Thermochemistry of 2- and 3-thiopheneacetic acids: calorimetric and computational study.

Manuel Temprado, María Victoria Roux, Pilar Jiménez, Concepción Foces-Foces, Rafael Notario

Index: J. Phys. Chem. A 112(41) , 10378-85, (2008)

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Abstract

The enthalpies of formation in the condensed and gas states, Delta f H m degrees (cd) and Delta f H m degrees (g), of 2- and 3-thiopheneacetic acids were derived from their respective enthalpies of combustion in oxygen, measured by a rotating bomb calorimeter, and the variation of vapor pressure with temperature determined by the Knudsen effusion technique. Theoretical calculations at the G3 level were performed, and a study on molecular and electronic structure of the compounds has been carried out. Calculated Delta f H m degrees (g) values using atomization and isodesmic reactions are compared with the experimental data. Experimental and theoretical results show that the 3-thiopheneacetic acid is thermodynamically more stable than the 2-isomer.