isomeric group by considering three components of the dipole moment and effective dipole moment of all species.
Download figure:
Standard image High-resolution image

All the dipole moment components are presented in Table 3. It is found that in both the cases (E and Z) a b-type transition dominates. Our calculated values of dipole moments are compared with the existing values (Lovas et al. 1980; Lias et al. 2005). The effective dipole moment of Z-ethanimine is found to be higher than that of E-ethanimine. Charnley et al. (1995) pointed out that for an optically thin emission, a estimate of the antenna temperature could be made by calculating the intensity of a given rotational transition. This intensity is proportional to ${\mu }^{2}/Q({T}_{\mathrm{rot}})$ , where μ is the electric dipole moment and $Q({T}_{\mathrm{rot}})$ is the partition function at rotational temperature (T_rot). In Table 4, we have pointed out the rotational constants and the rotational partition function at ${T}_{\mathrm{rot}}=200$ K. In Figure 7, we have shown the plot of the expected intensity ratio (by assuming that all the species of this isomeric group have the same abundances) with respect to the most stable isomer (E-ethanimine) of this isomeric group (relative energy values with molecule number of all isomers of the ${{\rm{C}}}_{2}{{\rm{H}}}_{5}{\rm{N}}$ isomeric group noted in Table 2). In Figure 7, the expected intensity ratios for all the species of this isomeric group are shown by considering the three components of the dipole moment along with the effective dipole moments. Since in this isomeric group Z-ethanimine has the largest effective dipole moment, assuming the same abundances, the probability of detecting the Z isomer of ethanimine will be more favorable than the other isomers of this isomeric group. From Figure 7, we can see that after E and Z isomers of ethanimine, aziridine has the strongest transition, but due to its higher relative energy in comparison to E-ethanimine, it is the less probable candidate (if reaction pathways do not influence it at all) for astronomical detection.

Loomis et al. (2013) mentioned that ice phase ethanimine may be produced via two consecutive hydrogen addition reactions with ${\mathrm{CH}}_{3}\mathrm{CN}$ . Quan et al. (2016) recently proposed that the first step (R14) of the hydrogen addition reaction with ${\mathrm{CH}}_{3}\mathrm{CN}$ has a barrier of 1400 K and the second step (R15) is a radical–radical reaction and assumed to be barrier-less in nature. For the gas phase reaction of G14 of Table 5, our calculated value of ${\rm{\Delta }}G\ddagger$ is 10.32 Kcal/mol. Quan et al. (2016) additionally suggested that ethanimine can even be produced by the reaction between ${\mathrm{CH}}_{3}$ and ${{\rm{H}}}_{2}\mathrm{CN}$ in ice phase. Among the gas phase pathways, reaction between ${{\rm{C}}}_{2}{{\rm{H}}}_{5}$ and NH (reaction G23 of Table 5) may lead to ${\mathrm{CH}}_{3}\mathrm{CHNH}$ . In our network, we include all the gas phase reactions mentioned in Table 5 and ice phase reactions shown in Table 1. For the gas phase barrier-less reactions, a conservative value of the rate coefficient (Vasyunin & Herbst 2013) is considered. Here, we assume only one form of ethanimine (E-ethanimine) for the purpose of our modeling.

In Figures 2(a) and (b), we have shown the chemical evolution of ethanimine in the isothermal phase, and subsequently the warm-up phase is shown in Figure 3. In the isothermal phase, ethanimine has the peak value of $4.99\times {10}^{-13}$ in the gas phase and $2.69\times {10}^{-08}$ in the ice phase. During the warm-up phase, gas phase ethanimine has a peak value of $3.17\times {10}^{-08}$ . In the warm-up phase, gas phase production of ethanimine is also contributing owing to the enhancement of the temperature-dependent rate coefficient of reaction G14. Around 125 K, the abundance of ethanimine attains a peak and starts to decrease owing to the efficient production of ethylamine by the successive hydrogenation reactions (R17–R18). Since reaction R17 has a barrier, we use Equation (1) for the computation of its rate coefficient. Equation (1) clearly says that as we are increasing the temperature, the rate coefficient increases exponentially. Thus, in the warm-up phase, the rate coefficient of reaction G17 increases exponentially and attains a reasonable rate (10⁻¹⁰ cm³ s⁻¹), which means that the destruction of ethanimine by the hydrogenation reaction also gradually increases and attains a quasi-steady state. At the end of our simulation (after $1.1\times {10}^{6}$ yr), we note an abundance of $1.27\times {10}^{-12}$ for Z-ethanimine, whereas the predicted abundance of Z-ethanimine is $\sim 6.0\,\times {10}^{-11}$ from Quan et al. (2016).

3.4. C₂H₇N Isomeric Group

Trans-ethylamine, gauche-ethylamine, and dimethylamine belong to the ${{\rm{C}}}_{2}{{\rm{H}}}_{7}{\rm{N}}$ isomeric group (Figure 8). Interestingly, no species of this isomeric group is yet to be detected in the ISM. However, the presence of ethylamine was traced in comet Wild 2 (Glavin et al. 2008). Ethylamine is the precursor of simple amino acid glycine. It can exist in the form of two stable conformers: gauche and trans. An experiment by Hamada et al. (1986) shows that the trans conformer is slightly more stable than the gauche conformer. Our calculated values are also in line with this result. We obtained that the gauche conformer has 1.67 KJ/mol higher energy than the trans conformer. Hence, according to the enthalpy of formation and relative energies as shown in Table 2, trans-ethylamine has the least enthalpy of formation and is most stable among this isomeric group. In Figure 9, the enthalpy of formation of this isomeric group is depicted with the molecule number, and the enthalpy of formation is noted in Table 2. In comparison with the experimentally measured enthalpies of formation, the G4 composite method overestimates the enthalpy of formation values for ethylamine and dimethylamine.

**Figure 9.** Enthalpy of formation of the ${{\rm{C}}}_{2}{{\rm{H}}}_{7}{\rm{N}}$ isomeric group.
Download figure:
Standard image High-resolution image

In the case of the trans conformer of ethylamine, components a and c of dipole moments are stronger, whereas for the gauche form, the b-component is found to be the strongest. For dimethylamine also the b-component of the dipole moment dominates and the a and b components have minor contributions. Based on the data available from our quantum chemical calculations, in Figure 10 we have shown the expected intensity ratio with respect to the species having the least enthalpy of formation. Figure 10 depicts that the trans-ethylamine has the highest expected intensity ratio (∼1) in comparison with the other two members (gauche-ethylamine has 0.97 and dimethylamine has 0.69) of this isomeric group, and thus trans-ethylamine has the highest probability of its astronomical detection from this isomeric group.

**Figure 10.** Expected intensity ratio of the ${{\rm{C}}}_{2}{{\rm{H}}}_{7}{\rm{N}}$ isomeric group by considering three components of the dipole moment and effective dipole moment of all the species.
Download figure:
Standard image High-resolution image

Ethylamine could be formed on the grain surface via two successive hydrogen additions of ethanimine. Our calculation reveals that the first step of this hydrogenation reaction has an activation barrier of 1846 K (R17). For the gas phase hydrogenation reaction (G17), our calculated ${\rm{\Delta }}G\ddagger$ parameter is found to be 9.98 Kcal/mol. Since the second step of this reaction is radical–radical in nature, we assume that reaction R18 may be treated as a barrier-less process. Gas and ice phase abundances of ethylamine in the isothermal phase are depicted in Figures 2(a) and (b). In the isothermal phase, we have a peak gas phase abundance of $1.19\times {10}^{-16}$ and in the ice phase $1.99\times {10}^{-09}$ . In the warm-up phase (Figure 3), ice phase abundance roughly remains invariant up to 125 K and then starts to decrease sharply. Its gas phase abundance is higher and has a peak abundance of $3.98\times {10}^{-08}$ .

In terms of the size of the molecule, ethanimine is more complex than methanimine. Similarly to their successors, ethylamine is more complex than methylamine. Hence, it may be expected that throughout the evolutionary stage the abundances of ethanimine/ethylamine would be always less than that of methanimine/methylamine. But Figures 2(a), 2(b), and 3 depict that this trend is not universal for all circumstances. This is due to the fact that the formation of methanimine and its successor and the formation of ethanimine and its successor are processed through totally different channels. Their destruction rates are also different. For example, ice phase formation of methanimine mainly occurs by successive hydrogenation reactions with HCN (reactions R4 to R7), whereas ethanimine formation is mainly controlled by successive hydrogenation reactions with CH₃CN (reactions R14 and R15). Now, reactions R4 and R5 contain a much higher barrier than that of the reaction R14. Since HCN is more abundant than CH₃CN, despite high barriers involved in the formation of methanimine, in the isothermal stage, most of the time, ice phase abundance of methanimine remains higher than in ethanimine. In the hot-core region, due to the lower activation barrier of reaction R14, ethanimine formation becomes more favorable. Now, methylamine is forming from methanimine (by reactions R8–R10) and ethylamine is forming from ethanimine (by reactions R17–R18). Once again, the activation barrier involved in the case of methylamine formation (reaction R9) is higher than the barrier involved in the formation of ethylamine (reaction R17). Since very complex chemistry is going on, abundances of these species should be compared very carefully.

