The reactant cluster and transition state for epoxidation of allyl alcohol with peroxyformic acid have been located at the MP2/6-31G(d) level of theory, The free energy of activation (Delta(278)double dagger = 19.8 kcal/mol) predicted at the MP4 parallel to MP2/6-31G(d) level is quite comparable with experimental data for epoxidation of 3-hydroxycyclohexene (Delta G(278)double dagger = 19.7 kcal/mol), A spiro transition state (TS) was found where the plane defined by the peroxyacid moiety is oriented at 89 degrees to the C-C bond axis. Intrinsic reaction coordinate analysis suggests that after the barrier is crossed a 1,4-hydrogen migration of the peroxyacid hydrogen to the carbonyl oxygen takes place in concert with O-O bond cleavage affording the epoxide of allyl alcohol hydrogen bonded to the neutral formic acid leaving group, The activation parameters calculated at the B3LYP/6-311G(d,p) level are ill excellent agreement with the MP4 parallel to/MP2 values, The transition structure with the allyl alcohol O-C-C=C dihedral angle of 16.4 degrees is 2.1 kcal/mol lower in energy than a transition structure with a dihedral angle of 134.3 degrees. The directing effect of the hydroxyl group is attributed initially to a primary hydrogen bonding interaction between the relatively more acidic peroxy acid proton and the oxygen of the allyl alcohol. In both the reactant complex 1 and the transition structure (TS-2) for oxygen atom transfer the alcohol remains hydrogen bonded to the more basic carbonyl oxygen of the peroxyacid, The G2 proton affinities (PA(298)) of the carbonyl oxygen and the proximal peroxo oxygen of peroxyformic acid are 177.1 and 153.3 kcal/mol, respectively.