Calorimetric study of 2′-methylacetophenone and 4′-methylacetophenone

Abstract

Values of the condensed phase standard (p=0.1MPa) molar enthalpy of formation for 2′- and 4′-methylacetophenones were derived from the standard molar energies of combustion, in oxygen, at T=298.15K, measured by static bomb combustion calorimetry. The values of the standard molar enthalpy of vaporization, at T=298.15K, were measured by Calvet microcalorimetry. Combining these two values, the following enthalpies of formation in the gas phase, at T=298.15K, were then derived: 2′-methylacetophenone, –(115.7±2.4)kJ·mol−1, and 4′-methylacetophenone, –(122.6±2.4)kJ·mol−1. Substituent effects are discussed in terms of stability and compared with other similar compounds. The value of the standard molar enthalpy of formation for 3′-methylacetophenone was estimated from isomerization schemes.