Standard molar enthalpies of formation of monochloroacetophenone isomers

The standard (p∘=0.1MPa) molar enthalpies of formation of the liquids 2′-, 3′-, and 4′-chloroacetophenones were derived from the standard molar energies of combustion, in oxygen, to yield CO2(g) and HCl · 600H2O(l), at T = 298.15 K, measured by rotating-bomb combustion calorimetry. The Calvet microcalorimetry was used to measure the enthalpies of vaporization of the three compounds. These two thermodynamic parameters yielded the standard molar enthalpies of formation of the chloroacetophenone isomers, in the gaseous phase, at T = 298.15 K.CompoundΔcu∘/(J·g-1)ΔfHm∘(g)/(kJ·mol-1)2′-Chloroacetophenone−25939.6 ± 2.7−99.4 ± 2.13′-Chloroacetophenone−25862.5 ± 2.7−107.4 ± 2.44′-Chloroacetophenone−25802.7 ± 2.7−117.6 ± 2.5An empirical scheme, developed by Cox, was used to estimate the gas-phase enthalpies of formation and the obtained values were compared with the experimental ones.