Potential energy surface for unimolecular dissociations and rearrangementsof the ground state of [C2H3FO] systems

The potential energy surface (PES) of [C2H3FO] systems in its electronic gr ound state has been investigated using density functional theory method, at the B3LYP/6-311+ + G(d,p) level. Ten stable intermediates, including acety l fluoride (1), fluoroacetaldehyde (9), 1-fluorovinyl alcohol (4), 2-fluoro vinyl alcohol, carbenes and fluorooxiranes, have been located. Most station ary points on the PES corresponding to the molecular elimination and rearra ngement channels from these intermediates have been identified. Ketene (8) is found to be the predominant product in the unimolecular dissociations of 1, 4, 9 and fluorooxirane (6). The most probable channels for ketene forma tion from acetyl fluoride are 1 --> 8 and 1 --> 4 --> 8. In the reactions o f both CH3CO. and F-. radicals, both these processes are energetically feas ible for the thermal reactants and hence should lead to a spontaneous emiss ion of vibrationally hot HF. The present PES characterises the CH3CO. + F-. reaction to be a capture-limited association-elimination reaction with a v ery high and pressure-independent rate coefficient. In addition to its dire ct decomposition to ketene, 9 can give rise to stable rearrangement product s, viz., 2-fluorovinyl alcohol (12) and 6. Fluorooxirane (6) decomposes to ketene through its isomerisation to 9 as intermediate and the present study provides an explanation for the non-observation of this intermediate.