X-Ray Studies of Some Organic Crystal Structures

Cox, Philip John (1972) X-Ray Studies of Some Organic Crystal Structures. PhD thesis, University of Glasgow.

Abstract

This thesis describes the crystal and molecular structures of a number of organic molecules. Both the heavy atom method and direct methods were used in the elucidation of these structures. Three derivatives of 2-(6'-methoxy-2'-naphthyl)-1-methyl-5-oxocyclopentane-1-acetate have been examined and the structures determined. The alcohol derivative possesses oestrogenic activity and X-ray analysis has shown that this molecule contains both intramolecular and intermolecuiar hydrogen bonds between two hydroxyl groups. The intramolecular oxygen-oxygen distance can be regarded as completing a six-membered ring of the chair type. Configurations of the lactone and ether derivatives, suggested by I.R. and N.M.R. spectra, were shown by X-ray analysis to be incorrect. These molecules were in fact found to contain cyclohexane rings and not the expected cyclopentane rings. This is direct evidence of a Wittig reaction involving a novel rearrangement. The structure of 9-methylanthracene was previously obtained from two-dimensional X-ray data by H. K. L. Verma, this structure has been completely redetermined using diffractometer data. Although the unit cell dimensions in this study and in the previous study were almost identical the packing of the molecules in the crystal is different. Either the four molecules of the unit cell are capable of packing in two different ways or the structure obtained from the limited two-dimensional data was incorrect. Preliminary crystal data of 9-methyltetracene have also been obtained. An X-ray study of 6B-Trimethylammonio-penicillanic acid hemihydroiodide was undertaken to determine if a short, symmetrical hydrogen bond was present. It was found that the carboxyl groups of the two penicillin moieties in the Zwitter ion are linked by a short crystallographically symmetrical hydrogen bond with the oxygen-oxygen separation 2.46 A. The stereochemistries of three sesquiterpene-lactones, supplied by Werner Herz of Florida University, have been determined via non-centrosymmetric direct method procedures. Dihydromikanolide contains a highly strained carbocyclic ten-membered ring which adopts an unsymmetrical conformation. The two epoxide groups on this ring are in the anti-position and the stereochemistry at C(13) has been determined. The atoms C(15) and H(5) in miscandenin are syn to each other and the remaining stereochemistry of the molecule has been obtained. The configuration of the third sesquiterpene, berlandin, was uncertain and the stereochemistry of the molecule was completely unknown prior to X-ray analysis. These have been fully determined; the acyl side chains were found at C(8) and C(9). The appendix contains the crystal and molecular structures of 17,20beta,21-trihydroxypregn-4-en-3-one 17,21-p-bromophenylborate and N-2-(2,4-dimethyl-1-pyrrolidinyl)-ethyl-p-iodobenzene-sulphonamide. The data obtained for the former were limited, and although the stereochemistry of the molecule was determined high standard deviations were associated with the final results. The crystal structure of the iodobenzene-sulphonamide derivative may be disordered as very high temperature factors were associated with many of the atoms in this molecule.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Organic chemistry, Molecular chemistry, Physical chemistry
• Date of Award: 1972
• Depositing User: Enlighten Team
• Unique ID: glathesis:1972-78606
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 30 Jan 2020 15:08
• Last Modified: 30 Jan 2020 15:08
• URI: https://theses.gla.ac.uk/id/eprint/78606