Zeolite Catalyzed Friedel-Crafts Acylations
Faculty Mentor Information
Dr. Leslie Nickerson (Mentor), Idaho State University
Abstract
Friedel-Crafts acylation reactions are traditionally catalyzed using a metal halide catalyst which acts as a Lewis acid. Due to product inhibition of the catalyst, metal halides are used in stoichiometric quantities which creates large amounts of toxic waste and is harmful to the environment. By replacing the metal halide with zeolites it is possible to make this process more sustainable. Zeolites are heterogenous, aluminosilicate compounds with micropores ranging from 0.1 - 2.0 nm and are easily recycled and safer to handle than the traditional metal halide catalysts. Our work thus far suggests that zeolite Y-hydrogen is the best catalyst for the acylation of m-xylene with benzoic acid to form 2,4-dimethylbenzophenone. Different silica to alumina ratios in Y-hydrogen zeolites, reflux time, drying agents, and nucleophile equivalences have also been explored. An expanded substrate scope is being explored with a variety of electron-donating and -withdrawing substituents on the nucleophile. Reactions with unprotected nucleophilic substrates (such as phenol and aniline) and benzoic acid have produced low conversions thus far, so we have begun to study the effect of substrate protection with silyl ether groups on conversion. Future work will consist of exploring more silyl ether protecting groups and electrophilic substrates with varying electron-donating and -withdrawing substituents as well as learning about zeolite selectivity for ortho/para products.
Zeolite Catalyzed Friedel-Crafts Acylations
Friedel-Crafts acylation reactions are traditionally catalyzed using a metal halide catalyst which acts as a Lewis acid. Due to product inhibition of the catalyst, metal halides are used in stoichiometric quantities which creates large amounts of toxic waste and is harmful to the environment. By replacing the metal halide with zeolites it is possible to make this process more sustainable. Zeolites are heterogenous, aluminosilicate compounds with micropores ranging from 0.1 - 2.0 nm and are easily recycled and safer to handle than the traditional metal halide catalysts. Our work thus far suggests that zeolite Y-hydrogen is the best catalyst for the acylation of m-xylene with benzoic acid to form 2,4-dimethylbenzophenone. Different silica to alumina ratios in Y-hydrogen zeolites, reflux time, drying agents, and nucleophile equivalences have also been explored. An expanded substrate scope is being explored with a variety of electron-donating and -withdrawing substituents on the nucleophile. Reactions with unprotected nucleophilic substrates (such as phenol and aniline) and benzoic acid have produced low conversions thus far, so we have begun to study the effect of substrate protection with silyl ether groups on conversion. Future work will consist of exploring more silyl ether protecting groups and electrophilic substrates with varying electron-donating and -withdrawing substituents as well as learning about zeolite selectivity for ortho/para products.