title: Thermochemistry and gas-phase ion energetics of 2-hydroxy-4-methoxy-benzophenone (oxybenzone).
abstract: We have investigated the thermochemistry and ion energetics of the oxybenzone (2-hydroxy-4-methoxy-benzophenone, C14H12O3, 1H) molecule. The following parameters have been determined for this species: gas-phase enthalpy for the of neutral molecule at 298.15K, (Delta(f)H0(m)(g) = -303.5 +/- 5.1 kJ x mol-1), the intrinsic (gas-phase) acidity (GA(1H) = 1402.1 +/- 8.4 kJ x mol-1), enthalpy of formation for the oxybenzone anion (Delta(f)H0(m)(1-,g) = -402.3 +/- 9.8 kJ x mol-1). We also have obtained the enthalpy of formation of, 4-hydroxy-4'-methoxybenzophenone (Delta(f)H0(m)(g) = -275.4 +/- 10 kJ x mol-1) and 3-methoxyphenol anion (Delta(f)H0(m)(C7H7O2-,g) = -317.7 +/- 8.7 kJ x mol-1). A reliable experimental estimation of enthalpy related to intramolecular hydrogen bonding in oxybenzone has also been obtained (30.1 +/- 6.3 kJ x mol-1) and compared with our theoretical calculations at the B3LYP/6-311++G** level of theory, by means of an isodesmic reaction scheme. In addition, heat capacities, temperature, and enthalpy of fusion have been determined for this molecule by differential scanning calorimetry.
authors.affiliation: Laboratório Nacional de Luz Síncrotron (LNLS), Box 6192, CEP 13084-971, Campinas-SP, Brazil.
authors.forename: A F
authors.initials: AF
authors.lastname: Lago
authors.forename: P
authors.initials: P
authors.lastname: Jimenez
authors.forename: R
authors.initials: R
authors.lastname: Herrero
authors.forename: J Z
authors.initials: JZ
authors.lastname: Dávalos
authors.forename: J-L M
authors.initials: JL
authors.lastname: Abboud