Crystal structure and thermodynamic properties of myclobutanil

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Highlights

  • Myclobutanil belongs to monoclinic system with space group P21/c.

  • Its low melting point is mainly due to the weak hydrogen bonds and halogen bond.

  • The Cp,m of myclobutanil was determined by calorimeter and theoretical calculation.

  • The Cp,m of myclobutanil is 362.78 J·K−1·mol−1 at T = 298.15 K.

Abstract

Myclobutanil is a high-efficiency, low toxicity and wide spectrum triazole fungicide. Its crystal structure was characterised by single-crystal X-ray diffraction, which belongs to monoclinic system with space group P21/c. The molecules are linked by weak hydrogen bonds and halogen bond to from a 3D structure. This is the main reason for its low melting point. The specific molar heat capacity (Cp,m) of myclobutanil was determined by a continuous Cp mode of micro-calorimeter and theoretical calculation, and the Cp,m of myclobutanil was 362.78 J·K−1·mol−1 at T = 298.15 K.

Introduction

Myclobutanil (C15H17N4Cl; CASRN: 88671-89-0), chemically named α-butyl-α-(4-chlorophenyl)-1H-1,2,4-triazole-1-propane nitrile, is a high-efficiency, low toxicity and wide spectrum triazole fungicides [1]. It is used in control of Ascomycetes, Fungi Imperfecti and Basidiomycetes on a wide variety of crops [2], [3]. For example, it used for a foliar treatment to control the scab in apples and pears; powdery mildew in apples, pears, stone fruit, vines, cucurbits and ornamentals; rust in ornamentals, stone fruit and perennial grasses grown for seed; and various diseases in wheat; it also used for a seed treatment to control the seed- and soil-borne diseases in crops such as barley, wheat maize, cotton and rice.

In this paper the crystal structure of myclobutanil was reported. The specific molar heat capacity (Cp,m) of myclobutanil was determined by continuous Cp mode of micro-calorimeter and theoretical calculation.

Section snippets

Materials

Myclobutanil was obtained from Jiangsu Greenscie Chemical Co., Ltd. The colourless single crystal of myclobutanil (CCDC 907765) was obtained by recrystallisation from absolute ethyl alcohol. The mass fraction purity of single crystal of myclobutanil was measured by high performance liquid chromatography (HPLC type Shimadzu LC-10AT, infusion pump type LC-10ATvp, detector type SPD-10Avp, the mobile phase is acetonitrile and water with 60% (V/V)) and found to be above 0.999 (Table 1). The melting

Crystal structure

Single-crystal analysis shows the compound crystallises in monoclinic space group P21/c, with Z = 4. Myclobutanil is a chiral molecule (Fig. 2), R- and S-myclobutanil through hydrogen bond of C8single bondH8A⋯Cl (Table 4) forms a 0D structure (Fig. 3), indicating the myclobutanil is a racemate. From Fig. 4, one can see that each 0D structure is crossed connected with four 0D structure through hydrogen bond of C3single bondH3A···N1 and halogen bond of C13single bondCl⋯N1 to from a 2D structure. The distance of adjacent 0D

Conclusions

Crystal structure of myclobutanil belongs to monoclinic system with space group P21/c, with Z = 4, it is a racemate. Its low melting point is mainly due to its 3D structure is formed by the weak intermolecular hydrogen bonds and halogen bond. The Cp,m equation of myclobutanil is Cp,m/(J·K−1·mol−1) = −26.21315 + 1.30468 (T/K) from T = (283.15 to 353.15) K and the Cp,m is 362.78 J·K−1·mol−1 at T = 298.15 K. The relative deviations of Cp,m, HT  H298.15 K and ST  S298.15 K are almost equivalency at each temperature,

Note

All the uncertainties in the text are standard uncertainties.

Acknowledgments

This work was supported by New Century Excellent Talents in University of Ministry of Education of China (No. NCET-12-1047), the National Natural Science Foundation of China (Nos. 21373161, 21543016), the Provincial Natural Science Foundation of Shaanxi (No. 2014JQ2068) and the Startup Foundation for Advanced Talents of Yulin University (No. 14GK28).

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