Theoretical study of the first step of SPLET mechanism: O–H bond cleavage in the mono-substituted benzoic acids

The first step of SPLET mechanism in solution phase for 15 benzoic acid derivatives was studied from the thermodynamic point of view. For this purpose, proton affinities (PAs) of corresponding carboxylate or phenoxide anions were computed by means of DFT method employing B3LYP and M062X functionals with 6-311++G** basis set and SMD or IEF-PCM solvent model. The substituent effect on PAs was analyzed in terms of Hammett constants, σ_p. Found dependences exhibit satisfactory linearity and enable quick estimation of solution phase PAs from the Hammett constants.