This work describes the investigation of a range of reactions involving the catalysis of organic sulphur compounds by ion-exchanged sheet silicates (mainly AT W- and H -exchanged bentonite). The reactions of thiols, dithiols, sulphides and alkene/thiol mixtures have been studied in depth. Analysis of the products of these reactions was carried out mainly by gas chromatography (G.C.), coupled gas chromatography-mass spectrometry (G.C.-M.S.) and nuclear magnetic resonance (N.M.R.). In the majority of cases, confirmation of product identity has been via a direct comparison of G.C. and G.C.-M.S. data from synthetic or authentic samples. Kinetic studies on some of these reactions have provided thermochemical data. This research has shown that thiole (R-SH) will react with themselves in the presence of ion-exchanged sheet silicates to form dialkyl sulphides (R-S-R)i with alkenes to form various addition products and with alkynes to form a mixture of mono and di-substituted compounds. The reaction of benzene thiol has yielded large quantities of benzene while -toluene thiol formed a polymeric compound. The sheet silicates have also catalysed reactions involving dithiole and cyclic sulphides. This work has revealed that an extremely wide range of both known and novel types of organic chemical reactions are efficiently catalysed by certain ion-exchanged bentonites and that intercalation is a prerequisite. From this survey a mechanistic generalisation has emerged in which the role of the catalyst as a donor of protons or Lewis acid sites is crucial and the attack of a nucleophile on the resulting species being the key mechanistic process.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:637021 |
| Date | January 1983 |
| Creators | Galvin, R. P. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
Page generated in 0.0017 seconds