The work described in part I of this thesis is concerned with the development of a number of approaches designed to generate alkyl metaphosphates in solution. In each approach the final reaction step involves the crucial breakdown of a suitable precursor with a σ-bond being both broken and formed at a central phosphorus atom. Two main routes to alkyl metaphosphates were investigated. The first involved the condensation of a novel disodium pyrocarbonate salt with alkyl dichlorophosphates to form cyclic pyrocarbonate phosphates. These novel cyclic phosphates then underwent chelotropic breakdown with the release of two moles of carbon dioxide to produce alkyl metaphosphates. The second route investigated involved the condensation of potassium hydrogen carbonate with an alkyl dichlorophosphate to form a mixed anhydride. Upon warming breakdown of the mixed anhydride occurred, with the release of one mole each of hydrogen chloride and carbon dioxide to produce alkyl metaphosphates. In each case when the reactions were repeated in the presence of epoxides, the alkyl metaphosphates were trapped with the formation of 1,3,2-dioxophospholane-2-oxides. This reaction was valuable in providing evidence for the intermediacy of alkyl metaphosphates and demonstrated unequivocally their high electrophilic character. <SUP>31</SUP>P NMR spectroscopy was found to be an invaluable tool for following the course of the reactions being investigated. This was demonstrated by the fact that when alkyl metaphosphates were formed in the absence of trapping reagents, self-condensation occurred to give linear and cyclic polyphosphates which were easily identified by <SUP>31</SUP>P NMR signals in the δ-10 and -20 ppm regions. When trapping by epoxides was carried out these signals were replaced by a closely matched pair of peaks in the range δ 16-18 ppm which were unique to diastereomeric mixtures of cyclic phosphates having five membered rings.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:653394 |
| Date | January 1995 |
| Creators | Kilgour, Derek |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/10993 |
Page generated in 0.014 seconds