Electrochemical reduction of aromatic ketones in 1-butyl-3-methylimidazolium-based ionic liquids in the presence of carbon dioxide: the influence of the ketone substituent and the ionic liquid anion on bulk electrolysis product distribution
| Autor: | Jie Zhang, Shu-Feng Zhao, Alan M. Bond, Michael D. Horne |
|---|---|
| Rok vydání: | 2015 |
| Předmět: |
chemistry.chemical_classification
Ketone Tetrafluoroborate Molecular Structure Carboxylic acid Inorganic chemistry Imidazoles Ionic Liquids General Physics and Astronomy Electrochemical Techniques Carbon Dioxide Ketones Electrolysis Product distribution chemistry.chemical_compound chemistry Ionic liquid Benzophenone Physical and Theoretical Chemistry Oxidation-Reduction Trifluoromethanesulfonate Acetophenone |
| Zdroj: | Physical Chemistry Chemical Physics. 17:19247-19254 |
| ISSN: | 1463-9084 1463-9076 |
| DOI: | 10.1039/c5cp00095e |
| Popis: | Electrochemical reduction of aromatic ketones, including acetophenone, benzophenone and 4-phenylbenzophenone, has been undertaken in 1-butyl-3-methylimidazolium-based ionic liquids containing tetrafluoroborate ([BF4](-)), trifluoromethanesulfonate ([TfO](-)) and tris(pentafluoroethyl)trifluorophosphate ([FAP](-)) anions in the presence of carbon dioxide in order to investigate the ketone substituent effect and the influence of the acidic proton on the imidazolium cation (C2-H) on bulk electrolysis product distribution. For acetophenone, the minor products were dimers (10%) in all ionic liquids, which are the result of acetophenone radical anion coupling. For benzophenone and 4-phenylbenzophenone, no dimers were formed due to steric hindrance. In these cases, even though carboxylic acids were obtained, the main products generated were alcohols (50%) derived from proton coupled electron transfer reactions involving the electrogenerated radical anions and C2-H. In the cases of both acetophenone and benzophenone, the product distribution is essentially independent of the ionic liquid anion. By contrast, 4-phenylbenzophenone shows a product distribution that is dependent on the ionic liquid anion. Higher yields of carboxylic acids (∼40%) are obtained with [TfO](-) and [FAP](-) anions because in these ionic liquids the C2-H is less acidic, making the formation of alcohol less favourable. In comparison with benzophenone, a higher yield of carboxylic acid (30% versus ∼15%) was obtained with 4-phenylbenzophenone in all ionic liquids due to the weaker basicity of 4-phenylbenzophenone radical anion. |
| Databáze: | OpenAIRE |
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