The role of protonation, hydration, elimination, and ring opening in the electroreduction of hexazinone

Privman, Marina; Zuman, P.

doi:10.1016/s0022-0728(98)00277-0

Cited by 21 publications

(9 citation statements)

References 29 publications

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“…Covalent hydration of this compound most probably involves a nucleophilic addition of water to a CN bond in the pyrimidine ring. Such hydration, manifested by a dip of the limiting current over a certain pH range, has recently been reported for some 2-aminopyrimidines . The lower limiting current of IV (Figure A) may be predominantly attributed to the large difference in molecular weights, resulting in a marked decrease in its diffusion coefficient.…”

Section: Resultssupporting

confidence: 67%

“…Such hydration, manifested by a dip of the limiting current over a certain pH range, has recently been reported for some 2-aminopyrimidines. 30 The lower limiting current of IV (Figure 2A) may be predominantly attributed to the large difference in molecular weights, resulting in a marked decrease in its diffusion coefficient. Limiting currents of ATP corrected for the effects of difference in diffusion coefficients would be by ∼30% higher (as indicated by X symbols in Figure 2A) than measured values, but still indicate an effect of hydration.…”

Section: Resultsmentioning

confidence: 98%

“…The reduction is complicated by a covalent hydration of the pyrimidine ring, similar to that observed for some 2-aminopyrimidines. 30 No reduction of the less protonated forms of I has been observed within the available potential range.…”

Section: Linear Sweep Voltammetry (Lsv)mentioning

confidence: 94%

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Electrochemical Determination of HIV Drug Abacavir Based on Its Reduction

2007

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Abacavir (I), a drug used in the treatment of HIV, is electrochemically reduced at the dropping mercury electrode in a four-electron process, similar to structurally related adenine (III) and adenosine triphosphate (IV). To undergo the reduction, the species is protonated in the vicinity of the electrode. The protonations take place on the 6-amino group and on one of the pyrimidine ring nitrogens. The role of covalent hydration of the pyrymidine ring has been interpreted. Best suited as supporting electrolytes for analytical purposes are solutions of 0.1-1.0 M sulfuric, perchloric, or hydrochloric acids. Procedures of analyses of tablets containing I were established and validated, based on peak currents obtained by linear sweep, differential pulse, or square-wave voltammetry with a hanging mercury drop electrode as indicator electrode. The procedure proved to be more sensitive and more reliable than that based on oxidation on a glassy carbon electrode, proposed previously.

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Section: Resultssupporting

confidence: 67%

Section: Resultsmentioning

confidence: 98%

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Electrochemical Determination of HIV Drug Abacavir Based on Its Reduction

2007

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“…Similar agreement between values of pK a obtained from shifts of half-wave potentials with pH and pK a -values obtained spectrophotometrically has been observed for pesticides hexazinon [15], metamitron(I) [16], and metribuzin [17].…”

Section: Acid-base Equilibriasupporting

confidence: 81%

Role of Mercury Electrodes in Contemporary Analytical Chemistry

Zuman

2000

Electroanalysis

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“…In an early electrochemical study, the reduction potential of the azine system C 6 H 5 -CHN−NCH-C 6 H 5 was reported to be identical to that of the corresponding hydrazone, C 6 H 5 -CH 2 -NH-NCH-C 6 H 5 , suggesting a lack of conjugation in the former − Of their important results, which examine the irreversible reduction of the protonated forms of the azine in protic solvents, one pertinent to this question is illustrated by the reduction of the herbicide metamitron . The first reduction wave of metamitron is coincident with the reduction of 2,3-dihydrometamitron and is thought to involve the reduction of the 1,6-imine bond.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the Extent of Conjugation in Symmetrical and Asymmetrical Aryl-Substituted Acetophenone Azines Using Electrochemical Methods

Sauro

Workentin

2001

J. Org. Chem.

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The electrochemical behavior of a series of symmetrical and unsymmetrical aryl-substituted acetophenone azines (1-X/Y, where X and Y are 4-NO2, 4-CN, H, 3-OCH3, 4-OCH3, 4-CH3, and 4-N(CH3)2) was studied in acetonitrile and N,N-dimethylformamide (DMF) solution using cyclic voltammetry (CV). Compounds 1-X/Y, where neither X or Y are nitro substituents, undergo successive reduction to their radical anion (1-X/Y.-) and then dianion (1-X/Y2-), respectively. In all cases, the formation of the radical anion is completely reversible and the standard reduction potentials, Eo1-X/Y/1-X/Y.- could be determined. The reversibility of the second electron transfer is substituent dependent with certain dianions sufficiently basic to be protonated under our conditions. Standard reduction potentials (Eo1-X/Y/1-X/Y.-) for the formation of radical anions exhibit a large substituent effect with values differing by more than 0.66 V throughout the series going from 1-4-CN/4-CN to 1-4-OCH3/4-OCH3; similar substituent effects were determined for the formation of the dianion. The nitro-containing azines deviate from the above-mentioned behavior. With the exception of 1-4-NO2/4-NO2, they exhibit single electron waves that have values of Eo1-X/Y/1-X/Y.- within 40 mV of each other and thus the reduction is not subject to the same substituent effect as the other azines. 1-4-NO2/4-NO2 exhibits an Eo at a similar potential, but is a two-electron reversible wave with features indicative of a reduction system containing two localized, nonconjugated redox centers. The reduction potentials of all the aryl azines were correlated with Hammett sigma parameters to look at variations in Eo1-X/Y/1-X/Y.- vs SCE as a function of substituent. The small rho values in combination with the other electrochemical data provide support for single bond character of the N-N bond and evidence for a lack of strong electronic communication between the two aryl centers through the azomethine bonds, especially for those systems with electron-withdrawing groups.

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The role of protonation, hydration, elimination, and ring opening in the electroreduction of hexazinone

Cited by 21 publications

References 29 publications

Electrochemical Determination of HIV Drug Abacavir Based on Its Reduction

Electrochemical Determination of HIV Drug Abacavir Based on Its Reduction

Role of Mercury Electrodes in Contemporary Analytical Chemistry

Evaluation of the Extent of Conjugation in Symmetrical and Asymmetrical Aryl-Substituted Acetophenone Azines Using Electrochemical Methods

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