“…The second reduction wave corresponds to the one electron reduction of Q-O − to Q-O •= . However, there is some controversy with regard to the electrochemical reduction of the conjugate base formed from such hydroxy quinones [156][157][158][159][160][161].…”
Section: Influence Of Hydrogen Bonding Acidic and Basic Additives Omentioning
confidence: 99%
“…To control the coupled chemical reaction in one case methylation of the -OH group (APZms) was done while in another addition of a strong base, tetramethylammonium phenolate (Me 4 N + C 6 H 5 O − ) completely deprotonated the APZs. In both cases there was a recovery of the reversible character of Q/Q [161]. To control self-protonation reactions mentioned above from occurring during electrochemical reduction of PQOH, weak acids such as benzoic acid and a strong acid such as perchloric acid were used as acid additives while a weak base sodium benzoate and a strong base tetraethylammonium phenolate were used as basic additives.…”
Section: Influence Of Hydrogen Bonding Acidic and Basic Additives Omentioning
The electron transfer reactions involving quinones, hydroquinones, and catechols are very important in many areas of chemistry, especially in biological systems. The therapeutic efficiency as well as toxicity of anthracycline anticancer drugs, a class of anthraquinones, is governed by their electrochemical properties. Other quinones serve as important functional moiety in various biological systems like electron-proton carriers in the respiratory chain and their involvement in photosynthetic electron flow systems. The present paper summarizes literatures on the reduction of quinones in different solvents under various conditions using different electrochemical methods. The influence of different reaction conditions including pH of the media, nature of supporting electrolytes, nature of other additives, intramolecular or intermolecular hydrogen bonding, ion pair formation, polarity of the solvents, stabilization of the semiquinone and quinone dianion, catalytic property, and adsorption at the electrode surface, are discussed and relationships between reaction conditions and products formed have been presented.
“…The second reduction wave corresponds to the one electron reduction of Q-O − to Q-O •= . However, there is some controversy with regard to the electrochemical reduction of the conjugate base formed from such hydroxy quinones [156][157][158][159][160][161].…”
Section: Influence Of Hydrogen Bonding Acidic and Basic Additives Omentioning
confidence: 99%
“…To control the coupled chemical reaction in one case methylation of the -OH group (APZms) was done while in another addition of a strong base, tetramethylammonium phenolate (Me 4 N + C 6 H 5 O − ) completely deprotonated the APZs. In both cases there was a recovery of the reversible character of Q/Q [161]. To control self-protonation reactions mentioned above from occurring during electrochemical reduction of PQOH, weak acids such as benzoic acid and a strong acid such as perchloric acid were used as acid additives while a weak base sodium benzoate and a strong base tetraethylammonium phenolate were used as basic additives.…”
Section: Influence Of Hydrogen Bonding Acidic and Basic Additives Omentioning
The electron transfer reactions involving quinones, hydroquinones, and catechols are very important in many areas of chemistry, especially in biological systems. The therapeutic efficiency as well as toxicity of anthracycline anticancer drugs, a class of anthraquinones, is governed by their electrochemical properties. Other quinones serve as important functional moiety in various biological systems like electron-proton carriers in the respiratory chain and their involvement in photosynthetic electron flow systems. The present paper summarizes literatures on the reduction of quinones in different solvents under various conditions using different electrochemical methods. The influence of different reaction conditions including pH of the media, nature of supporting electrolytes, nature of other additives, intramolecular or intermolecular hydrogen bonding, ion pair formation, polarity of the solvents, stabilization of the semiquinone and quinone dianion, catalytic property, and adsorption at the electrode surface, are discussed and relationships between reaction conditions and products formed have been presented.
“…When the scan rate increases, the oxidation current signal II a ‘ ‘ diminishes until it disappears (Figure B and C). It is important to note that in most of the studies reported up to date, the voltammetric analysis is restricted to the potential window where the first reduction peak appears. ,, …”
Section: Resultsmentioning
confidence: 99%
“…An interesting alternative to stabilize the nitro anion radical is to change the acidity of the phenolic proton in a given nitrophenol derivative. In the case of substituted 2-nitrophenols, this can be achieved by modifying the chemical nature of a substituent group in the molecule, which can add or withdraw electronic density to the hydroxy moiety; the substituent effect changes the acidity of the molecule in a similar way as has been studied in α-OH quinones, , modifying the reduction pathway, which would be particularly important for stabilizing an anion radical structure. 1 Structures of the 4-R-2-nitrophenol derivatives studied in this work.…”
A voltammetric and spectroelectrochemical ESR study of the reduction processes of five substituted 4-R-2nitrophenols (R ) -H, -OCH 3 , -CH 3 , -CN, -CF 3 ) in acetonitrile was performed. In the potential range considered here (-0.2 to -2.5 V vs Fc + /Fc), two reduction signals (I c and II c ) were detected; the first one was associated with the formation of the corresponding hydroxylamine via a self-protonation pathway. The voltammetric analysis at the first reduction signal showed that there are differences in the reduction pathway for each substituted 4-R-2-nitrophenol, being the E 1/2 values determined by the inductive effect of the substituent in the meta position with respect to the nitro group, while the electron-transfer kinetics was determined by the protonation rate (k 1 + ) of the anion radical electrogenerated. However, at potential values near the first reduction peak, no ESR signal was recorded from stable radical species, indicating the instability of the radical species in solution. Nevertheless, an intense ESR spectrum generated at the second reduction peak was detected for all compounds, indicating the monoelectronic reduction of the corresponding deprotonated 4-R-2-nitrophenols. The spin-coupling hyperfine structures revealed differences in the chemical nature of the electrogenerated radical; meanwhile, the -CF 3 and -CN substituents induced the formation of a dianion radical structure, and the -H, -CH 3 , and -OCH 3 substituents provoked the formation of an anion radical structure due to protonation by acetonitrile molecules of the initially electrogenerated dianion radical. This behavior was confirmed by analyzing the ESR spectra in deuterated acetonitrile and by performing quantum chemical calculations of the spin densities at each site of the electrogenerated anionic radicals.
“…Man has also found a number of uses for quinones, such as dyes and as oxidizing and reducing agents in industrial and laboratory scale chemical synthesis. In addition, a number of quinones have also been found to have medicinal properties, including antibiotic, antimicrobial, and anticancer activity. , Quinone compounds are widely distributed chemical groups in nature which play several different roles in living organisms, − and hydroxyquinones are of significant interest owing to their important biological functions.…”
The electrolysis of 1,8-Dihydroxy-9,10-Anthracenedione (Q) has been done in an H-shaped electrolytic cell. The electrolytic products were characterized by microscope, IR, MS and NMR.As the crystal is too small to get a single crystal on the surface of the Pt electrode, the X-ray single crystal diffraction can not be used to test it.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
