Polarographic and electrochemical studies of some aromatic and heterocyclic nitro compounds, part III: Electroreduction of mono‐ and dinitropyrazoles and ‐imidazoles
Samo za registrovane korisnike
1992
Članak u časopisu (Objavljena verzija)
Metapodaci
Prikaz svih podataka o dokumentuApstrakt
The reduction of mono‐ and dinitropyrazoles and of nitroimidazoles follows the general pattern of reduction of aromatic nitro compounds: The nitro group is reduced in a four‐electron step to a hydroxylamino group and the protonated form of the hydroxylamino group is—in the lower pH range—further reduced to an amine. This reduction differs from that of nitrobenzenes in participation of a second hydrogen ion probably involved in protonation of the heterocyclic ring. This second proton is for nitroimidazoles transferred before the uptake of the first electron, for nitropyrazoles probably after this uptake. The transfer of the second electron is indicated to be the potential determining step. The two sequences are H+, H+, e, H+, e, 2e, H+ and H+, e, H+, H+, e, 2e, H+, respectively. For nitropyrazoles and nitroimidazoles without an alkyl substituent on the ring nitrogen, the reduction process is further complicated by the dissociation of the NH‐group in the heterocyclic ring. For 1‐alkyl‐5‐...nitroimidazoles, for 4(5)‐nitroimidazole and for N‐unsubstituted‐4‐ and 3(5)‐ nitropyrazoles (but not for 2‐nitroimidazoles, 1‐alkyl‐4‐nitroimidazoles and 1‐alkylnitropyrazoles) the hydroxylamino derivative formed in the first four‐electron step undergoes a base catalyzed dehydration yielding a quinone‐like ketimine. Easy reduction of this species results in alkaline solutions in a limiting current which is significantly higher than corresponds to a four‐electron and limits to a six‐electron reduction. Such dehydration reactions occur considerably faster for dihydroxylamino derivatives formed in the reduction of dinitropyrazoles resulting in two waves with total transfer of up to 12 electrons.
Ključne reči:
Reduction Mechanism / Polarography / Nitropyrazoles / NitroimidazolesIzvor:
Electroanalysis, 1992, 4, 9, 871-887Institucija/grupa
Institut za opštu i fizičku hemijuTY - JOUR AU - Dumanović, D AU - Jovanović, J AU - Sužnjević, Desanka AU - Erceg, M AU - Zuman, P PY - 1992 UR - https://riofh.iofh.bg.ac.rs/handle/123456789/17 AB - The reduction of mono‐ and dinitropyrazoles and of nitroimidazoles follows the general pattern of reduction of aromatic nitro compounds: The nitro group is reduced in a four‐electron step to a hydroxylamino group and the protonated form of the hydroxylamino group is—in the lower pH range—further reduced to an amine. This reduction differs from that of nitrobenzenes in participation of a second hydrogen ion probably involved in protonation of the heterocyclic ring. This second proton is for nitroimidazoles transferred before the uptake of the first electron, for nitropyrazoles probably after this uptake. The transfer of the second electron is indicated to be the potential determining step. The two sequences are H+, H+, e, H+, e, 2e, H+ and H+, e, H+, H+, e, 2e, H+, respectively. For nitropyrazoles and nitroimidazoles without an alkyl substituent on the ring nitrogen, the reduction process is further complicated by the dissociation of the NH‐group in the heterocyclic ring. For 1‐alkyl‐5‐nitroimidazoles, for 4(5)‐nitroimidazole and for N‐unsubstituted‐4‐ and 3(5)‐ nitropyrazoles (but not for 2‐nitroimidazoles, 1‐alkyl‐4‐nitroimidazoles and 1‐alkylnitropyrazoles) the hydroxylamino derivative formed in the first four‐electron step undergoes a base catalyzed dehydration yielding a quinone‐like ketimine. Easy reduction of this species results in alkaline