High level ab initio stabilization energies of benzene

G2 theory is shown to be reliable for calculating isodesmic and homodesmotic stabilization energies (ISE and HSE, respectively) of benzene. G2 calculations give HSE and ISE values of 92.5 and 269.1 kJ mol(-1) (298 K), respectively. These agree well with the experimental HSE and ISE values of 90.5 +/- 7.2 and 268.7 +/- 6.3 kJ mol(-1), respectively. We conclude that basis set superposition error corrections to the enthalpies of the homodesmotic or isodesmic reactions are not necessary in calculations of the stabilization energies of benzene using G2 theory. The calculated values of the enthalpies of formation of such molecules containing multiple bonds such as benzene and s-trans 1,3-butadiene, which are found from the enthalpies of isodesmic and homodesmotic reactions rather than of atomization reactions, demonstrate good performance of G2 theory. Estimates of the Delta H-f(o) value for benzene from the G2 calculated enthalpies of homodesmotic reaction (2) and isodesmic reaction (3) are 80.9 and 82.5 kJ mol(-1) (298 K), respectively. These are very close to the experimental Delta H-f(o) value of 82.9 +/- 0.3 kJ mol(-1). The Delta H-f(o) value of s-trans 1,3-butadiene calculated using the G2 enthalpy of isodesmic reaction (4) is 110.5 kJ mol(-1) and is in excellent agreement with the experimental Delta H-f(o) value of 110.0 +/- 1.1 kJ mol(-1) .