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Title: Catalysis of phosphate ester hydrolysis through hydrogen bonding
Author: Tossell, Katie Jayne
ISNI:       0000 0004 2740 8049
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2011
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This thesis describes the investigation of the effect of hydrogen bonding on the rate of phosphoryl transfer in the reaction of diethyl 8-dimethylamino-I-naphthyl phosphate 3 with a nucleophile. The study of the hydrolysis of triester 3 is in the literature; triester 3 is catalysed by the dimethylammonium general acid, with a rate acceleration of almost 106 in comparison to the hydrolysis of diethyl I-naphthyl phosphate. 58 To ascertain whether the reactivity of triester 3 is specific to this system, the methylation of the amine in triester 3 was altered. Triesters diethyl 8- amino-I-naphthyl phosphate 6 and diethyl 8-methyIamino-l-naphthyl phosphate 7 were synthesised and their reaction with water and hydroxylamine was studied. It is concluded that the effect of methylation of the amine on the rate of P-O cleavage in triester 3 is insignificant, and that the hydrogen bond donor ability of the amino proton donor is not an important factor in increasing the rate of P-O cleavage; the energy of triesters 6H+, 7H+ and 3H+ are very similar. The hydrolysis of 8-dimethylamino-l-naphthyl phosphate 5m is also known to exhibit general acid catalysis by the dimethylammonium group." To ascertain whether the effect of methylation of the amine on the rate of p-o cleavage in monoester 5mis also insignificant, the hydrolysis of 8- rnethylamino-I-naphthyl phosphate 27m was studied. It is concluded that methylation of the amino general acid in triester 6H+ and monoester 5m has no significant effect on the rate of phosphoryl transfer, regardless of the different transition states that are formed. By studying the hydrolysis of monoester 36d it is concluded that the reactivity of monoester 5m is also dependent on the proton donor ability of the amino group. The elimination of various functionalised 8-amino-I-tetralone-3-sulfonic acids with hydroxide has been studied. There is a clear difference between the rates of elimination of the tetralones upon varying the proton donor ability of the amino group. No apparent trend relating the rate of elimination to the proton donor ability of the hydrogen bond donor, or to the pKa of the conjugate acid of the tetralones is observed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available