An investigation into the effects of mixing in organic electrosynthesis
An investigation into the effects of mixing in organic electrosynthesis
The paired hydrodimerisation of methyl acrylate and dehydrodimerisation of diethyl malonate have been studied under a variety of mixing conditions in a number of electrochemical reactors (the bipolar pump cell, a capillary gap cell, a parallel plate cell and a trickle tower reactor). The main products and by-products have been identified and their distributions and yields explained semi-quantitatively in terms of the coupling of transport processes in the cells with possible reaction pathways. It has been shown that good dispersion of malonate anions is essential to prevent formation of Michael adducts and thus obtain high selectivities, but that too high a dispersion rate leads to lose of current efficiency through the parasitic iodine cycle. The class of the paired reaction has been extended to other activated olefins and carbon acids and the degree to which mixing determines the product distribution has been shown to depend on the reactivity of the olefin and the anion of the carbon acid.The acetaxylation of mesitylene in a parallel plate cell has also been studied systematically and has been found to be more sensitive to the kinetics of the chemical reactions of the electrogenerated intermediates rather than the mixing, contrary to earlier indications. Interestingly the replacement of acetate by formats as the supporting electrolyte produces both ring for moxylation and acetaxylation. Attempts to explain this have shown how little is known about the role which acetic acid plays as a solvent in electrolyses. It has been found that the interaction of mixing and contacting pattern with the rate of generation of intermediates and the rates of competing reactions can greatly affect the product distribution and current efficiency of many organic electrosyntheses and therefore it is unwise to do exploratory preparative syntheses under one set of arbitrarily chosen conditions.
University of Southampton
1980
Johnson, David Kenneth
(1980)
An investigation into the effects of mixing in organic electrosynthesis.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The paired hydrodimerisation of methyl acrylate and dehydrodimerisation of diethyl malonate have been studied under a variety of mixing conditions in a number of electrochemical reactors (the bipolar pump cell, a capillary gap cell, a parallel plate cell and a trickle tower reactor). The main products and by-products have been identified and their distributions and yields explained semi-quantitatively in terms of the coupling of transport processes in the cells with possible reaction pathways. It has been shown that good dispersion of malonate anions is essential to prevent formation of Michael adducts and thus obtain high selectivities, but that too high a dispersion rate leads to lose of current efficiency through the parasitic iodine cycle. The class of the paired reaction has been extended to other activated olefins and carbon acids and the degree to which mixing determines the product distribution has been shown to depend on the reactivity of the olefin and the anion of the carbon acid.The acetaxylation of mesitylene in a parallel plate cell has also been studied systematically and has been found to be more sensitive to the kinetics of the chemical reactions of the electrogenerated intermediates rather than the mixing, contrary to earlier indications. Interestingly the replacement of acetate by formats as the supporting electrolyte produces both ring for moxylation and acetaxylation. Attempts to explain this have shown how little is known about the role which acetic acid plays as a solvent in electrolyses. It has been found that the interaction of mixing and contacting pattern with the rate of generation of intermediates and the rates of competing reactions can greatly affect the product distribution and current efficiency of many organic electrosyntheses and therefore it is unwise to do exploratory preparative syntheses under one set of arbitrarily chosen conditions.
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Published date: 1980
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Local EPrints ID: 459113
URI: http://eprints.soton.ac.uk/id/eprint/459113
PURE UUID: 92e9f999-2254-49a0-b47b-a88a1da2f8ad
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Date deposited: 04 Jul 2022 17:04
Last modified: 04 Jul 2022 17:04
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Author:
David Kenneth Johnson
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