Ultrasound-Assisted Green Synthesis of Dialkyl Peroxides under Phase-Transfer Catalysis Conditions

Daniel Kopeć,Stefan Baj,Agnieszka Siewniak

doi:10.3390/molecules25010118

Daniel Kopeć, Stefan Baj + Show 1 more

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https://doi.org/10.3390/molecules25010118

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Abstract

The dialkyl peroxides, which contain a thermally unstable oxygen–oxygen bond, are an important source of radical initiators and cross-linking agents. New efficient and green methods for their synthesis are still being sought. Herein, ultrasound-assisted synthesis of dialkyl peroxides from alkyl hydroperoxides and alkyl bromides in the presence of an aqueous solution of an inorganic base was systematically studied under phase-transfer catalysis (PTC) conditions. The process run in a tri-liquid system in which polyethylene glycol as a phase-transfer catalyst formed a third liquid phase between the organic and inorganic phases. The use of ultrasound provided high yields of organic peroxides (70–99%) in significantly shorter reaction times (1.5 h) in comparison to reaction with magnetic stirring (5.0 h). In turn, conducting the reaction in the tri-liquid PTC system allowed easy separation of the catalyst and its multiple use without significant loss of activity.

Highlights

The phase-transfer catalysis (PTC) is a well-established technique in the synthesis of compounds with important practical applications in pharmaceuticals, agrochemicals, fragrances, dyes, monomers, and others [1]. It is a special type of heterogeneous catalysis in which the reaction occurs between reagents that are located in two phases in the presence of a phase-transfer catalyst
Work, we we described described the the efficient efficient method method of of the the dialkyl dialkyl peroxides peroxides synthesis synthesis from from
We examined the effect of the alkyl chain length of the alkyl bromide on the peroxide yield under the most favorable reaction conditions obtained on the basis of the present study (50% KOH, KOH to cumyl hydroperoxide (CHP) of 20:1, PEG MM 2000, and cyclohexane)

Summary

Introduction

The phase-transfer catalysis (PTC) is a well-established technique in the synthesis of compounds with important practical applications in pharmaceuticals, agrochemicals, fragrances, dyes, monomers, and others [1]. It is a special type of heterogeneous catalysis in which the reaction occurs between reagents that are located in two phases in the presence of a phase-transfer catalyst. PTC catalysts are often quaternary ammonium salts, crown ethers, or polyethylene glycols. The benefits of using PTC are minimization or elimination of organic solvents, the use of accessible, cheap and often safer reagents The dialkyl peroxides are readily used as radical polymerization initiators, e.g., in the polymerization of olefins and as crosslinking agents, e.g., for ethylene–propylene copolymers, silicone rubbers, and others [3,4]

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