Altwegg et al. (2016) showed that in 67P/Churyumov–Gerasimenko relative abundance between methylamine and glycine is 1.0 ± 0.5 and the ethylamine-to-glycine ratio is 0.3 ± 0.2. Taking the maximum and minimum values from this observation, we can see that the methylamine-to-ethylamine ratio may vary in the range of $\sim 1-15$ . In order to check the correlation (if any) between the cometary ice as observed by Altwegg et al. (2016) and interstellar ice, we may focus on our ice phase evolution results of the isothermal (T = 10 K) phase. From our modeling results (Figure 2(b)), we found that in the isothermal phase (at time 10⁶ yr) the methylamine-to-ethylamine ratio is ∼17.7 in the ice phase, which is very close to the observed value (Altwegg et al. 2016). This suggests that a more in-depth study is required to confirm this linkage between the interstellar and cometary origins of these molecules.

3.5. C₃H₇N Isomeric Group

Nineteen isomers (Figure 11) belong to the ${{\rm{C}}}_{3}{{\rm{H}}}_{7}{\rm{N}}$ isomeric group. Figure 12 depicts the enthalpy of formation ( ${{\rm{\Delta }}}_{{\rm{f}}}{{\rm{H}}}^{{\rm{O}}}$ ) of this isomeric group. In Table 2 we show the relative energies and enthalpy of formation of various isomers of this isomeric group. Only for cyclopropanamine is experimentally obtained enthalpy of formation available, and this is in close agreement with our calculated enthalpies of formation with the B3LYP/6-31G(d,p) method. Clearly, 2-propanimine is the most stable isomer of this group, followed by 2-propenamine. The next species in this sequence is (1E)-1-propanimine. (1E)-1-propanimine has a lower energy than that of (1Z)-1-propanimine.

**Figure 12.** Enthalpy of formation of the ${{\rm{C}}}_{3}{{\rm{H}}}_{7}{\rm{N}}$ isomeric group.
Download figure:
Standard image High-resolution image

Though (dimethyliminio)methanide (molecule no. 19) has the highest enthalpy of formation and is the least stable of the species in this isomeric group, interestingly, our calculation listed in Table 4 shows that it possesses the highest effective electric dipole moment. (1Z)-1-propanimine (molecule no. 6) is found to have the second-highest effective dipole moment in this isomeric group. However, it is found that the a-type transitions of 1-Z-propanimine are the strongest among all the species of the ${{\rm{C}}}_{3}{{\rm{H}}}_{7}{\rm{N}}$ isomeric group. Figure 13 shows the expected intensity ratio (by considering the three components of the dipole moment along with the effective dipole moment) with respect to the most stable (as well as the species having the least enthalpy of formation) isomer. From Figure 13 it is clear that if the abundances of all these isomeric species are assumed to be the same, then (dimethyliminio)methanide and (1Z)-1-propanimine may be the most probable candidates for astronomical detection from this group. Since (dimethyliminio)methanide is not a very stable species, it does not have a high probability of detection. Thus, based on the stability, enthalpy of formation, and expected intensity ratio, (1Z)-1-propanimine is the most suitable species for future astronomical detection from this isomeric group. However, it is the reaction pathways that can ultimately decide the fate of this species.

**Figure 13.** Expected intensity ratio of the ${{\rm{C}}}_{3}{{\rm{H}}}_{7}{\rm{N}}$ isomeric group by considering three components of the dipole moment and the effective dipole moment of all the species.
Download figure:
Standard image High-resolution image

Methanimine and ethanimine have already been observed in the ISM, and (1Z)1-propanimine may be the next probable candidate for astronomical detection. To the best of our knowledge, the astronomical searches of (1Z)-1-propanimine are yet to be reported in the literature. Hence, (1Z)-1-propanimine remains the best candidate for astronomical observation among all the isomers of the ${{\rm{C}}}_{3}{{\rm{H}}}_{7}{\rm{N}}$ isomeric group.

(1Z)-1-propanimine may be formed via two sequential H addition reactions on ice with propionitrile ( ${\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CN}$ ), where propionitrile may be produced by the radical–radical barrier-less interaction between ${{\rm{C}}}_{2}{{\rm{H}}}_{5}$ and CN. Instead of radical reactant CN, ${{\rm{H}}}_{2}\mathrm{CN}$ may also react with ${{\rm{C}}}_{2}{{\rm{H}}}_{5}$ to form propanimine directly by reaction R19. This reaction is assumed to be barrier-less in nature. We found that the first step (R21) of hydrogen addition with propionitrile has a barrier of 2712 K and the second step (R22) is a radical–radical interaction. We assume that the second step of this sequence is barrier-less. For the gas phase hydrogenation reaction (G21), our calculated ${\rm{\Delta }}G\ddagger$ parameter is found to be 11.03 Kcal/mol. In Figures 2(a), (b), and 3, we have shown the time evolution of propanimine (1Z-1-propanimine). It is evident from the figures that the production of (1Z)-1-propanimine is only favorable in the hot-core region. We have a peak gas phase abundance of (1Z)-1-propanimine (propanimine) of $2.20\times {10}^{-08}$ .

3.6. C₃H₉N Isomeric Group

We consider four species (Figure 14) from this isomeric group, namely, 2-aminopropane, propylamine, ethylmethylamine, and trimethylamine. Methylamine is the most stable isomer of the ${\mathrm{CH}}_{5}{\rm{N}}$ group, and ethylamine is the most stable isomer of the ${{\rm{C}}}_{2}{{\rm{H}}}_{7}{\rm{N}}$ isomeric group. In general, it is expected that the branched chain molecules would be comparatively more stable than the other species of an isomeric group. Recently, Etim et al. (2017) showed that isopropyl cyanide, a branched chain molecule, is the most stable within the ${{\rm{C}}}_{4}{{\rm{H}}}_{7}{\rm{N}}$ isomeric group and tert-butyl cyanide, another branched chain molecule, is the most stable species within the ${{\rm{C}}}_{5}{{\rm{H}}}_{9}{\rm{N}}$ isomeric group. Following the similar trend, we found that 2-aminopropane, a branched chain molecule of the ${{\rm{C}}}_{3}{{\rm{H}}}_{9}{\rm{N}}$ isomeric group, is the most stable isomer of this group. 2-aminopropane is found to be 2.51 Kcal/mol more stable than the propylamine. In Figure 15, we have shown the enthalpy of formation of these four species. Relative energy and enthalpy of formation of these four isomers are shown in Table 2 and arranged based on their enthalpy of formation. Theoretically calculated and experimentally obtained enthalpy of formation values have a similar trend. From Table 2, it is evident that the calculated enthalpies of formation with the B3LYP/6-31G(d,p) method appear to be comparatively closer to the experimental values than those of the G4 composite method. The expected intensity ratio with respect to the species having the minimum enthalpy of formation is shown in Figure 16. Interestingly, though trimethylamine has the lowest total dipole moment value among this isomeric group, the rotational intensity is found to be maximum because of its lower partition function. More interestingly, due to its unique structure, rotational constants A and B have the same value (8.75934 GHz). We also have reconfirmed this unique nature of trimethylamine (an oblate symmetric top species) by using the G4 composite method and the HF/6-31G(3df) method. Since the production of propanimine from the very last isomeric group of this sequence, ${{\rm{C}}}_{3}{{\rm{H}}}_{7}{\rm{N}}$ , is not significantly higher, we have not prepared any reaction pathways for the formation of any species from the ${{\rm{C}}}_{3}{{\rm{H}}}_{9}{\rm{N}}$ isomeric group.

**Figure 14.** ${{\rm{C}}}_{3}{{\rm{H}}}_{9}{\rm{N}}$ isomers.
Download figure:
Standard image High-resolution image

**Figure 15.** Enthalpy of formation of the ${{\rm{C}}}_{3}{{\rm{H}}}_{9}{\rm{N}}$ isomeric group.
Download figure:
Standard image High-resolution image

**Figure 16.** Expected intensity ratio of the ${{\rm{C}}}_{3}{{\rm{H}}}_{9}{\rm{N}}$ isomeric group by considering three components of the dipole moment and effective dipole moment of all the species.
Download figure:
Standard image High-resolution image

In this section, we have investigated the chemical abundances of some specific groups of amine and aldimines. Results presented here clearly show that imines (methanimine, ethanimine, and propanimine) and amines (methylamine and ethylamine) may be efficiently produced in the ice phase (either in the isothermal or in the hot-core regime). Depending on the barrier energy considered, Figure 3 depicts a nice trend of sublimation. For example, we have adopted a binding energy of ethylamine and methylamine of 6480 and 6584 K, respectively. Maintaining the trend, ethylamine starts to sublime faster than methylamine. Similarly, maintaining the trend of binding energies (5534, 5580, and 6337 K for methanimine, ethanimine, and propanimine, respectively) the sublimation sequence is also obtained for the imines.

4. Astrophysical Implications of This Work

Methanimine is an important prebiotic molecule that is believed to be the precursor molecule for the formation of the simplest amino acid, glycine. It was mentioned earlier that this species is detected in the ISM. Most interestingly, this species is also detected in the upper atmosphere of Titan (the massive moon of Saturn; Vuitton et al. 2006). The present atmosphere of Titan resembles the primeval atmosphere of Earth and thus is thought to be important for the abiotic synthesis. Our present study found that methanimine may be further processed to form methylamine, which is yet to be observed in Titan's atmosphere. Modeling Titan's atmosphere is beyond the scope of this paper. However, the inclusion of proposed pathways in the modeling of Titan's atmosphere may come up with the higher mixing ratios of higher-order imines and amines in Titan's atmosphere.

