The Crystal Structures of Some Organic Molecules

Trotter, James (1957) The Crystal Structures of Some Organic Molecules. PhD thesis, University of Glasgow.

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This thesis deals with the elucidation of the crystal and molecular structures of some organic molecules using X-ray diffraction methods. The thesis is divided into four parts. In Part I the process of X-ray crystal analysis is described briefly, and some methods of overcoming the fundamental difficulty in crystal analysis - the phase problem - and obtaining an approximate structure are outlined. Many investigations however are undertaken with the object of obtaining accurate molecular dimensions, and methods of refining a structure are described in Part II. The use of (Fo - Fc ) syntheses is illustrated by the refinements of the crystal structures of p-benzoquinone and coronene. More accurate values of the bond lengths and valency angles in benzoquinone have been obtained, and these agree reasonably well with those obtained in an electron-diffraction Investigation of the vapour, and with those in related molecules. In the coronene refinement, the discrepancies between measured and calculated bond lengths have been reduced, and the hydrogen atoms have been resolved. Part III describes the analysis of the structure of dinaphthoperopyrene, an "overcrowded" polynuclear aromatic hydrocarbon. An interesting series of regions of diffuse scattering indicates the presence of a stacking disorder, but in spite of this the molecular dimensions have been determined with considerable precision. The molecule is distorted so that the distance between the overcrowded carbon atoms is 2.95 A, but this separation is achieved with little variation of the valency angles from 120, and this probably explains the retention of aromatic character in spite of the severe distortion. Part IV is an account of the determination of the structures of diindenyl iron and diindenyl cobalt. The "sandwich" nature of these molecules is well illustrated in the projections along two crystal axes. The aromatic rings in these molecules are probably rotating freely in solution and in the vapour state, but fixed in the crystal, and it has been postulated that the configuration is probably trans. While the present analysis has not yielded accurate molecular dimensions (a three-dimensional analysis will be required), It does show definitely that the molecular configuration in the crystal is not trans, but gauche.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Physical chemistry, Molecular chemistry, Organic chemistry
Date of Award: 1957
Depositing User: Enlighten Team
Unique ID: glathesis:1957-79212
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 31 Mar 2020 09:09
Last Modified: 31 Mar 2020 09:09

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