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Title: Studies in gas chromatography with reference to volatile inorganic compounds
Author: Simpson, C. C.
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 1968
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The major part of the work described in this thesis is concerned with the development of the techniques of closed-circuit gas chromatography, as originally derived from conventional chromatography by Timms, for the separation and identification of certain volatile silicon and germanium compounds. These techniques were devised to extend the work, classically carried out in high-vacuum distillation systems, to more complex mixtures and smaller samples. In addition to the development work on the basic method, development work was carried out on components and systems, in particular, detector circuitry, a cheap and simple method of temperature control for chromatographic columns, the deoxidisation of nitrogen supplies, and traps for high efficiency removal of volatiles from gas streams. In its final form, the closed-circuit chromatographic apparatus consisted essentially of a preparative gas chromatograph, fitted with two columns and fraction collection traps, and equipped with facility for the recycling of samples, combined with an analytical system. The analytical system consisted of a two-column gas chromatograph equipped with a gas density detector for quantitative analysis of mixtures, provided the components could be identified. Analyses were either effected on products of reactions carried out in external apparatus, or on the products of the reaction of compounds, purified in the preparative system, passed in a nitrogen stream through a reactor containing anhydrous AuCl3. This reactor with its ancilliary apparatus was fitted as part of the analytical system. The system of a reactor containing gold chloride heated to 170°C effectively in series with a quantitative gas chromatograph was devised by Timms as a technique for the elucidation of the empirical formulae of the silicon-germanium hydrides, SinGemH2(n-hn)+2, which were quantitatively chlorinated to yield SiCl4, GeCl4 and HCl. In this work this technique was developed for the analysis of compounds of silicon and germanium with alkyl groups. Initially it was attempted to convert the tetramethyls and tetraethyls to the tetrachlorides and chlorinated hydrocarbons by reactions under severe conditions. Although this proved feasible, it was realised that partial chlorination under milder conditions should give structural information as well as empirical formulae, provided that all the products could be identified. When the gold chloride reaction, under a variety of conditions, was carried out on GeMe4, and the methyl germanium chlorides, it was discovered that chlorination of the methyl groups could occur without Ge-C bond fission. In particular, loss of methyl groups from GeMe2Gl2 and GeMeCl3 mainly occurred after a stepwise chlorination to CCl3.GeMeCl2 and CCl3.GeCl3. All of the members of the series CClnH3-n.GeMemCl3-m (n = 1 to 3, m = 0 to 3) were tentatively identified by their reactions and by gas chromatographic data. In view of the large range of products obtained under these intermediate conditions, it was decided to attempt the reaction of gold chloride at temperatures only between 30° and 90°C, under which conditions no side chain chlorination would be expected to occur. As such, the technique was employed to determine the empirical formulae and, in particular, the structures of the permethyl silanes and permethyl germanes, as the anticipated products of Si-Si and Ge-Ge fission only, the methyl silicon and germanium chlorides were not expected to react further to any great extent.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available