Photocatalytic Oxidative Bromination of 2,6-Dichlorotoluene to 2,6-Dichlorobenzyl Bromide in a Microchannel Reactor

Abstract

Photocatalytic oxidative benzylic bromination with hydrobromic acid (HBr) and hydrogen peroxide (H 2 O 2 ) is a green process for the synthesis of benzyl bromides, but suffers from the risk of explosion when performing it in a batch reactor. This disadvantage could be overcome by running the reaction in a microchannel reactor. In this work, a green and safe process for the synthesis of 2,6-dichlorobenzyl bromide (DCBB) was developed by conducting selective benzylic bromination of 2,6dichlorotoluene (DCT) with H 2 O 2 as an oxidant and HBr as a bromine source in a microchannel reactor under light irradiation. The reaction parameters were optimized, and the conversion of DCT reached up to 98.1% with a DCBB yield of 91.4% under the optimal reaction conditions.

Whole-Teflon Lab on a Film

“…We optimized the inlet flow rates to 5 µL/min each, with a total flow rate of 10 µL/min, to achieve high mixing performance and prolonged residence time under UV exposure. Lower flow rates improve mixing efficiency by prolonging the time for molecular diffusion and increasing the residence time of the mixed reactants under UV exposure within the same distance [54][55][56][57] , resulting in a complete reaction on the microfluidic chip. The residence time of reactants in our microreactor was calculated to be approximately 136 s under the given flow rate.…”