Journal of Physical Chemistry A, Vol.112, No.14, 3201-3208, 2008
Thermochemistry and gas-phase ion energetics of 2-hydroxy-4-methoxy-benzophenone (oxybenzone)
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 H-f(m)0(g) = -303.5 +/- 5.1 kJ.mol(-1)), the intrinsic (gas-phase) acidity (GA(1H) = 1402.1 +/- 8.4 kJ.mol(-1)), enthalpy of formation for the oxybenzone anion (Delta(f) H-m(0)(1(-),g) = -402.3 +/- 9.8 kJ-mol(-1)). We also have obtained the enthalpy of formation of, 4-hydroxy-4'-methoxybenzophenone (Delta H-f(m)0(g) = -275.4 10 kJ.mol(-1)) and 3-methoxyphenol anion (Delta H-f(m)0(C7H7O2-,g) -317.7 +/- 8.7 kJ.mol(-1)). A reliable experimental estimation of enthalpy related to intramolecular hydrogen bonding in oxybenzone has also been obtained (30.1 +/- 6.3 kJ-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.