Continuous generation, in-line quantification and utilization of nitrosyl chloride in photonitrosation reactions

Abstract

Herein, we describe a continuous flow protocol for the generation, purification and quantification of nitrosyl chloride (NOCl). The generation of this useful but hazardous reagent is based on the reaction of aqueous NaNO₂ with HCl as readily available starting materials. The reagent, which is formed immediately upon mixing of the reactants, is rapidly extracted into a suitable organic phase, such as CHCl₃ or CH₂Cl₂, and separated using a continuous flow liquid–liquid membrane separator. A convenient method for the in-line monitoring of reagent concentration, based on flow UV/vis analysis, has also been developed and implemented. The synthetic utility of the nitrosyl chloride generator was demonstrated by integrating a continuous flow photochemical reactor downstream to perform the synthesis of cyclohexanone oxime from cyclohexane, an important industrial process.