In:
Canadian Journal of Chemistry, Canadian Science Publishing, Vol. 70, No. 11 ( 1992-11-01), p. 2818-2827
Abstract:
To assign unidentified ESR signals obtained in a Fenton system with a spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), fundamental reactions of DMPO have been thoroughly investigated. When the concentration of Fe 2+ in Fenton systems exceeded 1% of that of DMPO, background ESR signals totally distinguishable from 2-hydroxy-5,5-dimethyl-1-pyrrolidinyloxy (DMPO-OH) appeared, and simultaneously absorbance at 520 nm increased, which was characteristic of hydroxamic acids complexed with Fe 3+ . To prove the postulated formation of hydroxamic acid as a key intermediate, DMPO was subjected to Fenton reaction or was treated with Fe 3+ in aqueous solution to produce DMPO-OH (Makino etal. Biochem. Biophys. Res. Commun. 172, 1073 (1990)), and a major product was isolated by RPLC. Based on 1 H, 13 C NMR and MS measurements, the structure of the major product was assigned to 1-hydroxy-5,5-di-methyl-1-pyrrolid-2-one (HDMPN) having a hydroxamic acid structure. Temperature dependence of NMR spectra and careful analysis of the fragmentation patterns in MS further revealed that HDMPN was present in equilibrium with 2-hydroxy-5,5-dimethyl-1-pyrroline-N-oxide (HDMPO), a tautomer of HDMPN. It has also been shown that the oxidation of DMPO yielding HDMPN and HDMPO occurs via DMPO-OH and is driven by Fe 3+ . These oxidation products (HDMPN and HDMPO) were readily converted to the corresponding ESR visible aminoxyl radicals by oxidation and • OH addition in aqueous solution, respectively, and superimposition of the ESR signals arising from these radicals accounts for the background signals observed in Fenton systems with DMPO as a spin trap.
Type of Medium:
Online Resource
ISSN:
0008-4042
,
1480-3291
Language:
English
Publisher:
Canadian Science Publishing
Publication Date:
1992
detail.hit.zdb_id:
1482256-8
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