We have performed radiative transfer modeling (with both LTE and non-LTE consideration), which may be useful for the future astronomical observation of ethylamine and propanimine in the ISM. For the calculation of the line parameters using an LTE approximation, we use the CASSIS interactive spectrum analyzer (http://cassis.irap.omp.eu/). In Table 6, we have pointed out some of the most intense transitions of ethylamine that fall in ALMA bands 1–5. Required spectroscopic details for ethylamine are available at https://www.astro.uni-koeln.de/cdms/catalog. Similarly, in Table 7, intense transitions of propanimine are shown. Required spectroscopic details for (1Z)-1-propanimine are obtained by including the experimentally obtained rotational and distortional constants in the SPCAT program (Pickett 1991). For preparing these tables, we have used a column density of ${{\rm{H}}}_{2}={10}^{23}\,{\mathrm{cm}}^{-2},{n}_{{\rm{H}}}={10}^{7}$ cm⁻³, excitation temperature = 130 K, FWHM = 10 km s⁻¹, ${V}_{\mathrm{LSR}}=64$ km s⁻¹, source size $=3^{\prime\prime}$ , abundance of ethylamine = $4.0\times {10}^{-08}$ , and abundance of propanimine = $2\times {10}^{-8}$ .

We have also performed a non-LTE calculation by using the RADEX program (Van der Tak et al. 2007). A collisional data file for ethylamine and propanimine is yet to be available in any database. Thus, we prepare the collisional data file in the appropriate format from the spectral information available in JPL (for trans-ethylamine) and from our calculation (for (1Z)-1-propanimine) propanimine.tar.gz. Altogether we have considered transitions between 251 energy levels. Here, we assume that H₂ is the colliding partner. In order to estimate the line profile with non-LTE, here we have estimated the collisional rate of ethylamine and propanimine by following the relation mentioned in Sharma & Chandra (2001). Sharma & Chandra (2001) estimated the collisional rate coefficient for a downward transition of an asymmetric top molecule, cyclopropene at temperature "T," by

$\begin{eqnarray}&&C(J^{\prime\prime} {K}_{a}^{{\prime\prime} }{K}_{c}^{{\prime\prime} }\to J^{\prime} {K}_{a}^{{\prime} }{K}_{c}^{{\prime} })=[1\times {10}^{-11}/(2J^{\prime\prime} +1)]\sqrt{T/30}.\end{eqnarray} \tag{ 3 }$

In Tables 8 and 9, we have pointed out the most intense transitions of trans-ethylamine and (1Z)-1-propanimine, respectively, which are falling within ALMA bands 1–5. For the non-LTE calculations, we have used a column density of ethylamine of 10¹⁵ cm⁻² and a column density of propanimine of $5.0\,\times {10}^{14}$ cm⁻², ${n}_{{\rm{H}}}={10}^{7}$ cm⁻³, excitation temperature $=130\,{\rm{K}},\ \mathrm{FWHM}=10\,\mathrm{km}\,{{\rm{s}}}^{-1}$ .

For the transitions pointed out in Tables 8 and 9, we have studied the density variation of ethylamine (Figure 17) and propanimine (Figure 18) with the non-LTE consideration. Figures 17 and 18 would serve as a very useful starting point for the observation of ethylamine and propanimine in the ISM. It is to be noted that in the absence of the measured or calculated collisional data file, we have used our estimated collisional rate, but it is known that the non-LTE transitions are heavily dependent on collisional rates, and consideration of random rates may end up with some misleading results.

5. Conclusions

In this work, we examine the possibility of detecting various molecules that belong to six specific isomeric groups. We have used the chemical abundance, enthalpy of formation, optimized energy, and expected intensity ratio to shortlist some species that might be viable candidates for future astronomical detection in the ISM. According to our calculation, ethylamine remains the most suitable candidate for future astronomical detection in the ISM. (1Z)-1-Propanimine also may be a potential candidate. From our gas-grain chemical modeling, we see that the precursor molecules (methylamine and ethylamine) of glycine could efficiently be formed around the star-forming region. Moreover, radiative transfer modeling (LTE and non-LTE) has been employed for the detection of these species in the ISM.

M.S. gratefully acknowledges DST, the Government of India for providing financial assistance through DST-INSPIRE Fellowship [IF160109] scheme. A.D. acknowledges the ISRO respond (grant No. ISRO/RES/2/402/16-17) for financial support. A.D. would also like to acknowledge DST grant No. SB/S2/HEP-021/2013. B.B. acknowledges DST-INSPIRE Fellowship [IF170046] for providing partial financial assistance.

Software: Gaussian 09 (Frisch et al. 2013), SPCAT (Pickett 1991), CASSIS (http://cassis.cesr.fr), RADEX (Van der Tak et al. 2007).

: Appendix

Gas phase reaction pathways for the formation/destruction of some important amines and aldimines (Table 5) along with the line parameters for the observations of Trans-ethylamine and (1Z)-1-Propanimine under LTE (Tables 6 and 7) as well as non-LTE (Tables 8 and 9) approximation.

