Reduction product, 1-electron

The protonated 1-electron reduction product of NO, HNO, also kuowu as uitroxyl, also biuds to heme centers Farmer and coworkers have characterized the reaction of myoglobin(Fe )-NO with Cr in the presence of H+ to produce myoglobiu(Fe )UNO and Cr ... 

Probable Oxidation Processes for 1-Electron Reduction Product... 

Apart from the nuclear bromination observed (Section 2.15.13.1) in the attempted radical bromination of a side-chain methyl group leading to (396), which may or may not have involved radical intermediates, the only other reaction of interest in this section is a light-induced reduction of certain hydroxypyrido[3,4-f)]pyrazines or their 0x0 tautomers analogous to that well-known in the pteridine field (63JCS5156). Related one-electron reduction products of laser photolysis experiments with 1 -deazaflavins have been described (79MI21502). 

In the same year, Evans and coworkers reported the electrochemical reduction of protons to H2 catalyzed by the sulfur-bridged dinuclear iron complex 25 as a hydrogenase mimic in which acetic acid was used as a proton source [201]. The proposed mechanism for this reaction is shown in Scheme 60. The reduction of 25 readily affords 25 via a one electron reduction product 25. Protonation... 

The adsorption maximum of 496 nm characteristic of one electron reduction product of TQ was not observed. TQH2 in DCE could not be determined because of the distribution of TQH2 to W. 

Solutions of tetrazolium salts, e.g., 53, have been reported to both become colored and bleached under the influence of both UV and visible light. Several workers have attributed this phenomenon to photoreduction to the corresponding formazan (51) and the formation of a fluorescent colorless compound (152) through photooxidation.240- 243 The reduction of 152 under UV or blue light to the intense green radical structure (153) has also been reported (Scheme 21).244 A one-electron reduction product (154) is proposed as a short-lived intermediate in the photoreduction.245... 

The presence of the carbonylated complex [Ni icyclamXCO)]4 during the reaction was clearly demonstrated. This compound results from the three-electron reduction product of... 

Misonidazole [27 l-methoxy-3-(2-nitroimidazol-l-yl)-2-propanol] and the model compound l-methyl-2-nitroimidazole have been used as radiosensitizers in the treatment of certain types of human tumors. One important property of these compounds is that they are more toxic to hypoxic cells than to aerobic cells, indicating that reductive metabolism of the drug is involved in the toxicity. Results of a number of studies suggest that intracellular thiols play a significant role in the hypoxic cell toxicity, and it was found that reduction products formed stable thio ethers with GSH (for literature see References 181-183). The reaction mechanism of thio ether formation has not been fully established. It has been suggested that the 4-electron reduction product was involved in thio ether formation181,184,185, and that the hydroxylamine rather than the nitroso derivative was the reactant. On the other hand, an intermediate nitroso derivative is expected to give a sulfenamide cation (see Scheme 1) which easily allows thio ether formation. 

One-Electron Reduction Product of Tris(2,2 -bipyridine)rhodium(III)... 

The two-electron reduction product of terephthalodinitrile reacts with alkyl halides in liquid ammonia to yield 4-alkylbenzonitriles and 2-alkylterephthalodinitriles. The product ratio strongly depends on the alkyl halide and changes in favour of the ipso product, 4-alkylbenzonitrile, on going from tertiary alkyl to primary and from iodide to chloride. This change is the result of increased contribution of the 5n mechanism relative to the ET mechanism. 

A detailed study of the electronic, vibrational, and e.s.r. spectra of a series of substituted dipyrromethane complexes of nickel(ii) has been reported." The reduction of the nickel(ii) 1,19-diethoxycarbonyltetradehydrocorrin cation with a sodium film in THF under high vacuum gives both one- and two-electron reduction products. The one-electron reduction product is a very stable free radical, and the other product is formulated as a Ni" species with the two extra electrons located in ligand n-orbitals. The structures of nickel-(ii)-octaethylporphin and nickel(ii)-deoxophylloerythrin methyl ester-1,2-... 

