Title:
|
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.
|