Table 5. Gas Phase Formation and Destruction Pathways

Reaction Number (Type)	Reaction	α	β	γ	Rate Coefficient @ 10 K
	Formation Pathways
G1(RR)	${\rm{N}}+{\mathrm{CH}}_{3}\to {\mathrm{CH}}_{2}\mathrm{NH}$	$1.00\times {10}^{-15}$	−3.0	0.0	$2.70\times {10}^{-11}$
G2(RR)	$\mathrm{NH}+{\mathrm{CH}}_{2}\to {\mathrm{CH}}_{2}\mathrm{NH}$	$1.00\times {10}^{-15}$	−3.0	0.0	$2.70\times {10}^{-11}$
G3(RR)	${\mathrm{NH}}_{2}+\mathrm{CH}\to {\mathrm{CH}}_{2}\mathrm{NH}$	$1.00\times {10}^{-15}$	−3.0	0.0	$2.70\times {10}^{-11}$
G4(NR)	${\rm{H}}+\mathrm{HCN}\to {{\rm{H}}}_{2}\mathrm{CN}$ ( ${\rm{\Delta }}G\ddagger=8.37$ ^a Kcal/mol)	⋯	⋯	⋯	⋯
G5(NR)	${\rm{H}}+\mathrm{HCN}\to \mathrm{HCNH}$ ( ${\rm{\Delta }}G\ddagger=10.06$ ^a Kcal/mol)	⋯	⋯	⋯	⋯
G6(RR)	${\rm{H}}+{{\rm{H}}}_{2}\mathrm{CN}\to {\mathrm{CH}}_{2}\mathrm{NH}$	$1.00\times {10}^{-15}$	−3.0	0.0	$2.70\times {10}^{-11}$
G7(RR)	${\rm{H}}+\mathrm{HCNH}\to {\mathrm{CH}}_{2}\mathrm{NH}$	$1.00\times {10}^{-15}$	−3.0	0.0	$2.70\times {10}^{-11}$
G8(NR)	${\rm{H}}+{\mathrm{CH}}_{2}\mathrm{NH}\to {\mathrm{CH}}_{3}\mathrm{NH}$ ( ${\rm{\Delta }}G\ddagger=7.84$ ^a Kcal/mol)	⋯	⋯	⋯	⋯
G9(NR)	${\rm{H}}+{\mathrm{CH}}_{2}\mathrm{NH}\to {\mathrm{CH}}_{2}{\mathrm{NH}}_{2}$ ( ${\rm{\Delta }}G\ddagger=11.64$ ^a Kcal/mol)	⋯	⋯	⋯	⋯
G10(RR)	${\rm{H}}+{\mathrm{CH}}_{3}\mathrm{NH}\to {\mathrm{CH}}_{3}{\mathrm{NH}}_{2}$	$1.00\times {10}^{-15}$	−3.0	0.0	$2.70\times {10}^{-11}$
G11(RR)	${\rm{H}}+{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}\to {\mathrm{CH}}_{3}{\mathrm{NH}}_{2}$	$1.00\times {10}^{-15}$	−3.0	0.0	$2.70\times {10}^{-11}$
G12(RR)	${\rm{H}}+{\mathrm{CH}}_{2}\mathrm{CN}\to {\mathrm{CH}}_{3}\mathrm{CN}$	$1.00\times {10}^{-15}$	−3.0	0.0	$2.70\times {10}^{-11}$
G13(RR)	${\mathrm{CH}}_{3}+\mathrm{CN}\to {\mathrm{CH}}_{3}\mathrm{CN}$	$1.00\times {10}^{-15}$	−3.0	0.0	$2.70\times {10}^{-11}$
G14(NR)	${\rm{H}}+{\mathrm{CH}}_{3}\mathrm{CN}\to {\mathrm{CH}}_{3}\mathrm{CNH}$ ( ${\rm{\Delta }}G\ddagger=10.32$ ^a Kcal/mol)	⋯	⋯	⋯	⋯
G15(RR)	${\rm{H}}+{\mathrm{CH}}_{3}\mathrm{CNH}\to {\mathrm{CH}}_{3}\mathrm{CHNH}$	$1.00\times {10}^{-15}$	−3.0	0.0	$2.70\times {10}^{-11}$
G16(RR)	${\mathrm{CH}}_{3}+{{\rm{H}}}_{2}\mathrm{CN}\to {\mathrm{CH}}_{3}\mathrm{CHNH}$	$1.00\times {10}^{-15}$	−3.0	0.0	$2.70\times {10}^{-11}$
G17(NR)	${\rm{H}}+{\mathrm{CH}}_{3}\mathrm{CHNH}\to {\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{NH}$ ( ${\rm{\Delta }}G\ddagger=9.98$ ^a Kcal/mol)	⋯	−3.0	0.0	⋯
G18(RR)	${\rm{H}}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{NH}\to {\mathrm{CH}}_{3}{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}$	$1.00\times {10}^{-15}$	−3.0	0.0	$2.70\times {10}^{-11}$
G19(RR)	${{\rm{C}}}_{2}{{\rm{H}}}_{5}+{{\rm{H}}}_{2}\mathrm{CN}\to {\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CHNH}$	$1.00\times {10}^{-15}$	−3.0	0.0	$2.70\times {10}^{-11}$
G20(RR)	${{\rm{C}}}_{2}{{\rm{H}}}_{5}+\mathrm{CN}\to {\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CN}$	$1.00\times {10}^{-15}$	−3.0	0.0	$2.70\times {10}^{-11}$
G21(NR)	${\rm{H}}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CN}\to {\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CNH}$ ( ${\rm{\Delta }}G\ddagger=11.03$ ^a Kcal/mol)	⋯	−3.0	0.0	⋯
G22(RR)	${\rm{H}}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CNH}\to {\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CHNH}$	$1.00\times {10}^{-15}$	−3.0	0.0	$2.70\times {10}^{-11}$
G23(RR)	${{\rm{C}}}_{2}{{\rm{H}}}_{5}+\mathrm{NH}\to {\mathrm{CH}}_{3}\mathrm{CHNH}+{\rm{H}}$	$2.75\times {10}^{-12}$	0.0	0.0	$2.75\times {10}^{-12}$
	Destruction Pathways
G24(IN)	${{\rm{C}}}^{+}+{\mathrm{CH}}_{3}\mathrm{CNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{3}^{+}+\mathrm{HNC}$	$8.10\times {10}^{-10}$	−0.5	0.0	$4.44\times {10}^{-9}$
G25(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}\mathrm{CNH}\to {\rm{C}}2{{\rm{H}}}_{4}{{\rm{N}}}^{+}+{\rm{H}}$	$2.50\times {10}^{-9}$	−0.5	0.0	$1.37\times {10}^{-8}$
G26(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}\mathrm{CNH}\to {\mathrm{CH}}_{3}{\mathrm{CN}}^{+}+{{\rm{H}}}_{2}$	$2.50\times {10}^{-9}$	−0.5	0.0	$1.37\times {10}^{-8}$
G27(IN)	${\mathrm{He}}^{+}+{\mathrm{CH}}_{3}\mathrm{CNH}\to \mathrm{He}+{\mathrm{HNC}}^{+}+{\mathrm{CH}}_{3}$	$1.80\times {10}^{-9}$	−0.5	0.0	$9.86\times {10}^{-9}$
G28(IN)	${\mathrm{He}}^{+}+{\mathrm{CH}}_{3}\mathrm{CNH}\to \mathrm{He}+\mathrm{HNC}+{\mathrm{CH}}_{3}^{+}$	$1.80\times {10}^{-9}$	−0.5	0.0	$9.86\times {10}^{-9}$
G29(IN)	${{\rm{H}}}_{3}^{+}+{\mathrm{CH}}_{3}\mathrm{CNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{5}{{\rm{N}}}^{+}+{{\rm{H}}}_{2}$	$1.50\times {10}^{-9}$	−0.5	0.0	$8.22\times {10}^{-9}$
G30(IN)	${{\rm{H}}}_{3}{{\rm{O}}}^{+}+{\mathrm{CH}}_{3}\mathrm{CNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{5}{{\rm{N}}}^{+}+{{\rm{H}}}_{2}{\rm{O}}$	$6.80\times {10}^{-10}$	−0.5	0.0	$3.72\times {10}^{-9}$
G31(IN)	${\mathrm{HCO}}^{+}+{\mathrm{CH}}_{3}\mathrm{CNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{5}{{\rm{N}}}^{+}+\mathrm{CO}$	$6.00\times {10}^{-10}$	−0.5	0.0	$3.29\times {10}^{-9}$
G32(IN)	${\mathrm{HCO}}_{2}^{+}+{\mathrm{CH}}_{3}\mathrm{CNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{5}{{\rm{N}}}^{+}+{\mathrm{CO}}_{2}$	$5.30\times {10}^{-10}$	−0.5	0.0	$2.90\times {10}^{-9}$
G33(IN)	${{\rm{C}}}^{+}+{\mathrm{CH}}_{3}\mathrm{CHNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{4}^{+}+\mathrm{HNC}$	$1.70\times {10}^{-9}$	−0.5	0.0	$9.31\times {10}^{-9}$
G34(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}\mathrm{CHNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{4}{{\rm{N}}}^{+}+{{\rm{H}}}_{2}$	$5.10\times {10}^{-9}$	−0.5	0.0	$2.79\times {10}^{-8}$
G35(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}\mathrm{CHNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{5}{{\rm{N}}}^{+}+{\rm{H}}$	$5.10\times {10}^{-9}$	−0.5	0.0	$2.79\times {10}^{-8}$
G36(IN)	${{\rm{H}}}_{3}^{+}+{\mathrm{CH}}_{3}\mathrm{CHNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{{\rm{H}}}_{2}$	$3.00\times {10}^{-9}$	−0.5	0.0	$1.64\times {10}^{-8}$
G37(IN)	${{\rm{H}}}_{3}{{\rm{O}}}^{+}+{\mathrm{CH}}_{3}\mathrm{CHNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{{\rm{H}}}_{2}O$	$1.40\times {10}^{-9}$	−0.5	0.0	$7.67\times {10}^{-9}$
G38(IN)	${\mathrm{HCO}}^{+}+{\mathrm{CH}}_{3}\mathrm{CHNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+\mathrm{CO}$	$1.20\times {10}^{-9}$	−0.5	0.0	$6.57\times {10}^{-9}$
G39(IN)	${\mathrm{HCO}}_{2}^{+}+{\mathrm{CH}}_{3}\mathrm{CHNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{\mathrm{CO}}_{2}$	$1.10\times {10}^{-9}$	−0.5	0.0	$6.02\times {10}^{-9}$
G40(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}\to {\mathrm{NH}}_{2}+{\mathrm{CH}}_{3}^{+}$	$1.00\times {10}^{-9}$	0.0	0.0	$1.00\times {10}^{-9}$
G41(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}\to {\mathrm{NH}}_{2}^{+}+{\mathrm{CH}}_{3}$	$1.00\times {10}^{-9}$	0.0	0.0	$1.00\times {10}^{-9}$
G42(IN)	${{\rm{H}}}_{3}{O}^{+}+{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}\to {\mathrm{CH}}_{2}{\mathrm{NH}}_{3}^{+}+{{\rm{H}}}_{2}{\rm{O}}$	$1.00\times {10}^{-9}$	0.0	0.0	$1.00\times {10}^{-9}$
G43(IN)	${\mathrm{HCO}}^{+}+{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}\to {\mathrm{CH}}_{2}{\mathrm{NH}}_{3}^{+}+\mathrm{CO}$	$1.00\times {10}^{-9}$	0.0	0.0	$1.00\times {10}^{-9}$
G44(IN)	${\mathrm{He}}^{+}+{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}\to \mathrm{NH}+{\mathrm{CH}}_{3}^{+}+\mathrm{He}$	$1.00\times {10}^{-9}$	0.0	0.0	$1.00\times {10}^{-9}$
