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Title: Selectivity in aqueous mixtures
Author: Jones, R. O.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1995
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Selectivity data were obtained for solvolyses for p-nitrobenzoyl and p-nitrobenzenesulphonyl chlorides in aqueous methanol and ethanol at 25oC by HPLC analysis of the solvolysis mixtures. Kinetic data were also obtained for p-nitrobenzoyl chloride in aqueous methanol and ethanol mixtures and water. Selectivity data for p-nitrobenzenesulphonyl chloride was collected after one half life to limit decomposition of the ester product using a refrigerated HPLC system to avoid decomposition of p-nitrobenzenesulphonyl chloride to p-nitrobenzenesulphonic acid on the HPLC column. The experimental data was used to test two rate-product correlations derived from a third over kinetic model. Calculated and observed rate constants agreed well providing excellent support for the third order kinetic model. The second part of this thesis is a study of alkylation of 2-amino-6-methyl-5-oxo-4,5-dihydro-5-triazole-[1,5z]pyrimidine (known as precursor) to give the N-alkyl product 2-amino-6-methyl-5-oxo-4-(n-propyl)-4,5-dihydro-5-triazole-[1,5a]pyrimidine. The process was studied under a wide variety of conditions in the presence of tetrabutylammonium bromide with alkali metal bases in water, using propyl bromide as alkylating agent to maximise yield and study the reaction mechanism. Selectivity of benzyl bromide between precursor and hydroxide was used as a mechanistic probe to see if tetrabutylammonium bromide enhanced alkylation rates, and also as a mechanistic probe to study the reaction pathway. Other mechanistic probes were used to deduce if the reaction proceeded via a phase transfer pathway, or an aqueous homogeneous mechanism. The results showed that the process was aqueous homogeneous in nature.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available