Ab initio quantum chemical studies of reaction mechanism for CH 2CO with NCO

Abstract

An extensive quantum chemical study of the potential energy surface (PES) for all possible isomerization and dissociation reactions of CH 2CO with NCO is reported at the DFT (B3LYP/6-311++G(d,p)) and CCSD(T)/cc-pVDZ//B3LYP/6-311++G(d,p) levels of theory. For the CH 2CO+NCO reaction, the formation of CO+CH 2NCO via an addition–elimination mechanism is the dominant channel on the doublet surface. While the formation of CO+CH 2OCN via bimolecular substitution reaction is in the secondary. Meanwhile, the isomerization and dissociation reactions of the products, CH 2NCO and CH 2OCN, also have been investigated using the same theoretical approach. It can be concluded that these reaction channels are not feasible kinetically at low or fairly high temperatures. On the basis of the ab initio data, the total rate constants for the CH 2CO+NCO reaction in the T=296–560 K range have been computed using conventional transition state theory with Wigner tunneling correction and fitted by a rate expression as k=2.14×10 −12 (cm 3 molecule −1 s −1) exp(654.29/ T). The calculated total rate constants with Wigner tunneling correction for the CH 2CO+NCO reaction are in good agreement with the available experimental values.