The bis-hydroxylamine adduct [Fe (tpp)(NH20H)2] is stable at low temperatures, but decomposes to [Fe(tpp)(NO)] at room temperature. [Fe(porphyrin)(NO)] complexes can undergo one-and two-electron reduction the nature of the one-electron reduction product has been established by visible and resonance Raman spectroscopy. Reduction of [Fe(porphyrin)(NO)] complexes in the presence of phenols provides model systems for nitrite reductase conversion of coordinated nitrosyl to ammonia (assimilatory nitrite reduction), while further relevant information is available from the chemistry of [Fe (porphyrin)(N03)]. Iron porphyrin complexes with up to eight nitro substituents have been prepared and shown to catalyze oxidation of hydrocarbons by hydrogen peroxide and the hydroxylation of alkoxybenzenes. ... 

In Sch. 1, if the 002 radical anion reacts with CO2 in solution, CO is formed via a dimeric intermediate in which a C—O bond is formed. A second electron transfer to this intermediate from either the electrode or 002 leads to the formation of carhon monoxide. The ultimate result of this pathway is the formation of the two-electron reduction product, carbon monoxide, and carbonate. In this reaction, a second CO2 molecule acts as the acceptor of the oxide ion formed in the two-electron reduction of CO2 to CO. Many of the features of these reactions are common to the catalyzed reactions discussed in the following. Because free C02 is not present in the catalyzed two-electron reductions of CO2 to CO, the reduction potentials can be considerably less negative than that required to form CO2-. 

Indeed, other electrocatalytic processes were studied, including the pioneering work on chlorate reduction by the six-electron reduction product of 12-molybdophosphate in water-dioxane solutions [169]. This process, extended to bromate, has become a classical test of the electrocatalytic abilities of several POMs [see Table 13]. 

Although the isotope experiments of Goretski and Hollocher (1990) with Paracoccus denitrificans were not exactly trapping experiments, the fact that [ Njnitrite and NO proceeded to N2O via pathways which shared at least one mono-N intermediate in common strongly supported NO as a free intermediate. Because NO and N2O represent 1- and 2-electron reduction products of nitrite, it is inescapable that NO must itself be the common intermediate. 

Reaction (26) is followed by a first order process, which has been interpreted as an homolytic splitting of the N-S bond, Eq. (27), with formation of the one-electron reduction product of NP, [Fe(CN)sNO]3, ... 

Other acceptors which have reduction potentials below the conduction band edge of the illuminated semiconductor can also function in this role. The single electron reduction product derived from methyl viologen, for example, can be detected spectroscopically when a colloidal suspension of titanium dioxide is flashed in the presence of this electron acceptor, Eq. (2)... 

Dioxotetrahydropteridines are reduced analogously400 to the 2,3-di-oxoquinoxalines a reduction scheme was proposed in Part I and substantiated later.401 The primary two-electron reduction product is an enediol that isomerizes to a hydroxycarbonyl compound. After loss of water, the double bond is saturated with the uptake of two electrons and protons and a monooxytetrahydropyrazine ring is formed. 

For the dimer, polographic results in CH3CN reveal a four-membered series (Eq. 32), and the one-electron reduction product was isolated (434). 

At the same time, dimerization of one-electron reduction product was indicated by oscillopolarographic studies in acid for l-R-3,4-diphenyl-6,7-dimethoxybenzo[c]pyrylium perchlorates (R = Me, Et, Ph) (76MI1). As was noted in Section III,F, 1, the benzo[c]pyrylium cation 261, unsubstituted in position 1, undergoes l, 1 -dimerization via the postulated intermediate radical, and the bisisochromene 263 thus formed is readily converted into the initial monomeric salt, but not into the corresponding biscation on treatment with chemical electron acceptors (76KGS999). 

Neither the drug itself nor its two-electron reduction product SR 4317 are toxic as long as the cell is oxygenated [reactions (68) and (71)]. 

The oxidation of alcohols to aldehydes, ketones or carboxylic acids is one of the commonest reactions in organic chemistry, and is frequently achieved by transition metal complexes or salts. However, in most cases the precise mechanisms are not known, and the intermediates not fully characterised. In general, metal complexes of the alcohols are formed as transient intermediates in these reactions, but we shall not deal with these extremely important reactions in any great detail. The precise mechanisms depend upon the accessibility of the various one- and two-electron reduction products of the particular metal ion which is involved in the reaction. However, we will outline a brief indication of the mechanism. The first step involves the formation of an alcohol complex of the metal ion (Fig. 9-14). This might or might not deprotonate to the alkoxide form, depending upon the pH conditions of the reaction, the pK of the alcohol and the polarising ability of the metal ion. 

---