A Critical Investigation of Methods of Preparing Monohydric Phenols and Derivatives Therefrom

Love, Thomas (1934) A Critical Investigation of Methods of Preparing Monohydric Phenols and Derivatives Therefrom. PhD thesis, University of Glasgow.

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The work described in the following pages was initially intended as a sequel to Professor Gray's investigation of Scottish Shale Oil phenols and as a corollary to the work of my predecessor in the Ferguson Fellowship who investigated the antiseptic properties of mixtures of phenols from different sources. When this work was commenced there was very little known about mono-hydric phenols other than the cresols and xylenols and the number of known derivatives of these phenols which might have been useful as a means of separation was small. Therefore, after having conducted some preliminary work on the phenols derived from Scottish Shale oil and having attempted to isolate individual members, it became evident that, without more definite information about the higher homologues of phenol, any attempted separation would be a complicated process, the success of which would be doubtful. Accordingly the preparation of phenol homologues was undertaken. Phenols have been prepared by two general methods; from hydroxy-aldehydes and ketones and from amines. The main portion of the work has therefore been devoted to the preparation of the intermediates. Individual xylidines have been separated from a mixture, and o- and p-amino-ethyl benzene have been prepared directly from ethyl benzene. Ring methylation of xylidines has been used to prepare mesidine and pseudo-cumidine. The hydroxy-ketones have been prepared by the Fries reaction. Certain abnormalities in this method have become apparent in the course of the present work but no fundamental investigation of the reaction mechanism has been attempted as the present intention was to prepare the hydroxy-ketones. Both Gattermann and Reimer-Tiemann synthesis of hydroxy-aldehydes have been conducted and it has been shown that the Gattermann reaction, which, until recently, has been considered to give exclusively p-hydroxy-aldehydes gives also o-substituted products. Thus from m-cresol all three theoretically possible hydroxy-aldehydes have been isolated. An inaccuracy in the published description of the anil of one of these hydroxy-aldehydes has also been indicated. Both the hydroxy-aldehydes and ketones have been subjected to Clemmensen reduction and by this means the corresponding phenols have been obtained. The Clemmensen reduction has been shown to be ineffective In the case of m-hydroxy-acetophenone and, while It is felt that this is due to some extent to the orientation of the molecule and in particular to the o-p-directing properties of the hydroxyl group, these points have not been followed up as it was considered that such an investigation was outwlth the scope of the present work. Thus m-substituted phenols which could have been prepared in a round about way from the corresponding p-substituted phenols are not included in the phenols here investigated. Derivatives of the prepared phenols have been made and while a number of these derivatives were already known some of them, such as the p-nitro-benzoates, 3:5-dinitro-benzoates and phenoxy-acetate of the ethyl and ethyl-methyl phenols, have been described since this work was commenced. In other cases the derivatives are new. The value of the present work on these derivatives is considered to be the determination and comparison of the solubilities. The solubilities given, while only rough approximations, are sufficiently accurate to indicate any possibilities of easy means of separation by fractional crystallisation. The p-nitro-benzoates and 3:5-dinitro-benzoates have been shown to be useless as a means of separating mono-hydric phenols from a mixture. The phenoxy-acetates allow of a rough separation of o- and p-substituted phenols being made. By the use of phenoxy-acetates a reasonably complete separation of the cresols can be made but these derivatives are not so satisfactory for the separation of the higher homologues.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1934
Depositing User: Enlighten Team
Unique ID: glathesis:1934-79971
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 03 Mar 2020 10:15
Last Modified: 03 Mar 2020 10:15
URI: https://theses.gla.ac.uk/id/eprint/79971

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