G45(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}\mathrm{NH}\to {\mathrm{NH}}_{2}^{+}+{\mathrm{CH}}_{3}$	$1.00\times {10}^{-9}$	0.0	0.0	$1.00\times {10}^{-9}$
G46(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}\mathrm{NH}\to {\mathrm{NH}}_{2}+{\mathrm{CH}}_{3}^{+}$	$1.00\times {10}^{-9}$	0.0	0.0	$1.00\times {10}^{-9}$
G47(IN)	${{\rm{H}}}_{3}{{\rm{O}}}^{+}+{\mathrm{CH}}_{3}\mathrm{NH}\to {\mathrm{CH}}_{2}{\mathrm{NH}}_{3}^{+}+{{\rm{H}}}_{2}{\rm{O}}$	$1.00\times {10}^{-9}$	0.0	0.0	$1.00\times {10}^{-9}$
G48(IN)	${\mathrm{HCO}}^{+}+{\mathrm{CH}}_{3}\mathrm{NH}\to {\mathrm{CH}}_{2}{\mathrm{NH}}_{3}^{+}+\mathrm{CO}$	$1.00\times {10}^{-9}$	0.0	0.0	$1.00\times {10}^{-9}$
G49(IN)	${\mathrm{He}}^{+}+{\mathrm{CH}}_{3}\mathrm{NH}\to \mathrm{NH}+{\mathrm{CH}}_{3}^{+}+\mathrm{He}$	$1.00\times {10}^{-9}$	0.0	0.0	$1.00\times {10}^{-9}$
G50(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{NH}}_{2}\to {\mathrm{NH}}_{2}+{\mathrm{CH}}_{4}^{+}$	$1.00\times {10}^{-9}$	0.0	0.0	$1.00\times {10}^{-9}$
G51(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{NH}}_{2}\to {\mathrm{NH}}_{2}^{+}+{\mathrm{CH}}_{4}$	$1.00\times {10}^{-9}$	0.0	0.0	$1.00\times {10}^{-9}$
G52(IN)	${{\rm{H}}}_{3}{{\rm{O}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{NH}}_{2}\to {\mathrm{CH}}_{3}{\mathrm{NH}}_{3}^{+}+{{\rm{H}}}_{2}{\rm{O}}$	$1.00\times {10}^{-9}$	0.0	0.0	$1.00\times {10}^{-9}$
G53(IN)	${\mathrm{HCO}}^{+}+{\mathrm{CH}}_{3}{\mathrm{NH}}_{2}\to {\mathrm{CH}}_{3}{\mathrm{NH}}_{3}^{+}+\mathrm{CO}$	$1.00\times {10}^{-9}$	0.0	0.0	$1.00\times {10}^{-9}$
G54(IN)	${\mathrm{He}}^{+}+{\mathrm{CH}}_{3}{\mathrm{NH}}_{2}\to {\mathrm{NH}}_{2}+{\mathrm{CH}}_{3}^{+}+\mathrm{He}$	$1.00\times {10}^{-9}$	0.0	0.0	$1.00\times {10}^{-9}$
G55(IN)	${{\rm{C}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}\to {{\rm{C}}}_{2}{{\rm{H}}}_{5}^{+}+{{\rm{H}}}_{2}\mathrm{CN}$	$1.70\times {10}^{-9}$	−0.5	0.0	$9.31\times {10}^{-9}$
G56(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}\to {\mathrm{CH}}_{3}{\mathrm{CNH}}^{+}+{{\rm{H}}}_{2}+{{\rm{H}}}_{2}$	$5.10\times {10}^{-9}$	−0.5	0.0	$2.79\times {10}^{-8}$
G57(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}\to {{\rm{C}}}_{2}{{\rm{H}}}_{4}{{\rm{N}}}^{+}+{{\rm{H}}}_{2}+{{\rm{H}}}_{2}$	$5.10\times {10}^{-9}$	−0.5	0.0	$2.79\times {10}^{-8}$
G58(IN)	${{\rm{H}}}_{3}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{{\rm{H}}}_{2}+{{\rm{H}}}_{2}$	$3.00\times {10}^{-9}$	−0.5	0.0	$1.64\times {10}^{-8}$
G59(IN)	${{\rm{H}}}_{3}{{\rm{O}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{{\rm{H}}}_{2}{\rm{O}}+{{\rm{H}}}_{2}$	$1.40\times {10}^{-9}$	−0.5	0.0	$7.67\times {10}^{-9}$
G60(IN)	${\mathrm{HCO}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+\mathrm{CO}+{{\rm{H}}}_{2}$	$1.20\times {10}^{-9}$	−0.5	0.0	$6.57\times {10}^{-9}$
G61(IN)	${\mathrm{HCO}}_{2}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{\mathrm{CO}}_{2}+{{\rm{H}}}_{2}$	$1.10\times {10}^{-9}$	−0.5	0.0	$6.02\times {10}^{-9}$
G62(IN)	${{\rm{C}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CN}\to {{\rm{C}}}_{2}{{\rm{H}}}_{5}^{+}+{{\rm{C}}}_{2}{\rm{N}}$	$1.70\times {10}^{-9}$	−0.5	0.0	$9.31\times {10}^{-9}$
G63(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CN}\to {\mathrm{CH}}_{3}{\mathrm{CNH}}^{+}+{\mathrm{CH}}_{2}$	$5.10\times {10}^{-9}$	−0.5	0.0	$2.79\times {10}^{-8}$
G64(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CN}\to {{\rm{C}}}_{2}{{\rm{H}}}_{4}{{\rm{N}}}^{+}+{\mathrm{CH}}_{2}$	$5.10\times {10}^{-9}$	−0.5	0.0	$2.79\times {10}^{-8}$
G65(IN)	${{\rm{H}}}_{3}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CN}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{\mathrm{CH}}_{2}$	$3.00\times {10}^{-9}$	−0.5	0.0	$1.64\times {10}^{-8}$
G66(IN)	${{\rm{H}}}_{3}{{\rm{O}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CN}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{{\rm{H}}}_{2}\mathrm{CO}$	$1.40\times {10}^{-9}$	−0.5	0.0	$7.67\times {10}^{-9}$
G67(IN)	${\mathrm{HCO}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CN}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{{\rm{C}}}_{2}{\rm{O}}$	$1.20\times {10}^{-9}$	−0.5	0.0	$6.57\times {10}^{-9}$
G68(IN)	${\mathrm{HCO}}_{2}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CN}\to {{\rm{C}}}_{2}{{\rm{H}}}_{5}^{+}+{\mathrm{CO}}_{2}+\mathrm{HCN}$	$1.10\times {10}^{-9}$	−0.5	0.0	$6.02\times {10}^{-9}$
G69(IN)	${{\rm{C}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{5}^{+}+{{\rm{C}}}_{2}{\rm{N}}+{\rm{H}}$	$1.70\times {10}^{-9}$	−0.5	0.0	$9.31\times {10}^{-9}$
G70(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CNH}\to {\mathrm{CH}}_{3}{\mathrm{CNH}}^{+}+{\mathrm{CH}}_{2}+{\rm{H}}$	$5.10\times {10}^{-9}$	−0.5	0.0	$2.79\times {10}^{-8}$
G71(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{4}{{\rm{N}}}^{+}+{\mathrm{CH}}_{3}$	$5.10\times {10}^{-9}$	−0.5	0.0	$2.79\times {10}^{-8}$
G72(IN)	${{\rm{H}}}_{3}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{\mathrm{CH}}_{3}$	$3.00\times {10}^{-9}$	−0.5	0.0	$1.64\times {10}^{-8}$
G73(IN)	${{\rm{H}}}_{3}{{\rm{O}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{{\rm{H}}}_{2}\mathrm{CO}+{\rm{H}}$	$1.40\times {10}^{-9}$	−0.5	0.0	$7.67\times {10}^{-9}$
G74(IN)	${\mathrm{HCO}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{{\rm{C}}}_{2}{\rm{O}}+{\rm{H}}$	$1.20\times {10}^{-9}$	−0.5	0.0	$6.57\times {10}^{-9}$
G75(IN)	${\mathrm{HCO}}_{2}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{{\rm{C}}}_{2}{\rm{O}}+\mathrm{OH}$	$1.10\times {10}^{-9}$	−0.5	0.0	$6.02\times {10}^{-9}$
G76(IN)	${{\rm{C}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CHNH}\to {C}_{2}{{\rm{H}}}_{5}^{+}+{{\rm{C}}}_{2}{\rm{N}}+{{\rm{H}}}_{2}$	$1.70\times {10}^{-9}$	−0.5	0.0	$9.31\times {10}^{-9}$
G77(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CHNH}\to {\mathrm{CH}}_{3}{\mathrm{CNH}}^{+}+{\mathrm{CH}}_{3}+{\rm{H}}$	$5.10\times {10}^{-9}$	−0.5	0.0	$2.79\times {10}^{-8}$
G78(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CHNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{4}{{\rm{N}}}^{+}+{\mathrm{CH}}_{3}+{\rm{H}}$	$5.10\times {10}^{-9}$	−0.5	0.0	$2.79\times {10}^{-8}$
G79(IN)	${{\rm{H}}}_{3}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CHNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{\mathrm{CH}}_{3}+{\rm{H}}$	$3.00\times {10}^{-9}$	−0.5	0.0	$1.64\times {10}^{-8}$
G80(IN)	${{\rm{H}}}_{3}{{\rm{O}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CHNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{{\rm{H}}}_{2}\mathrm{CO}+{{\rm{H}}}_{2}$	$1.40\times {10}^{-9}$	−0.5	0.0	$7.67\times {10}^{-9}$
G81(IN)	${\mathrm{HCO}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CHNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{{\rm{C}}}_{2}{\rm{O}}+{{\rm{H}}}_{2}$	$1.20\times {10}^{-9}$	−0.5	0.0	$6.57\times {10}^{-9}$
G82(IN)	${\mathrm{HCO}}_{2}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CHNH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{{\rm{C}}}_{2}{\rm{O}}+{{\rm{H}}}_{2}{\rm{O}}$	$1.10\times {10}^{-9}$	−0.5	0.0	$6.02\times {10}^{-9}$
G83(IN)	${{\rm{C}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{NH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{5}^{+}+\mathrm{HCN}$	$1.70\times {10}^{-9}$	−0.5	0.0	$9.31\times {10}^{-9}$
G84(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{NH}\to {\mathrm{CH}}_{3}{\mathrm{CNH}}^{+}+{{\rm{H}}}_{2}+{\rm{H}}$	$5.10\times {10}^{-9}$	−0.5	0.0	$2.79\times {10}^{-8}$
G85(IN)	${{\rm{H}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{NH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{4}{{\rm{N}}}^{+}+{{\rm{H}}}_{2}+{\rm{H}}$	$5.10\times {10}^{-9}$	−0.5	0.0	$2.79\times {10}^{-8}$
