Theoretical Study on the Reaction Mechanism of Ketene CH₂CO with Isocyanate NCO Radical

Abstract

The bimolecular single collision reaction potential energy surface of an isocyanate NCO radical with a ketene CH 2 CO molecule was investigated by means of B3LYP and QCISD(T) methods. The computed results indicate that two possible reaction channels exist on the surface. One is an addition-elimination reaction process, in which the CH 2 CO molecule is attacked by the nitrogen atom at its methylene carbon atom to lead to the formation of the intermediate OCNCH 2 CO followed by a C-C rupture channel to the products CH 2 NCO＋CO. The other is a direct hydrogen abstraction channel from CH 2 CO by the NCO radical to afford the products HCCO＋HNCO. Because of a higher barrier in the hydrogen abstraction reaction than in the addition-elimination reaction, the direct hydrogen abstraction pathway can only be considered as a secondary reaction channel in the reaction kinetics of NCO＋ CH 2 CO. The predicted results are in good agreement with previous experimental and theoretical investigations.