Abstract or Keywords
Phenylboronic acids (PBAs) are an important class of compounds with diverse applications in synthetic, biological, medicinal, and materials chemistry. In this investigation we report structural and thermochemical parameters for several monosubstituted ortho, meta, and para PBAs, R-B(OH)(2) (R = C6H5, C6H4CH3, C6H4NH2, C6H4OH, and C6H4F). Equilibrium geometries of all the PBAs discussed in this article were obtained using second-order Moller-Plesset perturbation theory (MP2) with the Dunning-Woon aug-cc-pVDZ basis set; heats of formation (HOF) were calculated at the Gaussian-3 (G3) level of theory. The endo-exo conformers of all the positional isomers of these PBAs were lowest in energy. Using HOF for the monosubstituted PBAs calculated at the G3 level of theory, in conjunction with the experimental HOF for benzene, toluene, aniline, phenol, and fluorobenzene, the values of for the transfer processes C (6) H (6) + C (6) H (4) X -aEuroeB(OH)(2) -> aEuroeC (6) H (5) X + C (6) H (5) -aEuroeB(OH)(2)(X = CH3,NH2, OH, and F) are found to be in good agreement with values of Delta H calculated at the MP2(FC)/aug-cc-pVTZ//MP2(FC)/aug-cc-pVTZ computational level; the bonding in the reactants and products for these transfer reactions is well-matched and thermochemical calculations at this level are expected to be very accurate, providing checks on the G3 HOF calculations.