Direct C(sp3)–H chloromethylation through CH2Cl2 activation using non-thermal plasma

Abstract

Non-thermal plasma has been implemented for chemical activation of CH₂Cl₂ in a continuous flow gas–liquid system operating at ambient temperature and pressure. In this study, we present a direct and catalyst-free approach for the chloromethylation of saturated hydrocarbons. The reaction test resulted in the functionalization of cyclohexane without a catalyst or additives, achieving a total yield of 30% of chlorinated products with a residence time of 60 s. The influence of substrate concentration, gas/liquid flow ratio, energy density and residence time was studied, which resulted in a proposal of reaction pathway where the reaction is initiated by the C–Cl dissociation in CH₂Cl₂, followed by H-abstraction on C(sp³)–H and radical recombination. These mechanistic insights provide valuable knowledge for the advancement of plasma chemistry. Furthermore, the use of deuterated dichloromethane allows the introduction of deuterium into saturated hydrocarbons.