Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

The standard (p 1/4 0:1 MPa) massic energy of combustion, in oxygen, of the crystalline 3-acetyl-2- methyl-5-phenylthiophene was measured, at T = 298.15 K, by rotating-bomb combustion calorimetry, from which the standard molar enthalpy of formation, in the condensed phase, was calculated as DfH mocrP 1/4 o104:3 3:1P kJ mol 1. The corresponding standard molar enthalpy of sublimation, at T = 298.15 K, Dg crH m 1/4 o108:9 0:4P kJ mol 1, was derived by the Clausius Clapeyron equation, from the temperature dependence of the vapour pressures of this compound, measured by the Knudsen effusion mass-loss technique. From the results presented above, the standard molar enthalpy of formation, in the gaseous phase, at T = 298.15 K, was derived, DfH mogP 1/4 o4:6 3:1P kJ mol 1. This value, in conjunction with the literature values of the experimental enthalpies of formation of thiophene, 2-methylthiophene, and 3-acetylthiophene, was used to predict the enthalpic increment due to the introduction of a phenyl group in the position 2- of the thiophene ring. The calculated increment was compared with the corresponding ones in benzene and pyridine derivatives.