The study of the PES and the reaction mechanism between ketene and Lithium Carbenoids and the formation of cyclopropanone

We present a theoretical analysis of the reaction mechanisms on Lithium Carbenoids LiCH2X (X = F, Cl y Br) and ketenes at B3LYP/6-311++G(d,p) level at the IRC. We have considered the implicit solvation effects of dichloromethane using the PCM methodology. For the reaction coordinate analysis, we have used the reaction force analysis and the theoretical tools coming from conceptual DFT, NBO populations and NCI. The reaction mechanism has a barrierless step corresponding to the interaction of the carbenoid and the hydrogen of the ketene alpha carbon and a single kinetic step representing the bonding of the carbon carbenoid to the ketene alpha carbon, the activation of the reaction proceeds mostly by electrostatic interactions perpendicular to the molecular plane followed by a rotation of the ketene showing the influence of the ionic nature of the carbenoid, and the following formation of the bond with the ketene beta carbon atom. All three reactions are highly exothermic leading to a decomposition product that is far lower in energy than the cyclopropanone. The tendency of the reaction barriers is LiCH2Br < LiCH2Cl < LiCH2F, indicating that the bromine carbenoid is the most reactive molecule of this group.