Experimental and computational study of the molecular energetics of the monoiodoanisole isomers

The standard (p degrees = 0.1 MPa) molar enthalpies of formation, in the condensed phase, of the three monoiodoanisoles, were derived from the respective enthalpies of combustion, measured by rotating-bomb combustion calorimetry. Their enthalpies of sublimation/vaporization, at T = 298.15 K, were obtained by Calvet microcalorimetry using the high-temperature vacuum sublimation technique. Moreover the standard molar enthalpy, entropy and Gibbs energy of sublimation, at T = 298.15 K, of 4-iodoanisole were derived from the Knudsen mass-loss effusion technique. Combining the former sets of experimental results, the standard molar enthalpies of formation in the gas-phase, at T = 298.15 K, of 2-, 3- and 4-iodoanisole were derived, respectively, as: (15.1 +/- 2.1) kJ . mol (1); (11.8 +/- 2.2) kJ . mol (1), and (12.4 +/- 1.6) kJ . mol (1). The experimental values of the gas-phase enthalpies of formation of each iodoanisole were also estimated by means of the empirical scheme developed by Cox and by density functional theory calculations employing the B3LYP/6-311++G(d, p) approach. Estimated values are in excellent agreement with the reported experimental ones derived in the present paper. (C) 2011 Elsevier Ltd. All rights reserved.