Thermodynamic properties of aqueous solutions of pyridine and piperidine

doi:10.1016/j.fluid.2009.10.018

Fluid Phase Equilibria

Volume 290, Issues 1–2, 25 March 2010, Pages 95-102

https://doi.org/10.1016/j.fluid.2009.10.018 Get rights and content

Abstract

This research was designed to examine the thermodynamic properties of aqueous solutions of pyridine and piperidine. The density, excess molar enthalpy of mixing, H^E, and excess molar volume of mixing, $v^{E}$ of piperidine–water and pyridine–water mixtures were studied at three temperatures, ranging from 294 K to 315 K. The H^E and $v^{E}$ are negative for both mixtures, minimizing at a water mole fraction of about 0.55. The minimum H^E for piperidine–water mixtures is −2.23 kJ/mol which is compared with −1.63 kJ/mol for pyridine–water mixtures. The minimum $v^{E}$ are about −1.7 cm³/mol and −0.7 cm³/mol for piperidine–water and pyridine–water mixtures, respectively. The thermal expansion coefficients α_T at 303 K, calculated from the density studies, exhibited significant positive deviations (about 20%) from ideality for piperidine–water mixtures. In contrast to this pyridine–water α_T only exhibited small positive deviations from ideality of about 2%. The results predict decreases in the absolute magnitude of $v^{E}$ with an increase in temperature which are 5. × 10⁻³ cm³/K mol and 1. × 10⁻³ cm³/K mol, for piperidine–water and pyridine–water mixtures, respectively. The results for $v^{E}$ for piperidine–water mixtures agree with the very precise work of Afzal et al., J. Chem. Thermodyn. 40 (2008) 47–53. The data are interpreted in terms of the greater number of opportunities for hydrogen bonding interactions between the unlike molecules for the piperidine–water mixtures.

Introduction

Thermophysical properties of liquids and liquid mixtures are needed for both fundamental and practical applications. Excess thermodynamic properties provide information on the interactions between molecules of the liquid mixtures and the liquid structure. Therefore the study of the connection between thermodynamics and other fields, particularly transport phenomena, mathematical modeling and kinetics, is encouraged in both Chemistry and Chemical Engineering.

The study of the thermodynamic properties of amines and their mixtures with water is of interest due to the common existence of amines in nature (nicotine, morphine, amphetamine, etc.) and their applications in chemical processes. In this context both piperidine and pyridine are used in variety applications especially as solvents and reagents in organic synthesis [1], [2], [3].

Afzal et al. [4] recently published a very excellent and comprehensive study of the density and excess volume of piperidine–water mixtures over a wide range of temperatures. Negative volumes of mixing are reported in this work. However no comparable studies have been reported on the excess enthalpy of mixing. In this paper excess enthalpies of mixing are reported for both piperidine–water and pyridine–water mixtures. The density and excess volumes of mixing as a function of temperature over the entire concentration range are also investigated for both mixtures. The density measurements on piperidine–water mixtures provide a comparison with the previous work of Afzal et al. [4] that is a valuable check on our techniques. The results are interpreted in terms of the hydrogen bonding interactions between the unlike molecules and the very open tetrahedrally hydrogen bonded water structure in pure liquid water. The interpretations include discussions of the similarities and differences between piperidine and pyridine, piperidine being the aliphatic analogue of pyridine which adds a hydrogen to the amine nitrogen. This hydrogen provides opportunity for an additional hydrogen bonding interaction between piperidine and water.

Section snippets

Experimental

Pyridine and piperidine were purchased from Aldrich with a purity of 99.8% and 99%, respectively. The chemicals were used without further purification. Deionized water with a 99.99% purity was used in the experiments. The excess enthalpies of mixing, denoted as H^E were measured with a Parr 6755 Constant Pressure Solution Calorimeter. Water and the amine of interest were titrated, using 50-mL burettes, into separate containers. The lesser volume was contained in a rotating sample cell whereas

Calorimetric studies

The enthalpy of mixing is calculated from the temperature rise, ΔT, measured in the solution calorimeter experiment using the equation, $Δ H_{m} = q = - C Δ T,$ where ΔH_m is the enthalpy change for the mixing process, q is the heat absorbed or released upon mixing, and C is the heat capacity of the calorimeter and its contents. The value of C is calculated using the relation $C = n_{1} C_{p, 1} + n_{2} C_{p, 2} + 51.1$ where n₁ and n₂ represent the moles of the respective components and $C_{p, 1}$ , and $C_{p, 2}$ are the heat capacities of the

Conclusions

The excess molar enthalpy H^E and excess molar volumes $v^{E}$ of both piperidine–water and pyridine–water mixtures are negative reaching their minimum 0.55 mole fraction of water. The minimum value of H^E for piperidine–water mixtures is −2.23 kJ/mol and −1.63 kJ/mol for pyridine–water mixtures. The minimum values for $v^{E}$ of piperidine–water mixtures (−1.7 cm³/mol) are more than twice the magnitude for those for pyridine–water mixtures (−0.7 cm³/mol).

