Abstract
The present thesis constitutes a study, with particular reference to stereochemical considerations, of the type of quadrivalency which is exhibited by the tellurium at in its organic compounds. Organic tellurides were prepared, a method being developed for the production of dialkyl tellurides in quantity. Symmetrical telluronium salts were formed, examined, and composed to similar salts of sulphur and selenium. Mixed dialkyl tellurides were obtained by breaking down these salts, and asymmetric telluretine salts then prepared analogous to the thetine salts of Smiles. The resolution of these asymmetric compounds was attempted, partial resolutions being effected in some instances. The course of oxidation of an unsymmetrical ditelluretine salt which oxidised on exposure to the atxaos- phere was investigated. Products were isolated which showed that oxidation had proceeded to a very advanced stage. Di-n-butyl telluride and mixed dialkyl tellurides were oxidised by various agents, the course of oxidation being studied. The oxidation products were found to be complex, but were consistently of a type which permitted comparisons to be drawn with the courses of oxidation of sulphides and selenides. In no case was a telluroxide thus obtained alone; nor could it be isolated from its complex. The suggestion is advanced to explain this inability to isolate telluroxides that the tellurium atom does not fora stable compounds in which it exerts two covalencies and one semi-polar double bond and that the charge on the telluroxide oxygen atom is neutralised by combination with an acidic hydrogen atom. The evidence in favour of this suggestion is reviewed. A pheasulphtellurine [mathematical formula], analogous to Drew's phenoxtellurine, was prepared with a view to examining a sulphoxide- telluroxide oxidation product in cis- and trans-isomeric forms could be obtained. Oxidation products were prepared and examined, and it was shown that the sulphur and tellurium atoms resisted systematic oxidation. Conclusions are drawn, from the present results and from the work of previous investigators, as to the nature of the quadrivalency shown by tellurium in organic compounds.