Diphenylbenzidine

Mention should be made of one of the earliest internal indicators. This is a 1 per cent solution of diphenylamine in concentrated sulphuric acid, and was introduced for the titration of iron(II) with potassium dichromate solution. An intense blue-violet coloration is produced at the end point. The addition of phosphoric(V) acid is desirable, for it lowers the formal potential of the Fe(III)-Fe(II) system so that the equivalence point potential coincides more nearly with that of the indicator. The action of diphenylamine (I) as an indicator depends upon its oxidation first into colourless diphenylbenzidine (II), which is the real indicator and is reversibly further oxidised to diphenylbenzidine violet (III). Diphenylbenzidine violet undergoes further oxidation if it is allowed to stand with excess of dichromate solution this further oxidation is irreversible, and red or yellow products of unknown composition are produced. 

Diphenylamine-4-sulphonic acid, sodium salt 375, 377, 381 Diphenylbenzidine 366... 

A second important group includes the diphenylamine indicators. In the presence of a strong oxidizing agent, diphenylamine is irreversibly converted to diphenylbenzidine. This latter compound undergoes a reversible redox reaction accompanied by a colour change,... 

N,N -Diphenylbenzidine [53I-9I-9J M 336.4, m 245-247 . Crystd from toluene or ethyl acetate. Stored in the dark. 

Reduction of diphenylbenzidine with arsenic(III) oxide shows a first-order dependence on hydrogen ions, As(III), and the substrate. The activation parameters have been determined.390... 

Sulfonic acid derivatives of diphenylamine and diphenylbenzidine are suitable indicators in many redox titrations. The structures of these indicators are shown below ... 

The redox reaction between diphenylbenzidine and thiosulfate is of first order with respect to thiosulfate, diphenylbenzidine, and hydrogen ions.301 Zinc-diamine-catalysed reduction of various ketones with polymethylhydrosiloxane in protic conditions show moderate enantioselectivities. Probable mechanisms are proposed.302 Reduction of non-activated aryl and alkyl halides by a neutral ground-state organic molecule (13) afforded the corresponding indolines in excellent yields. A tentative mechanism has been suggested (Scheme 13).303... 

Sinicropi et al. (1996) measured hole mobilities of N,N -bis(2,2-diphenyl-vinyl)-N,N -diphenylbenzidine (ENA-B) doped PS. ENA-B is a weakly polar molecule with a dipole moment of 0.86 Debye. In agreement with earlier work of Sugimura et al. and Han et al., the mobilities were unexpectedly high, exceeding 10-3 cm2/Vs at high concentrations and high fields. Figure 61 shows the field dependencies of the room temperature mobilities for different... 

Table 8 Hole Transport Properties of N,N -bis(2,2-diphenylvinyl)-N,N/-diphenylbenzidine (ENA-B) Doped into a Series of Polymers. The ENA-B Concentration was 45% (After Siniaropi et al. 1996a)...

The interest in the application of indicators in oxidation-reduction titrations has followed on the discovery that the familiar color change undergone by diphenylamine on oxidation could be used to determine the end-point of the titration of ferrous ion by dichromate in acid solution. Diphenylamine, preferably in the form of its soluble sulfonic acid, at first undergoes irreversible oxidation to diphenylbenzidine, and it is this substance, with its oxidation product diphenylamine violet, that constitutes the real indicator. ... 

Copper(II) and cerium(IV) have been studied as oxidants in acetonitrile. The copper(II)-copper(I) couple has an estimated electrode potential of 0.68 V relative to the silver reference electrode. It has been studied as an oxidant for substances such as iodide, hydroquinone, thiourea, potassium ethyl xanthate, diphenylbenzidine, and ferrocene. Cerium(IV) reactions are catalyzed by acetate ion. Copper(I) is a suitable reductant for chromium(VI), vanadium(V), cerium(IV), and manganese(VII) in the presence of iron(III). For details on many studies of redox reactions in nonaqueous solvents, the reader is referred to the summary by Kratochvil. ... 

VI. Treatment with Diphenylbenzidine Reagent. Place a few small crystsof unknown in an indenture of a white porcelain spot test, add 2 drops of diphenyl-benzidine reagent(a satd soln of C Hg.NH.CgH. C5H. NH.CgHj in glac AcOH), and then 1 drop of coned H SO. Observe the color after 1 min. A blue color indicates one of the following expls TNT, TNAns or HNDPhA yel color or no color -PA, AmmPic or DNPh (See also Chart B)... 

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