A theoretical study of the geometry of the first triplet of acetaldehyde and of its fragmentation into free radicals

The energy profiles for the decomposition of the first triplet of acetaldehyde via the reactions: CH 3 CHO ν → CH 3 CO° + H°, CH 3 CHO * → CH . 3 + HCO . , have been computed using a non-empirical LCAO MO SCF procedure. Both reactions were found to have energy barriers of similar height (245 KJ mole −1 ) and at similar extensions of the respective rupturing bonds (0.71–0.76 A). The energy profile for internal rotation about the C-C bond was also calculated and showed a small barrier (3.5 kJ mole −1 ).