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Electrochemical reactivity in ionic liquid media

In our work, a number of reaction processes were investigated, using ionic liquids (ILs), or ionic liquid-based salts, as either the solvent or reactant. In chapter 3, the active form of TEMPO, the oxoammonium cation (T+), was used to synthesise T+ -bis(trifluoromethylsulfonyl)imide (NTf2) and T+trifluoromethanesulfonate (triflate) salts. These salts were used to investigate the mediated oxidation of primary alcohols. It was found that the oxidation process proceeded more rapidly for methanol than for the other two alcohols investigated. A significant drop in T+ current occurred when only base was added to the cell, with a multistep reaction process likely to be involved. The use of a solid DOWEX resin as base was also briefly investigated. In chapter 4, the electrocarboxylation of a number of benzophenone derivatives was investigated. For all investigated compounds, the carboxylation process proceeded via a ECE / DISPl mechanism. It has been found that the variation of the carboxylation reaction kinetics can be predicted based on the nature of the functional groups present on the benzene rings. Electron donating groups increased the rate of carboxylation, while electron withdrawing groups decreased the rate of carboxylation. The electrocarboxylation in I -butyl-lmethylpyrrolidinium bis-(trifluoromethane sulfonyl)imide [Bmpy][NTfz] were 2 orders of magnitude slower than those reported in DMF. In chapter 5, CO2 reduction in [Bmpy][NTfz] was briefly investigated at a number of electrode types (glassy carbon, platinum, palladium, gold, indium) using cyclic voltammetry. CO2 reduction was observed at all 5 electrodes, where it was found that Au and especially In act as electrocatalysts. The mediated reduction of COz in [Bmpy] [NTfz] was then attempted using methyl benzoate and dimethyl phthalate. Investigation of the electrochemistry of the two compounds in IL suggests that ion pairing causes an increase in the rate of dimerization over carboxylation, preventing the ester from acting as a redox mediator.

Identiferoai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:675853
Date January 2014
CreatorsMarley, Eunan
PublisherQueen's University Belfast
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation

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