G86(IN)	${{\rm{H}}}_{3}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{NH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{{\rm{H}}}_{2}+{\rm{H}}$	$3.00\times {10}^{-9}$	−0.5	0.0	$1.64\times {10}^{-8}$
G87(IN)	${{\rm{H}}}_{3}{{\rm{O}}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{NH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{{\rm{H}}}_{2}{\rm{O}}+{\rm{H}}$	$1.40\times {10}^{-9}$	−0.5	0.0	$7.67\times {10}^{-9}$
G88(IN)	${\mathrm{HCO}}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{NH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+\mathrm{CO}+{\rm{H}}$	$1.20\times {10}^{-9}$	−0.5	0.0	$6.57\times {10}^{-9}$
G89(IN)	${\mathrm{HCO}}_{2}^{+}+{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{NH}\to {{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{\mathrm{CO}}_{2}+{\rm{H}}$	$1.10\times {10}^{-9}$	−0.5	0.0	$6.02\times {10}^{-9}$
G90(NN)	${\mathrm{CH}}_{3}\mathrm{CNH}+{\rm{H}}\to {\mathrm{CH}}_{3}\mathrm{CN}+{{\rm{H}}}_{2}$	$1.28\times {10}^{-11}$	0.5	0.0	$2.37\times {10}^{-12}$
G91(NN)	${\mathrm{CH}}_{3}\mathrm{CHNH}+{\rm{H}}\to {\mathrm{CH}}_{3}\mathrm{CNH}+{{\rm{H}}}_{2}$	$1.28\times {10}^{-11}$	0.5	1050.0	$2.37\times {10}^{-12}$
G92(NN)	${\mathrm{CH}}_{3}\mathrm{CNH}+{\rm{C}}\to {\mathrm{CH}}_{3}\mathrm{CN}+\mathrm{CH}$	$4.18\times {10}^{-12}$	0.5	0.0	$7.67\times {10}^{-13}$
G93(NN)	${\mathrm{CH}}_{3}\mathrm{CHNH}+{\rm{C}}\to {\mathrm{CH}}_{3}\mathrm{CNH}+\mathrm{CH}$	$4.18\times {10}^{-12}$	0.5	0.0	$7.67\times {10}^{-13}$
G94(NN)	${{\rm{C}}}_{2}{{\rm{H}}}_{5}+{\rm{N}}\to {\mathrm{CH}}_{3}\mathrm{CNH}+{\rm{H}}$	$8.30\times {10}^{-12}$	0.0	0.0	$8.30\times {10}^{-12}$
G95(DR)	${{\rm{C}}}_{2}{{\rm{H}}}_{4}{{\rm{N}}}^{+}+{{\rm{e}}}^{-}\to {\mathrm{CH}}_{3}\mathrm{CN}+{\rm{H}}$	$1.50\times {10}^{-7}$	−0.5	0.0	$8.22\times {10}^{-7}$
G96(DR)	${{\rm{C}}}_{2}{{\rm{H}}}_{4}{{\rm{N}}}^{+}+{{\rm{e}}}^{-}\to {\mathrm{CH}}_{2}\mathrm{CN}+{\rm{H}}+{\rm{H}}$	$1.50\times {10}^{-7}$	−0.5	0.0	$8.22\times {10}^{-7}$
G97(DR)	${{\rm{C}}}_{2}{{\rm{H}}}_{5}{{\rm{N}}}^{+}+{{\rm{e}}}^{-}\to {\mathrm{CH}}_{3}\mathrm{CNH}+{\rm{H}}$	$1.50\times {10}^{-7}$	−0.5	0.0	$8.22\times {10}^{-7}$
G98(DR)	${{\rm{C}}}_{2}{{\rm{H}}}_{5}{{\rm{N}}}^{+}+{{\rm{e}}}^{-}\to {\mathrm{CH}}_{3}+{{\rm{H}}}_{2}\mathrm{CN}$	$1.50\times {10}^{-7}$	−0.5	0.0	$8.22\times {10}^{-7}$
G99(DR)	${{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{e}^{-}\to {\mathrm{CH}}_{3}\mathrm{CHNH}+{\rm{H}}$	$1.50\times {10}^{-7}$	−0.5	0.0	$8.22\times {10}^{-7}$
G100(DR)	${{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{N}}}^{+}+{{\rm{e}}}^{-}\to {\mathrm{CH}}_{4}+{{\rm{H}}}_{2}\mathrm{CN}$	$1.50\times {10}^{-7}$	−0.5	0.0	$8.22\times {10}^{-7}$
G101(DR)	${\mathrm{CH}}_{2}{\mathrm{NH}}_{3}^{+}+{{\rm{e}}}^{-}\to {\mathrm{CH}}_{4}+\mathrm{NH}$	$1.50\times {10}^{-7}$	−0.5	0.0	$8.22\times {10}^{-7}$
G102(DR)	${\mathrm{CH}}_{3}{\mathrm{NH}}_{3}^{+}+{{\rm{e}}}^{-}\to {\mathrm{CH}}_{4}+{\mathrm{NH}}_{2}$	$1.50\times {10}^{-7}$	−0.5	0.0	$8.22\times {10}^{-7}$
G103(PH)	${\mathrm{CH}}_{3}\mathrm{CNH}+\mathrm{PHOTON}\to {\mathrm{CH}}_{3}+\mathrm{HNC}$	$1.00\times {10}^{-9}$	0.0	1.9	$5.60\times {10}^{-18}$
G104(PH)	${\mathrm{CH}}_{3}\mathrm{CNH}+\mathrm{PHOTON}\to {\mathrm{CH}}_{3}\mathrm{CN}+{\rm{H}}$	$1.00\times {10}^{-9}$	0.0	1.9	$5.60\times {10}^{-18}$
G105(PH)	${\mathrm{CH}}_{3}\mathrm{CHNH}+\mathrm{PHOTON}\to {\mathrm{CH}}_{3}+{{\rm{H}}}_{2}\mathrm{CN}$	$1.00\times {10}^{-9}$	0.0	1.9	$5.60\times {10}^{-18}$
G106(PH)	${\mathrm{CH}}_{3}\mathrm{CHNH}+\mathrm{PHOTON}\to {\mathrm{CH}}_{3}\mathrm{CNH}+{\rm{H}}$	$1.00\times {10}^{-9}$	0.0	1.9	$5.60\times {10}^{-18}$
G107(PH)	${\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CN}+\mathrm{PHOTON}\to {\mathrm{CH}}_{3}\mathrm{CNH}+\mathrm{CH}$	$1.00\times {10}^{-9}$	0.0	1.9	$5.60\times {10}^{-18}$
G108(PH)	${\mathrm{CH}}_{3}{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}+\mathrm{PHOTON}\to {\mathrm{CH}}_{3}{\mathrm{NH}}_{2}+{\mathrm{CH}}_{2}$	$1.00\times {10}^{-9}$	0.0	1.9	$5.60\times {10}^{-18}$
G109(PH)	${\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CNH}+\mathrm{PHOTON}\to {\mathrm{CH}}_{3}\mathrm{CNH}+{\mathrm{CH}}_{2}$	$1.00\times {10}^{-9}$	0.0	1.9	$5.60\times {10}^{-18}$
G110(PH)	${\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CHNH}+\mathrm{PHOTON}\to {\mathrm{CH}}_{3}\mathrm{CNH}+{\mathrm{CH}}_{3}$	$1.00\times {10}^{-9}$	0.0	1.9	$5.60\times {10}^{-18}$
G111(PH)	${\mathrm{CH}}_{2}{\mathrm{NH}}_{2}+\mathrm{PHOTON}\to {{\rm{H}}}_{2}\mathrm{CN}+{{\rm{H}}}_{2}$	$1.00\times {10}^{-9}$	0.0	1.6	$3.94\times {10}^{-16}$
G112(PH)	${\mathrm{CH}}_{3}\mathrm{NH}+\mathrm{PHOTON}\to {{\rm{H}}}_{2}\mathrm{CN}+{{\rm{H}}}_{2}$	$1.00\times {10}^{-9}$	0.0	1.6	$3.94\times {10}^{-16}$
G113(PH)	${\mathrm{CH}}_{3}{\mathrm{NH}}_{2}+\mathrm{PHOTON}\to {{\rm{H}}}_{2}\mathrm{CN}+{{\rm{H}}}_{2}+{\rm{H}}$	$3.50\times {10}^{-9}$	0.0	1.6	$3.94\times {10}^{-16}$
G114(PH)	${\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{NH}+\mathrm{PHOTON}\to {\mathrm{CH}}_{3}\mathrm{CHNH}+{\rm{H}}$	$3.50\times {10}^{-9}$	0.0	1.6	$3.94\times {10}^{-16}$
G115(PH)	${\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{NH}+\mathrm{PHOTON}\to {{\rm{C}}}_{2}{{\rm{H}}}_{5}+\mathrm{NH}$	$3.50\times {10}^{-9}$	0.0	1.6	$3.94\times {10}^{-16}$
G116(CR)	${\mathrm{CH}}_{3}\mathrm{CNH}+\mathrm{CRPHOT}\to {\mathrm{CH}}_{3}+\mathrm{HNC}$	$1.30\times {10}^{-17}$	0.0	1.9	$1.95\times {10}^{-14}$
G117(CR)	${\mathrm{CH}}_{3}\mathrm{CNH}+\mathrm{CRPHOT}\to {\mathrm{CH}}_{3}\mathrm{CN}+{\rm{H}}$	$1.30\times {10}^{-17}$	0.0	1.9	$1.95\times {10}^{-14}$
G118(CR)	${\mathrm{CH}}_{3}\mathrm{CHNH}+\mathrm{CRPHOT}\to {\mathrm{CH}}_{3}+{{\rm{H}}}_{2}\mathrm{CN}$	$1.30\times {10}^{-17}$	0.0	1.9	$1.95\times {10}^{-14}$
G119(CR)	${\mathrm{CH}}_{3}\mathrm{CHNH}+\mathrm{CRPHOT}\to {\mathrm{CH}}_{3}\mathrm{CNH}+{\rm{H}}$	$1.30\times {10}^{-17}$	0.0	1.9	$1.95\times {10}^{-14}$
G120(CR)	${\mathrm{CH}}_{3}{\mathrm{CH}}_{2}{\mathrm{NH}}_{2}+\mathrm{CRPHOT}\to {\mathrm{CH}}_{3}{\mathrm{NH}}_{2}+{\mathrm{CH}}_{2}$	$1.30\times {10}^{-17}$	0.0	1.9	$1.95\times {10}^{-14}$
G121(CR)	${\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CN}+\mathrm{CRPHOT}\to {\mathrm{CH}}_{3}\mathrm{CNH}+\mathrm{CH}$	$1.30\times {10}^{-17}$	0.0	1.9	$1.95\times {10}^{-14}$
G122(CR)	${\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CNH}+\mathrm{CRPHOT}\to {\mathrm{CH}}_{3}\mathrm{CNH}+{\mathrm{CH}}_{2}$	$1.30\times {10}^{-17}$	0.0	1.9	$1.95\times {10}^{-14}$
G123(CR)	${\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{CHNH}+\mathrm{CRPHOT}\to {\mathrm{CH}}_{3}\mathrm{CNH}+{\mathrm{CH}}_{3}$	$1.30\times {10}^{-17}$	0.0	1.9	$1.95\times {10}^{-14}$
G124(CR)	${\mathrm{CH}}_{2}{\mathrm{NH}}_{2}+\mathrm{CRPHOT}\to \mathrm{NH}+{\mathrm{CH}}_{3}$	$1.30\times {10}^{-17}$	0.0	500.0	$1.95\times {10}^{-14}$
G125(CR)	${\mathrm{CH}}_{3}\mathrm{NH}+\mathrm{CRPHOT}\to \mathrm{NH}+{\mathrm{CH}}_{3}$	$1.30\times {10}^{-17}$	0.0	500.0	$1.95\times {10}^{-14}$
G126(CR)	${\mathrm{CH}}_{3}{\mathrm{NH}}_{2}+\mathrm{CRPHOT}\to {\mathrm{NH}}_{2}+{\mathrm{CH}}_{3}$	$1.30\times {10}^{-17}$	0.0	500.0	$1.95\times {10}^{-14}$
G127(CR)	${\mathrm{CH}}_{3}\mathrm{CH}2\mathrm{NH}+\mathrm{CRPHOT}\to {\mathrm{CH}}_{3}\mathrm{CHNH}+{\rm{H}}$	$1.30\times {10}^{-17}$	0.0	1.9	$1.95\times {10}^{-14}$
G128(CR)	${\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{NH}+\mathrm{CRPHOT}\to {{\rm{C}}}_{2}{{\rm{H}}}_{5}+\mathrm{NH}$	$1.30\times {10}^{-17}$	0.0	1.9	$1.95\times {10}^{-14}$

