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首页> 外文期刊>Journal of thermal analysis and calorimetry >Relationship between crystal structure and thermal properties of polymorphic system methylethanolammonium 2-chloro-4-nitrobenzoate
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Relationship between crystal structure and thermal properties of polymorphic system methylethanolammonium 2-chloro-4-nitrobenzoate

机译：Relationship between crystal structure and thermal properties of polymorphic system methylethanolammonium 2-chloro-4-nitrobenzoate

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摘要

The crystal structures and thermal characteristics of two polymorphs of methylethanolammonium 2-chloro-4-nitrobenzoate were investigated by a combined experimental and computational approach. The main attention was paid to the synthesis of polymorphs, structural characterization associated with computational studies on the nature of intermolecular interactions, and thermodynamic stability relationship between the polymorphs and thermal decomposition kinetics. Analysis of the polymorphs structure revealed distinct crystal packing arrangements and different numbers of independent molecules pairs in the asymmetric crystal unit. Depending on the conformation of cations, polymorphs alpha and beta exhibit the formation of different charge-assisted and normal hydrogen bonds, while in beta, non-covalent interactions of halogens are also manifested. The calculated values of the lattice energies indicated that alpha has a more stable lattice than beta at high temperatures. The thermodynamic stability relationship between the polymorphs pair is monotropic and is determined by measuring melting points and heats of fusion. The kinetics of thermal decomposition processes has been comparatively studied by two different kinetic methods. The results showed higher activation energies for alpha compared to beta. According to the modified nonparametric kinetic method, the decomposition mechanism revealed two distinct stages in both polymorphs, indicating one predominant chemical degradation process followed by a physical transformation process.

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