Redox reactions of organic compounds

The redox reactions of organic compounds are influenced by the acid-base properties of the solvents. In protic solvents like water, many organic compounds (Q °) are reduced by a one-step two-electron process, Q°+2H+ + 2e = QH2, although... 

Nucleophilic-electrophilic mechanisms of organic transformations are considered together with redox reactions of organic compounds in order to illustrate common chemical properties of these reactions. 

TTie principle of jAase-transfer reactions — advant eously used for substitution, alkylation, acylation, elimination, and redox reactions of organic compounds, RQ, — is the transfer of an ion from aqueous solution into an apolar phase where the... 

ACs were also modified by treatment by 2-nitro-l-naphthol to manufacture composite supercapacitor electrodes, in which EDL capacitance and pseudocapacitance of the following redox reactions of organic compounds is used o-aminonaphthol o-naphthaquinoneimine (Leitner et al., 2004) ... 

The aspects and applications concerning the redox reactions of organic compounds at BDD electrodes were reviewed recently,and also by our group. Further, reviews on general electrochemical properties and surface... 

Redox reactions of chemical compounds (donor-ac-Donor organic compounds acceptor 02... 

Low-coordinated transition-metal ions acting as active sites both in catalytic redox reactions of organic and inorganic compounds and in coordination-type catalysis. 

One can then attempt to relate the free energy of the reaction (or the equilibrium constant or the redox potential) of the one-electron step to the rate of the reaction. Extensive tabulations of one-electron redox potentials have recently become available (e.g., Wardman, 1989). Often it is possible to relate rate constants to free energy parameters (AG , K, pe°) in a series of related redox reactions (e.g., oxidation of ions of transition elements with O2, H2O2, Mn02, etc.) or redox reactions involving organic compounds with var-... 

Kinetic studies of redox properties of organic compounds in the presence of metal complexes can assist in understanding electron transfer mechanisms in organic molecules. N-substituted phenothiazines are important in biochemistry and pharmacology. The kinetic and equilibrium parameters for a series of phenothiazines in electron transfer reactions with hexaaquairon(III) were established reliably about 25 years ago. [138]... 

A number of Ir(lll)-, Ru(lll)- and Os(VIII)-catalysed redox studies of organic compounds by alkaline hcf are reported. The rates of Ir(III)-catalysed oxidations of arginine and lysine show Michaelis-Menten dependence in amino acids and increase with ionic strength the proposed mechanism assumes the formation of an lr(IIl)-amino acid complex. This study was also published by the authors in another journal. The Ir(in)-catalysed alkaline oxidation of OL-methionine (met) by hcf to methionine sulfone is fractional order in met. The reaction rates increase with increase in OH coneentration. The active species of oxidant and catalyst are [FeCCN) ] and [IrClgCHjOljOH]", respectively. The results of the uncatalysed oxidation of DL-methionine (met) are similar to those of the catalysed reaction. 

The reactions of compounds of the nonmetals are less easy to classify straightforwardly under the heading of substitution reactions than are the reactions of metal complexes. Accordingly there will be some discussion of the redox reactions of these compounds, although those involving a transition metal coreactant will usually not be included. In some cases there will be an overlap with topics usually regarded to be the province of the organic chemist. 

In the present chapter we want to look at certain electrochemical redox reactions occurring at inert electrodes not involved in the reactions stoichiometrically. The reactions to be considered are the change of charge of ions in an electrolyte solution, the evolution and ionization of hydrogen, oxygen, and chlorine, the oxidation and reduction of organic compounds, and the like. The rates of these reactions, often also their direction, depend on the catalytic properties of the electrode employed (discussed in greater detail in Chapter 28). It is for this reason that these reactions are sometimes called electrocatalytic. For each of the examples, we point out its practical value at present and in the future and provide certain kinetic and mechanistic details. Some catalytic features are also discussed. 

One-electron reduction or oxidation of organic compounds provides a useful method for the generation of anion radicals or cation radicals, respectively. These methods are used as key processes in radical reactions. Redox properties of transition metals can be utilized for the efficient one-electron reduction or oxidation (Scheme 1). In particular, the redox function of early transition metals including titanium, vanadium, and manganese has been of synthetic potential from this point of view [1-8]. The synthetic limitation exists in the use of a stoichiometric or excess amount of metallic reductants or oxidants to complete the reaction. Generally, the construction of a catalytic redox cycle for one-electron reduction is difficult to achieve. A catalytic system should be constructed to avoid the use of such amounts of expensive and/or toxic metallic reagents. 

Back electron transfer takes place from the electrogenerated reduc-tant to the oxidant near the electrode surface. At a sufficient potential difference this annihilation leads to the formation of excited ( ) products which may emit light (eel) or react "photochemical ly" without light (1,16). Redox pairs of limited stability can be investigated by ac electrolysis. The frequency of the ac current must be adjusted to the lifetime of the more labile redox partner. Many organic compounds have been shown to undergo eel (17-19). Much less is known about transition metal complexes despite the fact that they participate in fljjany redox reactions. 

---