title: Thermochemistry of 2- and 3-thiopheneacetic acids: calorimetric and computational study.
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.
authors.affiliation: Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Temprado
authors.forename: María Victoria
authors.initials: MV
authors.lastname: Roux
authors.forename: Pilar
authors.initials: P
authors.lastname: Jiménez
authors.forename: Concepción
authors.initials: C
authors.lastname: Foces-Foces
authors.forename: Rafael
authors.initials: R
authors.lastname: Notario
mesh_terms: D000085:Acetates / Q000737:chemistry*; D002151:Calorimetry; D003198:Computer Simulation; D004583:Electrons; D008956:Models, Chemical; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry; D011312:Pressure; D011789:Quantum Theory; D013696:Temperature; D013816:Thermodynamics; D013876:Thiophenes / Q000737:chemistry*
chemical_list: C517218:3-thiophene acetic acid; D000085:Acetates; D013876:Thiophenes; C017754:2-thienylacetic acid; D010100:Oxygen