Electrochemical characteristics of nitro-heterocyclic compounds of biological interest. IV. Lifetime of the metronidazole radical anion.
Electrochemical studies on metronidazole using mixed aqueous/dimethylformamide (DMF) solvents have allowed us to generate the one-electron addition product, the nitro radical anion, RNO2(-.). Cyclic volt-ammetric techniques have been employed to study the tendency of RNO2-.to undergo further chemical reaction. The return-to-forward peak current ratio, ipr/ipf, was found to increase towards unity with increasing DMF content of the medium, indicating the extended lifetime of RNO2(-.). Second order kinetics for the decay of RNO2-were established at all DMF concentrations examined. Extrapolation has allowed the rate constant and a first half-life of 8.4 x 10(4) dm3/mol-sec and 0.059 seconds respectively, to be determined for the decay of RNO2-in a purely aqueous media. This is impossible by direct electrochemical measurement in water, due to a different reduction mechanism, giving the hydroxylamine derivative in a single 4-electron step. The application of the technique to other nitro-aromatic compounds is discussed.
Tocher
J H
JH
Chemotherapy Research Unit, North East London Polytechnic.
Edwards
D I
DI
D004355:Drug Stability; D004563:Electrochemistry / Q000379:methods; D005609:Free Radicals; D007700:Kinetics; D008795:Metronidazole
D005609:Free Radicals; D008795:Metronidazole