Experimental and computational estimation of standard
enthalpies of formation of the six trichlorophenols

 

Maria Luísa C. C. H. Ferrão, José R. B. Gomes and Manuel A. V. Ribeiro da Silva

 

Centro de Investigação em Química, Depto. de Química da Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 687, P-4169-007 Porto (Portugal)

 

The standard molar enthalpies of combustion in oxygen of each of the six trichlorophenols at T=298.15 K, were measured by rotating-bomb calorimetry from which the standard molar enthalpies of formation, in the crystalline phase were derived. The standard molar enthalpies of sublimation, at the temperature 298.15 K, were measured by Calvet microcalorimetry.

The derived standard molar enthalpies of formation of the gaseous compounds are compared with values estimated by accurate calculations based on Density Functional Theory (DFT). The B3LYP three-parameter hybrid method proposed by Becke[1] was used throughout all calculations, performed by means of the GAMESS-UK suite of programs.[2],[3] This method comprises an exchange-correlation functional that mixes the non-local Fock exchange with the gradient-corrected form of Becke[4] and adds the correlation functional proposed by Lee et al..[5] In the present approach, the atomic electron density was described by the standard polarized double-z split valence basis set DZVP.[6]