Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.475799
Title: Synthesis of sulphones : interactions of sulphuric acid and sulphonic acids with trifluoroacetic acid anhydride
Author: Tyobeka, Themba E.
Awarding Body: University of London
Current Institution: Royal Holloway, University of London
Date of Award: 1979
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Abstract:
Some diaryl sulphones have been prepared by the reaction of p-toluene sulphonic acid with aromatic hydrocarbons in the presence of trifluoroacetic anhydride. The various isomeric products were separated by g. l. c., the major isomers isolated by fractional recrystallisation and their structures confirmed using various spectroscopic techniques. The kinetics of the interactions between trifluoroacetic anhydride and the sulphonic acids (methane sulphonic and mesitylene sulphonic acid) have been studied and these results used to propose a mechanism for the trifluoroacetic anhydride 'catalysed' formation of sulphones in the reaction of p-toluene sulphonic acid with aromatic hydrocarbons in nitromethane. This mechanism involves the formation of an intermediate (p-toluene sulphonyl trifluoroacetate) which ionises into p-toluene sulphonylium and trifluoroacetate ions. Electrophilic attack by the sulphonylium ions on the aromatic hydrocarbon results in the formation of sulphones. Symmetrical diaryl sulphones have been prepared from the reaction of sulphuric acid with aromatic hydrocarbons using trifluoroacetic anhydride. The major isomers were isolated and identified. Unsymmetrical diaryl sulphones have also been prepared by a similar method by the sequential addition of two different aromatic hydrocarbons to solutions of trifluoroacetic anhydride and sulphuric acid in nitromethane. The isomeric products formed in both these reactions were separated by g.l.c. The interactions of trifluoroacetic anhydride and sulphuric acid in various mixtures of dichloro-methane and nitromethane were studied and the results again utilised to propose the mechanisms for the reactions ofsulphuric acid with aromatic hydrocarbons in the presence of trifluoroacetic anhydride. This mechanism involves the formation of first a monoanhydride (trifluoroacetyl sulphuric acid) which reacts further to give the dianhydride [di-(trifluoroacetyl) sulphate]. The dianhydride gives rise to an initial regiospecific electrophilic attack upon the aromatic hydrocarbon to form the aryl sulphonyl trifluoro-acetate. The aryl sulphonyl trifluoroacetate then reacts with the second aromatic hydrocarbon to give sulphones with the normal pattern of electrophilic substitution. Symmetrical diaryl sulphones have also been prepared from the reaction of aromatic hydrocarbons with hydroxylamine-O-sulphonic and trifluoroacetic anhydride and the mechanism of this reaction proposed on the basis of the above reactions.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.475799  DOI: Not available
Keywords: Organic Chemistry
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