Studies of Ylides and of Two Synthetic Intermediates by X-Ray Analysis

Hair, Neil John (1972) Studies of Ylides and of Two Synthetic Intermediates by X-Ray Analysis. PhD thesis, University of Glasgow.

Abstract

In this thesis the techniques of crystal structure analysis are applied to the study of bonding and molecular conformation. The contents are divided into three parts, and in PART I various theoretical aspects of the methods of structure determination are discussed, with special emphasis being placed on the Direct Methods of structure elucidation which are used extensively in this research. PART II is concerned with the study, by X-ray analysis, of five Ylide-type compounds. In an attempt to rationalise the little-studied bonding systems and conformations exhibited by such molecules, the crystal structures of the three first-row ylides N-trimethylamraonio-benzamidate, N-trimethyl-ammonio-nitramidate and (+)-3-diazocamphor, and of the two second-row ylides N-(p-toluenesulphonyl)-iminodimethyl-sulphur(IV) and N-(p-toluenesulphonyl)-iminotriphenyl-phosphorane have been determined. The results of these analyses allow trends in the stability of this class of compound to be examined in relation to the bonding interactions involved, and in the case of second-row ylides, the possible involvement in the bonding of d-orbitals of the second-row element can be examined. The final section of PART II is devoted to comparisons with the structures of other relevant molecules, in an effort to further investigate bonding and conformational trends in this class of chemical compound. Moreover, an interesting correlation is suggested between the bonding interactions involved in ylides and the conformations adopted by these molecules. Accounts of the structure analyses of two terpenoid synthetic intermediates are contained in PART III. A knowledge of the relative stereochemistries of the diol systems in both 2beta-carbomethoxy-5alpha,6alpha-dihydroxy-7,7-dimethyl-tricyclo[6.2 1.01,6] undecane and also the unsubstituted derivative of 2a-carbomethoxy-5beta-chloroacetoxy-7,7-dimethyl-tricyclo[6.2.1.0 1,6] undecan-6beta-ol is essential to a better understanding, in mechanistic terms, of the novel rearrangements of these compounds. The overall similarity of both systems, but yet differing relative stereochemistries, provide an opportunity to study in detail the changes which may result from alterations in the relative stereochemistries of substituents and ring fusions. Interesting features reproduced in both molecules are the long C(sp3)-C(sp3) bonds (ca. 1.59 A) connecting completely substituted, eclipsed sp3 centres, probably the result of the strain inherent in these bonds. Finally, the thesis contains several published papers by the author, two of which are not otherwise included in the contents. Both describe the crystal structure analysis of 5-methoxycarbonylmethylene-2-piperidino-2-thiazolin-4-one, the addition product of N-thiocarbamoylpiperidine and Dimethylacetylenedicarboxylate, a reaction which has caused considerable speculation.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Organic chemistry, Analytical chemistry, Physical chemistry
• Date of Award: 1972
• Depositing User: Enlighten Team
• Unique ID: glathesis:1972-78594
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 30 Jan 2020 15:09
• Last Modified: 30 Jan 2020 15:09
• URI: https://theses.gla.ac.uk/id/eprint/78594