Three separate systems have been investigated. Firstly, the electrochemical reduction of some cyclic immonium salts has been examined by means of polarography, cyclic voltammetry, coulometry and preparative electrolysis using aprotic solvents (CH3CN and DM1') as the medium. The immonium salts were reduced to their two-electron reduction products but only one electron per mol was exchanged. The observation of the corresponding enamine among the products led to an investigation of the mechanism by linear sweep voltammetry and stereochemical analysis. This showed that the immonium cations were reduced to neutral radicals which underwent a radical-radical disproportionation reaction involving hydrogen-atom transfer. The effects of proton donors, ion-pairing and adsorption were also investigated. The second study concerned the reduction of acetophenone and 3-methylcinnamonitrile in dry (ca. 100ppm H20) CH 3CN. Products resulting from attack of the conjugate base of the solvent upon the substrate, 3-hydroxy-3-phenylbutanenitrile and 3-methyl-3-phenylglutaronitrile among others, were observed in addition to the usual dimerization products. The residual water in the solvent has been shown to play a crucial role, the participation of OH- ions being implicated in the formation of _CH2CN ions which then form an adduct with the depolariser. It has been proposed that the residual water affects the stereochemistry of the dimers and that dimerization takes place in solution. Evidence for adsorption has been presented but this does involve the dimerization process. The third study involved the reductive cleavage of the cyclopropyl ring in certain 1-cyclopropyl yylidenemalononitriles in aprotic solvents. Linear sweep voltammetry and stereochemical analysis have shown that the cleavage proceeds via a radical-ion and that the cleavage mechanism is radical in character. The cleavage reaction has been shown to be reversible for 2,2-di-alkylsubstituted cyclopropyl rings and irreversible for less substituted rings.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:653318 |
| Date | January 1977 |
| Creators | Kerr, John Borland |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/12357 |
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