Experimental and Computational Thermochemical Study of the Three Monofluorophenol Isomers
journal contributionposted on 10.09.2009, 00:00 by Manuel A.V. Ribeiro da Silva, Ana I. M. C. Lobo Ferreira
The present work reports the values of the standard (po = 0.1 MPa) molar enthalpies of formation in the condensed phase of the three isomers of monofluorophenol derived from the standard molar energies of combustion, in oxygen, to yield CO2(g) and HF·10H2O(l), at T = 298.15 K, measured by rotating bomb combustion calorimetry, as well as the values of the standard molar enthalpies of sublimation or vaporization, at T = 298.15 K, determined using high temperature Calvet microcalorimetry. Combining the former two experimental quantities, the standard molar enthalpies of formation in the gaseous phase were derived, at T = 298.15 K: ΔfHmo(2-fluorophenol, g) = −(294.5 ± 1.6) kJ·mol−1, ΔfHmo(3-fluorophenol, g) = −(292.8 ± 1.7) kJ·mol−1, and ΔfHmo(4-fluorophenol, g) = −(287.6 ± 2.1) kJ·mol−1. The experimental values of the gas-phase enthalpies of formation of each compound were compared with estimates using the empirical scheme developed by Cox and with the calculated values based on high-level density functional theory calculations using the B3LYP hybrid exchange−correlation energy functional at the 6-311++G(d,p) basis set.