Aniline oxidation potential

The nucleophilic reaction with the solvent is of crucial importance. Monomers with lower oxidation potentials (aniline and pyrrole) can easily be polymerized even in aqueous electrolytes. For monomers with higher oxidation potentials, aprotic solvents must be used, such as acetonitrile... 

P. Winget, E. J. Weber, C. J. Cramer, and D. G. Truhlar, Computational electrochemistry Aqueous one-electron oxidation potentials for substituted anilines, Phys. Chem. Chem. Phys. 2 1231 (2000). 

In the case of anilines, path A will be favoured on the basis of the values of oxidation potentials, in analogy with the gas-phase results. 

Another facet of the reactivity of aminoxyl radicals has been brought to attention by recent studies of the oxidation of substrates endowed with low redox potential. Some aminoxyl radicals, depending on the reduction potential value of the couple >N—O / >N—O, can behave as moderate one-electron abstractor towards substrates endowed with appropriate oxidation potential. This rather unprecedented reactivity feature, outlined in Scheme 10, has been substantiated by the oxidation of aniline or phenol derivatives, whose redox potential is conveniently located in the 0.4-1.0 V/NHE range ". 

With respect to the kinetics of oxidation reactions, the same comments as made in Section 14.2 are, of course, valid. To illustrate, we consider the oxidation of substituted phenols and anilines by Mn02 and of substituted phenols by HC1O4. By analogy to the type of LFER used to evaluate NAC reduction (Eq. 14-38), we can relate oxidation reaction rates to the one-electron standard oxidation potentials of... 

That is, hox(AtXH)= - / (ArX ). For this type of reaction, E (ArX ) is positive. Hence, the more positive this value, the more difficult it is to oxidize the compound. For many phenols and anilines, polarographic half-wave potentials, Zs1/2(ArX"), determined at pH values where the compound is present in its neutral form, are available. These values should reasonably parallel the oxidation potentials of the compounds, and therefore can also be used to relate oxidation rate constants ... 

Nauflett and Farncomb [81] have described the easy destruction of Otto Fuel II, a three-component liquid monopropellant used for torpedo propulsion, by Ce(IV) in a mineral acid electrolyte. Chung and Park [82] have treated aniline solutions with Ce(IV) and Co(III) as mediators, the final product being C02. Parameters affecting current efficiency included oxidation potentials of mediators, their concentrations, and temperature. 

Li et al. [93] have used l-ethylimidazolium trifluoroacetate, which is a Bronsted acidic ionic liquid, as a medium for the electropolymerization of aniline. They report that in this ionic liquid the oxidation potential of aniline is lower (0.58 V compared to 0.83 V in 0.5 M H2SO4) and that the growth rate of the polymer is increased. Further, the resultant films are smooth, strongly adhered to the Pt working electrode and are very electrochemically stable. Similar results have been reported by Liu et al. [92], who found that this was the best ionic liquid for the polymerization of aniline, compared to the unsatisfactory results observed in other protic ionic liquids 1-butylimidazolium tetrafluoroborate, 1-butylimidazolium nitrate and 1-butylimidazolium p-toluenesulfonate, as well as the l-butyl-3-methylimidazolium hydrogen sulfate and l-butyl-3-methyimidazolium dihydrogen phosphate. 

As is shown in Figure 3 the highest occupied energy level is found to parallel well the oxidation potential in aniline and p-phenylenediamine derivatives. To elucidate the existence of the optimum oxidation potentials for antioxidation and antiozonization, the reactivity indices Sr and S for radical and nucleophilic reactions have been used. These are ... 

For the ANI radical cation, an acidity constant pKa = 6.4 was obtained182 however, no experimental BDE of this ion has been reported. A linear correlation of the oxidation potentials of anilines versus the acidities of the corresponding radical cations was observed. Recent ab initio calculations198 derived a value of BDE(N+—H) = 418 10 kl mol-1 for the aniline radical cation, relative to the Ph—N—H+ cation in its singlet ground state. Removal of an electron reinforces the strength of the N—H bond, due to the electron delocalization. 

Dication (35) reacted with aniline and A(,Af-dimethylaniline according to Scheme 4. Aliphatic amines like diisopropylamine did not react. Thiophenol was oxidized by (35) to diphenyl disulfide the difference is probably due to difference in oxidation potentials <90CL393>. 

The yield data for the two compounds can be added to the plot for the results from compounds 36 (Fig. 7) using the oxidation potential for aniline (0.53 V versus Ag ) and 4-methoxyaniline (0.33 V versus Ag" ). The correlation is still very good, providing further support for a mechanism involving homolytic cleavage from S followed by electron transfer in the radical pair to form the ion pair. 

Polythiophenes are another interesting family of conductive polymers that have broad potential applications and technological relevance. However, unlike pyrrole and aniline, the oxidation potential of thiophene is relatively high and is almost insoluble in aqueous media. For this reason, there are only reports dealing with the enzymatic polymerization of (3,4-ethylendioxythiophene) (EDOT), one of the... 

Aromatic amines have such low oxidation potentials that they are ordinarily oxidized when treated with a cation radical. The amine cation radical is then most likely to dimerize. The dimerization reaction may itself be looked upon as either the reaction of the amine cation radical with another molecule of amine or the dimerization of two cation radicals, as is illustrated with N,N-dimethyl-aniline in (145) and (146). The electrochemical literature is replete... 

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