The pyrolisis of some alpha-substituted benzyl esters and related substances

Jones, Edward (1958) The pyrolisis of some alpha-substituted benzyl esters and related substances. PhD thesis, University of Glasgow.

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Abstract

The pyrolysis of esters is exceedingly complex. It is known that most carboxylic esters decompose by two or more concurrent, competitive routes. The various breakdown routes of an ester may be predicted in advance with a fair degree of accuracy, although a novel scission is occasionally observed. Certain atoms and groups have been found to affect the thermal stability of esters and their mode of breakdown. The present work consists of an investigation into the way in which the thermostability of benzyl benzoate is affected by the introduction of different atoms and groups into the benzyl group. Cyano, bromine and benzoyl groups were chosen to represent electrophilic substituents and the phenyl group a nucleophilic substituent. Certain other esters were also examined to facilitate the interpretation of the results obtained. While most of the breakdown routes obtained could be predicted, certain unexpected results were obtained. In the electrophilic substituted series of esters, a novel scission was recorded. This consisted of the formation of a diketone and the elimination of a simple molecule from the parent ester. This new scission has been examined in detail. The nucleophilic substituted esters decomposed in a complex manner giving a variety of products some of which were quite unexpected. The thermal stability of diesters has also been studied and compared with that of other diesters e.g. ethylene dibenzoate, a model compound of poly (ethylene terephthalate), Attempts have been made to prepare a polyester, poly (methylene terephthalate). Although much is known about the classes of ester breakdown little is known about the actual mechanisms involved. Preliminary investigations described in this thesis suggest the existence of charged particles during the pyrolysis of certain esters. An ionic mechanism is tentatively put forward to explain ester breakdown. A second possibility, based on free radicals, is also advanced. Outlines for further work are indicated.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1958
Depositing User: Enlighten Team
Unique ID: glathesis:1958-72522
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 11 Jun 2019 11:06
Last Modified: 11 Jun 2019 11:06
URI: http://theses.gla.ac.uk/id/eprint/72522

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