Studies in Crystal Structures

Silverton, J. V (1963) Studies in Crystal Structures. PhD thesis, University of Glasgow.

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This thesis embodies the results of investigations into two dissimilar aspects of X-ray crystallography, hence the rather general title "Studies in Crystal Structure." The first part concerns a study of the crystal structure of Tris (methylsulphonyl) methane, a somewhat unusual organic compound, which is an acid of strength comparable with hydrochloric acid. Two aspects of this structure re of interest, firstly the molecular geometry, because of theoretical speculation previous to the work, and secondly the fact that the crystals give rise to an unusual form of diffuse scattering of X-rays. That the two aspects are not independent was shown in the course of the investigation. It was impossible to account for the intensities of the Bragg reflexions on a basis of any ordered structure. These intensities can only refer to structure which is an average taken over the whole crystal and the nature of this 'average structure' was deduced, a ter much work in two dimensions, by the use of three-dimensional data and vector and Fourier methods. The average structure involves partial occupancy of sites in the unitcell whose positions are related by a centre of symmetry, not required by the space-group. The two sites do not appear to be occupied equally. The results of a least-squares refinement of the average structure are given. The residual is 9% and thus the molecular structure is known to a fair degree of accuracy. The structure appears to contradict the previously mentioned theoretical ideas. The bond lengths and angles are comparable with those in similar compounds. The nature of the average structure has been used as a starting point for investigations of the disorder with the help of on optical diffractometer. Details are given of the finding of a fairly small unit which gives rise to an optical transform similar to the X-ray photographs. The extension of this model to the whole crystal is also considered. The second part of the thesis concerns work in a more conventional field of crystal chemistry; that of alkaloid structure. Details are given of the investigation of the crystal structure of the alkaloid Calycanthine, derived from the poisonous shrub, Calycanthus aureus. The structure of this compound as known only partially at the start of the work. The structure was studied initially by two-dimensional methods and, while partial success in the Location of the atoms in the crystals of the hydro- bromide of the alkaloid was attained by the method of 'generalized projections', the crystal structure was not solved completely until three-dimensional act mods, using the 'heavy-atom' technique, were employed.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Physical chemistry
Date of Award: 1963
Depositing User: Enlighten Team
Unique ID: glathesis:1963-79480
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 05 Mar 2020 09:05
Last Modified: 05 Mar 2020 09:05

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