The reaction of N(4S) with CH2F:: A comparative ab initio and DFT study

The triplet potential energy surface for the N(S-4) + CH2F((2)A') reaction has been studied employing both MP2 and DFT(B3LYP) methods. The energies of the involved species have been refined using the G2, CBS, and CCSD(T) methods, respectively. The general picture for this reaction is a typical addition-elimination mechanism, where initially a rather stable intermediate, (NCH2F)-N-. ., is obtained by the interaction of nitrogen with the radical through the carbon atom. There are two preferred products from the thermodynamic viewpoint, trans-FC.=NH and HFC=N-., the latter one being slightly more stable. Other possible products, such as H2C=N-. and trans-HC.=NH, are also exothermic but less stable, whereas cis-HC.=NF is even clearly endothermic. From the kinetic viewpoint, HFC=N-. is predicted to be the preferred product. It seems that neither isomerization nor subsequent elimination of hydrogen or fluorine atoms from the primary products is feasible, since all these processes are much less exothermic and involve considerable kinetic barriers.