Note.

^aThis work.

Download table as: ASCIITypeset images: 1 2 3

Table 6. Line Parameters of Trans-ethylamine in the Millimeter and Submillimeter Regime Using ALMA (LTE)

Frequency Range (GHz)	Frequency (GHz)^a	Transition (J' ${k}_{a}^{{\prime} }$ ${k}_{c}^{{\prime} }$ v'– ${J}^{{\prime\prime} }$ ${k}_{a}^{{\prime\prime} }$ ${k}_{c}^{{\prime\prime} }$ ${v}^{{\prime\prime} }$ )	Intensity (K)
	31.4005744	5 1 4 0–5 0 5 0	0.0058
	33.0673762	2 0 2 1–1 0 1 1	0.0063
31–45 (ALMA band 1)	34.9850027	6 1 5 0–6 0 6 0	0.008
	39.4293083	7 1 6 0–7 0 7 0	0.011
	44.8063428	8 1 7 0–8 0 8 0	0.015

	80.241995	5 1 5 1–4 1 4 1	0.098
	82.168784	5 0 5 1–4 0 4 1	0.106
67–90 (ALMA band 2)	82.674301	5 2 4 1–4 2 3 1	0.088
and	83.24287	5 2 3 1–4 2 2 1	0.089
84–116 (ALMA band 3)	84.980785	5 1 4 1–4 1 3 1	0.107
	101.886754	6 1 5 1–5 1 4 1	0.169
	112.158369	7 1 7 1–6 1 6 1	0.222
	114.294235	7 0 7 1–6 0 6 1	0.234
	115.604884	7 2 6 1–6 2 5 1	0.211
	115.9771874	7 4 3 1–6 4 2 1	0.256

	145.871741	9 0 9 1–8 0 8 1	0.38
	149.11269	9 5 5 1–8 5 4 1 (9 5 4 1–8 5 3 1)	0.436
125–163 (ALMA band 4)	152.224777	9 1 8 1–8 1 7 1	0.391
	159.753196	10 1 10 1–9 1 9 1	0.445
	161.496431	10 0 10 1–9 0 9 1	0.45

	182.3234429	11 5 7 0–10 5 6 0	0.684
	198.94447	12 5 8 1–11 5 7 1	0.767
163–211 (ALMA band 5)	198.945801	12 5 7 1–11 5 6 1	0.768
	207.02715	13 1 13 1–12 1 12 1	0.64
	208.053547	13 0 13 1–12 0 12 1	0.65

Note.

^aFor the transitions with the same J' ${k}_{a}^{{\prime} }$ ${k}_{a}^{{\prime} }$ ${k}_{c}^{{\prime} }$ ${k}_{c}^{{\prime} }$ – ${J}^{{\prime\prime} }$ ${J}^{{\prime\prime} }$ ${k}_{a}^{{\prime\prime} }$ ${k}_{a}^{{\prime\prime} }$ ${k}_{c}^{{\prime\prime} }$ ${k}_{c}^{{\prime\prime} }$ but having different vibrational state, please see the cat file available at https://www.astro.uni-koeln.de/cdms/catalog.

Download table as: ASCII Typeset image

Table 7. Line Parameters of (1Z)-1-Propanimine in the Millimeter and Submillimeter Regime Using ALMA (LTE)

Frequency Range (GHz)	Frequency (GHz)^a	Transition (J' ${k}_{a}^{{\prime} }$ ${k}_{c}^{{\prime} }$ v'– ${J}^{{\prime\prime} }$ ${k}_{a}^{{\prime\prime} }$ ${k}_{c}^{{\prime\prime} }$ ${v}^{{\prime\prime} }$ )	Intensity (K)
	33.5198821	4 1 4 3–3 1 3 2	0.117
	33.7888724	4 0 4 5–3 0 3 4	0.136
	33.7897526	4 2 3 4–3 2 2 3	0.105
	34.0663468	4 1 3 4v3 1 2 3	0.123
31–45 (ALMA band 1)	41.897946	5 1 5 6–4 1 4 5	0.261
	42.2302861	5 0 5 6–4 0 4 5	0.290
	42.2318919	5 3 3 5–4 3 1 5	0.326
	42.2361126	5 2 4 6–4 2 3 5	0.227
	42.5812455	5 1 4 6–4 1 3 5	0.270

	67.0236193	8 1 8 8–7 1 7 7	1.110
	67.5282969	8 0 8 8–7 0 7 7	2.252
	67.5717125	8 3 6 7–7 3 5 8	1.725
	68.117366	8 1 7 8–7 1 6 7	1.145
	75.3952267	9 1 9 9–8 1 8 8	1.510
	75.9707109	9 5 4 8–8 5 3 7	1.720
	75.9497207	9 0 9 10–8 2 6 9	1.440
67–90 (ALMA band 2)	76.0013965	9 4 6 10–8 4 49	2.252
and	76.0187663	9 3 6 9–8 3 5 9	2.244
84–116 (ALMA band 3)	76.6257696	9 1 8 9–8 1 7 8	1.555
	83.7646502	10 11 0 10–9 1 9 9	1.955
	84.364287	10 0 10 9–9 1 8 9	2.000
	84.4134387	10 5 6 11–9 5 4 10	2.40
	84.4483753	10 4 6 9–9 4 5 10	4.650
	84.4661717	10 3 7 10–9 3 6 10	2.450
	84.5650434	10 2 8 10–9 2 7 9	1.870
	85.1318785	10 0 10 9–9 1 8 9	2.080
	92.1316784	11 1 11 11–10 1 10 10	2.420
	92.7713594	11 0 11 12–10 0 10 11	2.480
	92.8567065	11 5 6 10–10 5 6 9	3.150
	92.8959487	11 4 8 10–10 4 6 9	3.720
	93.0411029	11 2 9 11–10 2 8 10	3.720
	93.6354011	11 1 10 12–10 1 9 11	2.480
	100.4962033	12 1 12 11–11 1 11 12	2.900
	101.1702803	12 0 12 12–11 0 11 11	2.977
	101.3005235	12 5 8 13–11 5 6 12	3.925
	101.3444369	12 4 8 12–12 4 7 11	4.550
	101.5225577	12 2 10 11–12 2 9 12	2.800
	102.1359978	12 1 11 12–11 1 10 11	2.960
	109.7449013	13 5 9 13–12 5 7 12	4.703
	109.7938556	13 4 9 13–12 4 8 12	5.395
	110.0094549	13 2 11 13–12 2 10 12	3.300

	110.6333677	13 1 12 14–12 1 11 13	3.455
	126.6358855	15 5 10 15–14 5 10 14	6.200
	126.6960852	15 4 11 14–14 4 11 13	10.080
	133.9242154	16 1 16 15–15 0 15 16	4.730
	134.6750035	16 0 16 17–15 0 15 16	4.800
	135.148249	16 4 13 15–15 4 12 16	7.750
125–163 (ALMA band 4)	143.6023263	17 4 13 17–16 4 12 16	8.350
	151.9783682	18 5 14 18–17 5 12 17	8.100
	152.0568371	18 4 15 17–17 4 14 18	8.750
	160.4277999	19 5 14 18–18 5 13 19	8.575
	160.5135369	19 4 15 19–18 4 14 19	9.200

	168.9718077	20 4 16 20–19 4 15 20	9.250
	168.878091	20 5 16 20–19 5 15 19	9.00
	177.3296583	21 5 16 20–20 5 16 19	9.350
163–211 (ALMA band 5)	185.7821453	22 5 18 23–21 5 17 22	9.550
	185.8934615	22 4 18 22–21 4 17 22	8.350
	194.23659	23 5 19 22–22 5 17 22	10.520
	202.6910348	24 5 20 23–23 5 19 24	9.770

Note.

