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Title: Kinetics of oxidation of amino-acids by chloramine-T and related compounds
Author: Salman, Noori Yousif
ISNI:       0000 0001 3547 4394
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 1988
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Studies of the kinetics and mechanism of the oxidation of amino-acids by chloramine-T, bromamine-T, di-chloramine-T, N-chlorosuccinimide and N-bromosuccinimide in the range pH 2-9 at 25 or 30°C in aqueous solution are described in this thesis. The effects of added p-toluenesulphonamide, chloride ion, or bromide ion on the rates have been studied. All the previous work on the chloramine-T oxidations of amino-acids was carried out at either pH 9 and the reactions were followed by iodometric titration. In the present work, UV spectrophotometry was used successfully to follow the reactions of all the above oxidants. Some runs were followed by iodometry for comparison. In general the kinetics of the oxidation by CAT (chloramine-T) with respect to the oxidant were first order ([CAT]=1x10[-4]M) or consecutive first order ([CAT]=3x10[-3]M). At pH's > 3 the oxidations were generally first order with respect to amino-acid, except for the oxidation of valine and arginine which showed Michaelis-Menten kinetics. Below pH 3 there was little dependence on amino-acid concentrations and it is suggested that the active species is HOCl or H[2]OCl[+] formed in a partly rate-determining step from CAT. At high pH's, the dependence of rate on pH suggests that the CAT anion is the active oxidant. Agreement was observed between the rates of the second stages of the oxidations by CAT and N-chlorosuccinimide, suggesting that these oxidations proceed via the same intermediate which is probably the chloroester. Spectroscopic evidence indicates the formation of the imine as another intermediate in the N-chlorosuccinimide reaction. In the oxidations by dichloramine-T the rate constants for the second stage agree with the rate constants for the CAT oxidations ([oxidant]=1.0x10[-4]M). Clearly CAT formed in the first stage oxidises the amino-acid in the second stage. A product analysis of the oxidations of amino-acids by CAT has been carried out by NMR and GLC. Formation of an aldehyde or a nitrile (depending on the conditions) has been confirmed. Improved calculations of the different species present in CAT solutions at various pH's have been carried out.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Physical chemistry