The dominant intermolecular interactions affecting H^E

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Topological investigations of molecular interactions in binary and ternary mixtures at varying temperatures and atmospheric pressure: Excess molar volumes and excess isentropic compressibilities
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Liquids with their provenance, purification, analysis methods, initial as well as final mass fraction purities with water content are specified in Table 1. Purity of the liquids was assessed by comparing ρ, u of liquids [26-48] with literature data. ρ, u of binary/ternary mixtures were measured by vibrating tube density, speed of sound analyzer (Anton Paar, DSA-5000) at 3 MHz in a manner as described earlier [49,50].
Densities, speeds of sound of 1-methylpyrrolidin-2-one (NMP) (1) + piperidine (2) + cyclopentanone (CPO), cyclohexanone (CHO), cycloheptanone (CHPO) (3) and the involved binary NMP (1) + piperidine (2) mixtures have been measured as a function of composition at temperatures from (293.15 - 308.15) K range in a step of 5 K and atmospheric pressure. Excess molar volumes, $V^{E}$ ; excess isentropic compressibilities, $κ_{S}^{E}$ of the current mixtures have been determined using experimental data and correlated to composition using Cibulka and Redlich–Kister equations. Also, binary and ternary adjustable parameters along with standard deviations between measured and derived values via Cibulka and Redlich-Kister equations have been estimated. The $V^{E}$ , $κ_{S}^{E}$ have also been assessed in terms of Graph and Prigogine-Flory-Patterson theories. Observed results suggest that Graph theory prophesies the most appropriate results.
Characterization of multicomponent mixtures containing piperidine, 1-methylpiperidine, 2-pyrrolidinone and isomeric picolines
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Thermodynamic data of liquid mixtures are utilized for testing thermodynamic models/theories, which in turn may provide various parameters that could be utilized for industrial applications. Piperidine is used as solvent (due to its mild basic properties) in the field of biochemistry and industrial processes [9,10]. Piperidine and 1-methylpiperidine are also structural elements of many pharmaceutical drugs [11,12].
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Thermodynamic characterisation of aqueous alkanolamine and amine solutions for acid gas processing by transferable molecular models
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The development of new alkanolamines/amines is a topic which has attracted a great deal research interest, particularly as absorbents for the removal of acid gases from industrial sources and CO₂ capture applications. One of the major challenges when evaluating the techno-economic performance of selected new single amines or blends is the lack of experimental data on the thermophysical properties required for a reliable process design and simulation. In this contribution, a robust theoretical framework for the description of key thermophysical properties of aqueous solutions of single and mixed alkanolamines/amines at relevant gas separation process conditions is proposed. The approach is based on the coupling of the Free-Volume Theory and the Density Gradient Theory with a molecular-based equation of state (soft-SAFT) for the integrated modelling of phase behaviour, enthalpies, densities, viscosities and interfacial tensions. The alkanolamines and amines investigated differ in their family and structure, and included primary (monoethanolamine), secondary (diethanolamine), tertiary (methyldiethanolamine), sterically hindered (2-amino-2-methyl-1-propanol) and cyclic amines (piperazine). The study was performed in a systematic manner, starting from the development of the models for the pure amines, the description of their thermophysical properties, and the properties of the aqueous mixtures. Compared to other models described in literature, the present modelling approach preserves the effects due the chemical structure and key intermolecular interactions of the examined alkanolamines/amines through a set of molecular parameters obtained from pure substance data, whenever available, or transferred from substances of different chemical families. This enabled the development of a consistent modelling framework which can provide reliable thermodynamic property predictions of both single and blended amine solutions over a broad range of temperatures (298–373 K) and compositions (0–50 wt% amine). The proposed approach is well-suited for implementation and extension to other alkanolamines and amines, making it a valuable tool for having reliable process simulations as well as for the screening and discovery of new amine systems, which will be required for the deployment of more economical acid gas removal processes.
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The results are presented in Fig. 7. In the same figure are also shown the viscosity values for the pyridine–water solution are also shown [35,36]. It appears that the trend is similar for both M2 and viscosity.
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Likewise piperidine derivatives are useful as CCR5 inhibitors e.g. in the prevention or treatment of disorders mediated by interactions between chemokine receptors and their ligands. [5] Recently, we reported our results on thermodynamic properties of aqueous solutions of unsubstituted pyridine and piperidine at three different temperatures. [6] We have now extended these studies to two structural isomers of pyridine and piperidine methanols to evaluate the effect of the primary alcohol functional group on the inter/intramolecular and additional hydrophilic interactions.
The objective of this research was to carry out a comparative study of the volumetric properties of 2-pyridinemethanol, 3-pyridinemethanol, 2-(hydroxymethyl)piperidine, and 3-(hydroxymethyl)piperidine in aqueous media. The density and excess volumes of mixing as a function of temperature (T = 293.15–318.15 K) over the entire concentration range are examined for aqueous solutions of 2,3-pyridinemethanols, and the density and partial molar volumes of aqueous solutions are investigated for the corresponding 2,3-(hydroxymethyl)piperidines. The minimum values of the excess molar volumes, v^E, are observed, −0.59 cm³ mol⁻1 for 2-pyridinemethanol–water solutions and −0.47 for 3-pyridinemethanol–water solutions. These are about 0.61% and 0.49% respectively, of the molar volume. The thermal expansion coefficients α_T at 298.15 K calculated from the density data, exhibited significant positive deviations, (about 30%) from ideality for 2-pyridinemethanol–water mixtures, and 3-pyridinemethanol–water mixtures. The partial molar volume of 2,3-(hydroxymethyl)piperidines in water at selected temperatures was evaluated by extrapolating the apparent molar volume versus molality plots to m = 0. In addition, the partial molar expansivity, E⁰, the isobaric coefficient of thermal expansion, α_T, the interaction coefficient, S_v, and the Hepler's constant have also been computed. The data are interpreted in terms of the effect of the primary alcohol functional group on the inter/intramolecular and additional hydrophilic interactions between the molecules.

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¹: Completed portions of this work to fulfill undergraduate research requirements for a BS degree in Chemistry.

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Thermodynamic properties of aqueous solutions of pyridine and piperidine

Abstract

Introduction

Section snippets

Experimental

Calorimetric studies

Conclusions

J. Chem. Thermodyn.

Thermochim. Acta

Encyclopedia of Reagents for Organic Synthesis

Ullmann's Encyclopedia of Industrial Chemistry

Organic Chemistry