Abstract :
A thermophysical study by differential scanning calorimetry (DSC) for the 2- and 3-isomers of thiophenecarboxylic acid, in the temperature intervals between T=268 K and their respective melting temperatures has been carried out, and enhancements in the heat capacity curves were observed. The supramolecular structure of both compounds was analysed by X-ray crystallography and IR spectroscopy to determine which structural modifications take place in the temperature range at which the heat absorption occurs. Changes in bands assigned mainly to δ(OH) + ν(CO), δ(CH) + ν(CS) and out of plane CH vibrations point to structural modifications taking place in the temperature range at which the heat absorption occurs. All those groups are involved in the weak CH⋯O or CH⋯S contacts that form the crystal three-dimensional network and so it can be concluded that changes in these H-bond strength, are responsible for the small heat absorptions founded in the heat capacity curves.
