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Isotopic hydrogen exchange in purines.

Taylor, Spencer Edwin. (1978) Isotopic hydrogen exchange in purines. Doctoral thesis, University of Surrey (United Kingdom)..

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The rates of detritiation of [2-[3]H] imidazole, 1-methyl-[8-[3]H]guanosine, 7-methyl[8-[3]H] guanosine, 1-methyl [8-[3]H] -inosine, [8-[3]H] xanthine, [8-[3]H] xanthosine, [8-[3]H] theophylline, [8-[3]H] theobromine, [8-[3]H] paraxanthine, [8-[3]H] caffeine, [8-[3]H]-adenosine 5'-monophosphate, [8-[3]H]adenosine 3'-monophosphate, [8-[3]H] adenosine 3', 5'-cyclic monophosphate, [8-[3]H] guanosine 5'-monophosphate and [8-[3]H]inosine 5'-monophosphate have been measured as a function of pH at 85°. From the observed pH -rate profiles, information concerning the reactive species has been obtained. The reactions were found to be very sensitive to the various ionized species present within the pH range studied. The results were interpreted in terms of specific hydroxide ion attack on these ionized species; the involvement of zwitterionic forms of these species has also been proposed to account for the observed behaviour. The reaction was found to proceed via carbanion- or ylide-type intermediates which are then protonated by the solvent, regenerating the catalyst and effecting exchange. Theoretical pH - rate profiles have been constructed on the basis of these mechanisms and these are found to agree well with the experimental data. Activation parameters and primary kinetic and solvent isotope effects have been obtained for the reaction of the protonated molecules with hydroxide ion. The values obtained suggest either an extremely product-like transition state or the involvement of "internal-return". Metal ion complexation to the N-7 position of purines has been found to be equivalent to protonation or alkylation and detritiation occurs via a pathway analogous to that of the protonated or alkylated molecules.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors :
Taylor, Spencer Edwin.
Date : 1978
Contributors :
Additional Information : Thesis (Ph.D.)--University of Surrey (United Kingdom), 1978.
Depositing User : EPrints Services
Date Deposited : 22 Jun 2018 14:26
Last Modified : 06 Nov 2018 16:53

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