solutions in a limiting current which is significantly higher than corresponds to a four‐electron and limits to a six‐electron reduction. Such dehydration reactions occur considerably faster for dihydroxylamino derivatives formed in the reduction of dinitropyrazoles resulting in two waves with total transfer of up to 12 electrons. T2 - Electroanalysis T1 - Polarographic and electrochemical studies of some aromatic and heterocyclic nitro compounds, part III: Electroreduction of mono‐ and dinitropyrazoles and ‐imidazoles EP - 887 IS - 9 SP - 871 VL - 4 DO - 10.1002/elan.1140040908 UR - conv_1337 ER -
@article{ author = "Dumanović, D and Jovanović, J and Sužnjević, Desanka and Erceg, M and Zuman, P", year = "1992", abstract = "The reduction of mono‐ and dinitropyrazoles and of nitroimidazoles follows the general pattern of reduction of aromatic nitro compounds: The nitro group is reduced in a four‐electron step to a hydroxylamino group and the protonated form of the hydroxylamino group is—in the lower pH range—further reduced to an amine. This reduction differs from that of nitrobenzenes in participation of a second hydrogen ion probably involved in protonation of the heterocyclic ring. This second proton is for nitroimidazoles transferred before the uptake of the first electron, for nitropyrazoles probably after this uptake. The transfer of the second electron is indicated to be the potential determining step. The two sequences are H+, H+, e, H+, e, 2e, H+ and H+, e, H+, H+, e, 2e, H+, respectively. For nitropyrazoles and nitroimidazoles without an alkyl substituent on the ring nitrogen, the reduction process is further complicated by the dissociation of the NH‐group in the heterocyclic ring. For 1‐alkyl‐5‐nitroimidazoles, for 4(5)‐nitroimidazole and for N‐unsubstituted‐4‐ and 3(5)‐ nitropyrazoles (but not for 2‐nitroimidazoles, 1‐alkyl‐4‐nitroimidazoles and 1‐alkylnitropyrazoles) the hydroxylamino derivative formed in the first four‐electron step undergoes a base catalyzed dehydration yielding a quinone‐like ketimine. Easy reduction of this species results in alkaline solutions in a limiting current which is significantly higher than corresponds to a four‐electron and limits to a six‐electron reduction. Such dehydration reactions occur considerably faster for dihydroxylamino derivatives formed in the reduction of dinitropyrazoles resulting in two waves with total transfer of up to 12 electrons.", journal = "Electroanalysis", title = "Polarographic and electrochemical studies of some aromatic and heterocyclic nitro compounds, part III: Electroreduction of mono‐ and dinitropyrazoles and ‐imidazoles", pages = "887-871", number = "9", volume = "4", doi = "10.1002/elan.1140040908", url = "conv_1337" }
Dumanović, D., Jovanović, J., Sužnjević, D., Erceg, M.,& Zuman, P.. (1992). Polarographic and electrochemical studies of some aromatic and heterocyclic nitro compounds, part III: Electroreduction of mono‐ and dinitropyrazoles and ‐imidazoles. in Electroanalysis, 4(9), 871-887. https://doi.org/10.1002/elan.1140040908 conv_1337
Dumanović D, Jovanović J, Sužnjević D, Erceg M, Zuman P. Polarographic and electrochemical studies of some aromatic and heterocyclic nitro compounds, part III: Electroreduction of mono‐ and dinitropyrazoles and ‐imidazoles. in Electroanalysis. 1992;4(9):871-887. doi:10.1002/elan.1140040908 conv_1337 .
Dumanović, D, Jovanović, J, Sužnjević, Desanka, Erceg, M, Zuman, P, "Polarographic and electrochemical studies of some aromatic and heterocyclic nitro compounds, part III: Electroreduction of mono‐ and dinitropyrazoles and ‐imidazoles" in Electroanalysis, 4, no. 9 (1992):871-887, https://doi.org/10.1002/elan.1140040908 ., conv_1337 .