^aFor the transitions with the same J' ${k}_{a}^{{\prime} }$ ${k}_{a}^{{\prime} }$ ${k}_{c}^{{\prime} }$ ${k}_{c}^{{\prime} }$ – ${J}^{{\prime\prime} }$ ${J}^{{\prime\prime} }$ ${k}_{a}^{{\prime\prime} }$ ${k}_{a}^{{\prime\prime} }$ ${k}_{c}^{{\prime\prime} }$ ${k}_{c}^{{\prime\prime} }$ but having different vibrational state, please see the catalog in the propanimine.tar.gz package included with this article.

Download table as: ASCII Typeset image

Table 8. Non-LTE Modeling Line Parameters of Trans-ethylamine

Frequency Range (GHz)	Frequency (GHz)^a	Transition (J' ${k}_{a}^{{\prime} }$ ${k}_{c}^{{\prime} }$ v'– ${J}^{{\prime\prime} }$ ${k}_{a}^{{\prime\prime} }$ ${k}_{c}^{{\prime\prime} }$ ${v}^{{\prime\prime} }$ )	Intensity (K)
	31.4005744	5 1 4 0–5 0 5 0	0.0108
	33.06739330	2 0 2 0–1 0 1 0	0.0096
31–45 (ALMA band 1)	34.98500270	6 1 5 0–6 0 6 0	0.0129
	39.42887460	7 1 6 1–7 0 7 1	0.0152
	44.80634280	8 1 7 0–8 0 8 0	0.0173

	80.24199500	5 1 5 0–4 1 4 0	0.0534
	82.16878400	5 0 5 0–4 0 4 0	0.0569
67–90 (ALMA band 2)	82.67430100	5 2 4 0–4 2 3 0	0.0483
and	83.2428700	5 2 3 1–4 2 2 1	0.0486
84–116 (ALMA band 3)	84.98078500	5 1 4 1–4 1 3 1	0.0566
	98.30233700	6 0 6 0–5 0 5 0	0.0796
	101.886754	6 1 5 0–5 1 4 0	0.0806
	112.1583690	7 1 7 0–6 1 6 0	0.1016
	114.294235	7 0 7 0–6 0 6 0	0.1052
	115.604884	7 2 6 0–6 2 5 0	0.0996

	143.9269253	9 1 9 0–8 1 8 0	0.1586
	145.871741	9 0 9 0–8 0 8 0	0.1620
125–163 (ALMA band 4)	148.397949	9 2 8 1–8 2 7 1	0.1598
	159.753196	10 1 10 0–9 1 9 0	0.1878
	161.49643100	10 0 10 0–9 0 9 0	0.1914

	192.561480	12 0 12 0–11 0 11 0	0.2432
	197.25631220	12 2 11 1–11 2 10 1	0.2436
163–211 (ALMA band 5)	201.671390	12 1 11 0–11 1 10 0	0.2587
	203.166657	12 2 10 1–11 2 9 1	0.2534
	208.05354700	13 0 13 0–12 0 12 0	0.2565

Note.

^aFor the transitions with the same J' ${k}_{a}^{{\prime} }$ ${k}_{a}^{{\prime} }$ ${k}_{c}^{{\prime} }$ ${k}_{c}^{{\prime} }$ – ${J}^{{\prime\prime} }$ ${J}^{{\prime\prime} }$ ${k}_{a}^{{\prime\prime} }$ ${k}_{a}^{{\prime\prime} }$ ${k}_{c}^{{\prime\prime} }$ ${k}_{c}^{{\prime\prime} }$ but having different vibrational state, please see the cat file available at https://www.astro.uni-koeln.de/cdms/catalog.

Download table as: ASCII Typeset image

Table 9. Non-LTE Modeling Line Parameters of (1Z)-1-Propanimine

Frequency Range (GHz)	Frequency (GHz)^a	Transition (J' ${k}_{a}^{{\prime} }$ ${k}_{c}^{{\prime} }$ v'– ${J}^{{\prime\prime} }$ ${k}_{a}^{{\prime\prime} }$ ${k}_{c}^{{\prime\prime} }$ ${v}^{{\prime\prime} }$ )	Intensity (K)
	33.51992460	4 1 4 5–3 1 3 4	0.1192
	33.78887240	4 0 4 5–3 0 3 4	0.1269
31–45 (ALMA band 1)	41.89797460	5 1 5 6–4 1 4 5	0.1925
	42.25035000	5 2 3 6–4 2 2 5	0.1752
	42.58124550	5 1 4 6–4 1 3 5	0.1978

	76.62578210	9 1 8 10–8 1 7 9	0.6728
	83.76466100	10 1 10 11–9 1 9 10	0.7793
67–90 (ALMA band 2)	84.36429660	10 0 10 11–9 0 9 10	0.7906
and	84.56506570	10 2 8 11–9 2 7 10	0.7710
84–116 (ALMA band 3)	85.13188840	10 1 9 1–9 1 8 10	0.8215
	93.63540110	11 1 10 12–10 1 9 11	0.9333
	100.49611750	12 1 12 13–11 1 11 12	0.9232
	101.17028780	12 0 12 13–11 0 11 12	0.9826
	102.13600470	12 1 11 13–11 1 10 12	0.9689
	109.56052950	13 0 13 14–12 0 12 13	0.9616

	125.51588020	8 2 7 9–7 1 6 8	0.0591
	126.31319130	15 0 15 16–14 0 14 15	0.6378
125–163 (ALMA band 4)	127.00092650	15 2 13 16–14 2 12 15	0.3568
	127.61694790	15 1 14 15–14 1 13 14	0.3922
	134.67500350	16 0 16 17–15 0 15 16	0.3738

	175.64941420	9 3 7 10–8 2 6 9	0.09671
	175.80109580	9 3 6 10–8 2 7 9	0.09373
163–211 (ALMA band 5)	184.02040330	10 3 8 11–9 2 7 10	0.09697
	184.25941520	10 3 7 10–9 2 8 9	0.09647
	207.19739490	8 4 5 9–7 3 4 8	0.09612

Note.

^aFor the transitions with the same J' ${k}_{a}^{{\prime} }$ ${k}_{a}^{{\prime} }$ ${k}_{c}^{{\prime} }$ ${k}_{c}^{{\prime} }$ – ${J}^{{\prime\prime} }$ ${J}^{{\prime\prime} }$ ${k}_{a}^{{\prime\prime} }$ ${k}_{a}^{{\prime\prime} }$ ${k}_{c}^{{\prime\prime} }$ ${k}_{c}^{{\prime\prime} }$ but having different vibrational state, please see the catalog in the propanimine.tar.gz package included with this article.

Download table as: ASCII Typeset image

Chemical Modeling for Predicting the Abundances of Certain Aldimines and Amines in Hot Cores

Article metrics

Permissions

Author e-mails

Author affiliations

ORCID iDs

Dates

Abstract

1. Introduction

2. Computational Details and Methodology

2.1. Quantum Chemical Calculations

2.2. Chemical Modeling

3. Results and Discussions

3.1. CH₃N Isomeric Group

3.2. CH₅N Isomeric Group

3.3. C₂H₅N Isomeric Group

3.4. C₂H₇N Isomeric Group

3.5. C₃H₇N Isomeric Group

3.6. C₃H₉N Isomeric Group

4. Astrophysical Implications of This Work

5. Conclusions

: Appendix

Chemical Modeling for Predicting the Abundances of Certain Aldimines and Amines in Hot Cores

Article metrics

Permissions

Share this article

Author e-mails

Author affiliations

ORCID iDs

Dates

Abstract

1. Introduction

2. Computational Details and Methodology

2.1. Quantum Chemical Calculations

2.2. Chemical Modeling

3. Results and Discussions

3.1. CH3N Isomeric Group

3.2. CH5N Isomeric Group

3.3. C2H5N Isomeric Group

3.4. C2H7N Isomeric Group

3.5. C3H7N Isomeric Group

3.6. C3H9N Isomeric Group

4. Astrophysical Implications of This Work

5. Conclusions

: Appendix

3.1. CH₃N Isomeric Group

3.2. CH₅N Isomeric Group

3.3. C₂H₅N Isomeric Group

3.4. C₂H₇N Isomeric Group

3.5. C₃H₇N Isomeric Group

3.6. C₃H₉N Isomeric Group