Aromatic amines anodic processes

Tris(4-bromophenyl)ammoniumyl hexachloro antimonate is commercially available (e.g., Fluka product, 5g cost 70). It is commonly used as an oxidizing reagent by means of electron transfer and is elegantly applied to induce cycloadditions and cyclodimerization ([2 -I- 2] reactions) by Bauld [115]. However, aromatic amine radical cations as the oxidizing reagent can be easily obtained anodically [116] and their redox potentials (between -1-1 V and -1-2 V vs. NHE) modulated as a function of different substituents for utilization if indirect oxidation reactions are to be conducted. Therefore, such a redox catalysis process appears to be a cheap and elegant method to selectively achieved in situ oxidation, provided that polar solvents, electrolytes, and room temperatures are acceptable experimental conditions to perform a given reaction. 

Experiments designed to elucidate the role of S in cathodic reduction tend to be just as ambiguous as their anodic counterparts, unless certain precautions are taken. The possible intervention of S in the reduction of aromatic hydrocarbons (Asahara et al., 1968 Benkeser and Kaiser, 1963 Benkeser et al., 1964 Sternberg et al., 1963, 1966, 1967, 1969) in SSEs made up of amines or HMPA (to which up to 65% ethanol can be added without impairing the stability of HMPA too much) as compared to the possible direct processes taking part in protic solvents illustrates the problem. 

While the process at the cathode always ends finally in withdrawal of oxygen or in taking up of hydrogen, the number of possible reactions at the anode—aside from solution-phenomena, which are without interest here—is a much greater one. For, each ion which is capable of substituting can pass into the reactive state at the anode and produce reactions which cannot be numbered with the real oxidations. In the first place numerous substitutions can occur in difficultly oxidizable bodies, especially aromatic compounds, for instance the chlorination of phenols and phthale ins, nitration of acids, diazotizing of amines, etc. Substitution and oxidation processes often occur simultaneously, as in the electrolytic formation of iodoform from alcohol. 

Simons process — Electrochemical polyfluorination reactions of organic compounds are the only efficient way to industrial production of perfluorinated compounds. The reaction proceeds in the solution of KF in liquid HF (b.p. 19.5 °C), where the starting substances as alcohols, amines, ethers, esters, aliphatic hydrocarbons and halo-hydrocarbons, aromatic and heterocyclic compounds, sulfo- or carboxylic acids are dissolved. During anodic oxidation, splitting of the C-H bonds and saturation of the C=C bonds occur and fluorine atoms are introduced. 

Compounds with reducible functional groups predominate. Polyaromatic hydrocarbons, aromatic hydroxy compounds and amines, as well as amides and various nitrogen heterocyclic compounds can be determined anodically. These processes are in many cases pH dependent. Determinations based on redox processes are therefore carried out in buffered solutions. The composition and concentration of the buffer systems generally has no influence on the position of the half-wave or peak potentials. If its concentration is sufficiently high, the buffer simultaneously performs the function of the supporting electrolyte. 

---