O–H Bond dissociation enthalpies in hydroxyphenols. A time-resolved photoacoustic calorimetry and quantum chemistry studyElectronic supplementary information (ESI) available: Table S1: Total energies calculated at the MPW1PW91/aug-cc-pVDZ and the CBS-4M levels. Data include zero point energies and thermal corrections to 298 K. See http://www.rsc.org/suppdata/cp/b3/b314093h/

Time-resolved photoacoustic calorimetry TR-PAC was used to investigate the energetics of O–H bonds of phenol, catechol, pyrogallol, and phloroglucinol. Values of −27.1 ± 3.9, −44.1 ± 4.4 and −1.6 ± 3.8 kJ mol−1, respectively, were obtained for the solution-phase acetonitrile O–H bond dissociation enthalpies of the last three compounds relative to the O–H bond dissociation enthalpy in phenol, ΔDHoslnArO–H  DHoslnArO–H − DHoslnPhO–H. A value of 388.7 ± 3.7 kJ mol−1was determined for the PhO–H bond dissociation enthalpy in acetonitrile. Density functional theory MPW1PW91aug-cc-pVDZ calculations and complete basis set CBS-4M calculations were carried out to analyse intramolecular hydrogen bonding and to predict gas-phase O–H bond dissociation enthalpies, DHoArO–H. A microsolvation model, based on the DFT calculations, was used to study the differential solvation of the phenols and their radicals in acetonitrile and to bridge solution- and gas-phase data. The results strongly suggest that ΔDHoslnArO–H  ΔDHoArO–H. Hence, to calculate absolutegas-phase O–H bond dissociation enthalpies in substituted phenols from the corresponding solution-phase values, the solvation enthalpies of the substituted phenols and their radicals are notrequired.