Theoretical study on the reaction mechanism of vinyl radical with formyl cyanide

A detailed computational study is performed on the radical-molecule reaction between the Vinyl radical (C2H3) and formylcyanide (HCOCN). At the B3LYP/6-311G** and CCSD levels, the barrier of H-abstraction to provide (C2H4 + COCN) is 19.2 and 35.1 kJ/mol, respectively. The barrier of the addition to form H2CCHCOHCN is 9.1 and 15.5 kJ/mol, respectively. Subsequently, there is only one highly competitive dissociation pathway for H2CCHCOHCN: the formation of C2H4 + COCN via the intermediate H2CCH2COCN. Thanks to the influence of the strong electron acceptor-CN to the acyl, both the involved transition states and intermediates of the H2CCHCOHCN evolution lie energetically lower than the entrance addition transition state, the addition-elimination is more competitive than the direct H-transfer which results in C2H3 + HCOCN reaction, which ridiculously contradict to previous expectation. The present results can be useful for future experimental investigation on the title reaction.