Polarographic and electrochemical studies of some aromatic and heterocyclic nitro compounds. Part III: Electroreduction of mono- and dinitropyrazoles and -imidazoles was written by Dumanovic, D.;Jovanovic, J.;Suznjevic, D.;Erceg, M.;Zuman, P.. And the article was included in Electroanalysis in 1992.Product Details of 54210-32-1 This article mentions the following:
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 4-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 2nd hydrogen ion probably involved in protonation of the heterocyclic ring. This 2nd proton is for nitroimidazoles transferred before the uptake of the 1st electron, for nitropyrazoles probably after this uptake. The transfer of the 2nd electron is the potential determining step. The 2 sequences are H+, H+, e, H+, e, 2e, H+ and H+, e, H+, H+, e, 2e, H+, resp. For nitropyrazoles and nitroimidazoles without an alkyl substituent on the ring N, 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 1st 4-electron step undergoes a base catalyzed dehydration yielding a quinone-like ketimine. Easy reduction of this species results in alk. solutions in a limiting current which is significantly higher than corresponds to a 4-electron and limits to a 6-electron reduction Such dehydration reactions occur considerably faster for dihydroxylamino derivatives formed in the reduction of dinitropyrazoles resulting in 2 waves with total transfer of up to 12 electrons. In the experiment, the researchers used many compounds, for example, 1-Methyl-3-nitro-1H-pyrazole (cas: 54210-32-1Product Details of 54210-32-1).
1-Methyl-3-nitro-1H-pyrazole (cas: 54210-32-1) belongs to pyrazole derivatives. Pyrazole has two ring nitrogen atoms in which N1 is pyrrolic and N2 is pyridine-like. The N1 nitrogen is not reactive but is deprotonated in the presence of a base-forming anion. The presence of both electronegative nitrogen atoms in the pyrazole ring reduces the electron density of the C3- and C5-positions leaving electron density of C4-position unaltered. Thus the C4-position is vulnerable to electrophilic attack. The C3 electrophilic-position may undergo deprotonation in the presence of a strong base leading to ring opening.Product Details of 54210-32-1
Referemce:
Pyrazole – Wikipedia,
Pyrazoles – an overview | ScienceDirect Topics