| Abstract
| - A detailed computational study is performed on the radical−molecule reaction between the vinyl radical(C2H3) and formaldehyde (H2CO), for which only the direct hydrogen abstraction channel has been consideredby previous and very recent theoretical studies. At the Gaussian-3//B3LYP/6-31G(d) and CBS-QB3 levels,the direct H-abstraction forming C2H4 + HCO has barriers of 3.9 and 4.7 kcal/mol, respectively. The additionbarrier to form H2CCHCH2O has barriers of 2.8 and 2.3 kcal/mol, respectively. Subsequently, there are twohighly competitive dissociation pathways for H2CCHCH2O: One is the formation of the direct H-extrusionproduct H2CCHCHO + H, and the other is the formation of C2H4 + HCO via the intermediate H2CCH2CHO. Surely, the released energy is large enough to drive the secondary dissociation of HCO to H + CO.Because the involved transition states and intermediates of the H2CCHCH2O evolution all lie energeticallylower than the entrance addition transition state, the addition−elimination is more competitive than the directH-transfer for the C2H3 + H2CO reaction, in contrast to previous expectation. The present results can beuseful for future experimental investigation on the title reaction.
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