Thermochemical study of anthranilate derivatives: Effect of the size of the alkyl substituent

Abstract

The gas-phase enthalpies of formation of two fragrance compounds, methyl anthranilate and butyl anthranilate, at T = 298.15 K, were determined from the combination of the corresponding enthalpies of vaporisation and energies of combustion, obtained from Calvet microcalorimetry and combustion calorimetry measurements, respectively. Additionally, theoretical calculations were performed, using the G3(MP2)//B3LYP composite method, to estimate the gas-phase enthalpies of formation of the two fragrance compounds. The good agreement between the experimental and computational gas-phase enthalpies of formation of the methyl anthranilate and butyl anthranilate, provided the confidence for extending the theoretical study to propyl anthranilate. Furthermore, the results were interpreted in terms of enthalpic increments, aiming to evaluate and understand the energetic effect inherent to the alkyl group (methyl, ethyl, propyl or butyl) present in the ester functional group of the anthranilate derivatives.