The adsorption of methanol on aluminum (100) surface is modeled by quantum mechanical calculations on a small cluster, using hybrid Hartree-Fock/density functional theory. The enthalpy of adsorption at low coverage is calculated for the high-symmetry sites. The relevance of tipping of the prevalent methoxy species before C-O bond scission is examined. A new mechanism for dissociation is proposed, which is in excellent agreement with experimental determinations of the energy of activation for dissociation. Principles of transition-state theory are correlated to theoretical calculation of vibrational frequencies. Current assumptions from molecular orbital theory, as applied to surface reaction energetics, are called into question.