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Thermal analysis of novel biphenylamide derivatives: influence of positional and functional group isomerism on solid state properties

Thermal analysis of novel biphenylamide derivatives: influence of positional and functional group isomerism on solid state properties

Owusu-Ware, Samuel K., Cherry, Anthony J., Baltus, Christine B., Spencer, John and Antonijevic, Milan D. (2015) Thermal analysis of novel biphenylamide derivatives: influence of positional and functional group isomerism on solid state properties. Journal of Thermal Analysis and Calorimetry, 121 (1). pp. 437-452. ISSN 1388-6150 (Print), 1588-2926 (Online) (doi:10.1007/s10973-015-4628-7)

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Abstract

The physicochemical properties of a small library of 4-methyl-biphenylamide derivatives have been investigated by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and hot-stage microscopy (HSM). The obtained results show that positional isomerism has a significant influence on the thermal behaviour of the 4-methyl-biphenylamide derivatives. Two polymorphic forms were found for the ortho-substituted derivatives, whilst the para-substituted derivatives exhibit three polymorphic forms. The ortho-substituted biphenylamides were more likely to generate metastable forms when cooled from the melt. Furthermore, self-heating properties were revealed by the para-substituted 4-methyl-biphenylamide derivatives, in which the highly energetic crystallization processes raised the sample temperature by as much as 4°C during cooling. Such a high energy exothermic crystallization process suggests crystallization to be highly favourable, from a thermodynamic standpoint. Hence the p-substituted derivatives are unlikely to generate amorphous forms. Based on the melting points of the most stable polymorphic form (Form I) and the activation energy of the evaporation processes, the para-substituted compounds demonstrate greater thermal stability over their ortho-substituted counterparts. This further suggests that para-substituted compounds, due to their steric effects have greater interactions between individual molecules in the crystalline form.

Item Type: Article
Additional Information: The final publication is available at Springer via http://dx.doi.org/10.1007/s10973-015-4628-7
Uncontrolled Keywords: Biphenylamide derivatives, Polymorphism, stability, Crystallization, DSC
Subjects: Q Science > QC Physics
Q Science > QD Chemistry
Faculty / Department / Research Group: Faculty of Engineering & Science
Faculty of Engineering & Science > Department of Pharmaceutical, Chemical & Environmental Sciences
Last Modified: 17 Oct 2016 09:13
Selected for GREAT 2016: None
Selected for GREAT 2017: None
Selected for GREAT 2018: None
URI: http://gala.gre.ac.uk/id/eprint/13521

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