Diphenylamines

The nitrosamines are insoluble in water, and the lower members are liquid at ordinary temperatures. The separation of an oily liquid when an aqueous solution of an amine salt is treated with sodium nitrite is therefore strong evidence that the amine is secondary. Diphenylnitrosoamine is selected as a preparation because it is a crystalline substance and is thus easier to manipulate on a small scale than one of the lower liquid members. For this preparation, a fairly pure (and therefore almost colourless) sample of diphenyl-amine should be used. Technical diphenylamine, which is almost black in colour, should not be employed. 

Required Diphenylamine, i g. ethanol, 8 ml. sodium nitrite, 0-5 g. hydrochloric acid, o-8 ml. 

Prepare two solutions, one containing i g. of diphenylamine in 8 ml. of warm ethanol, and the other containing 0-5 g. of sodium nitrite in i ml. of water, and cool each solution in ice-water until the temperature falls to 5°. Now add o 8 ml. of concentrated hydrochloric acid steadily with stirring to the diphenylamine solution, and then without delay (otherwise diphenylamine hydrochloride may crystallise out) pour the sodium nitrite solution rapidly into the weil-stirred mixture. The temperature rises at once and the diphenylnitrosoamine rapidly crystallises out. Allow the mixture to stand in the ice-water tor 15 minutes, and then filter off the crystals at the pump, drain thoroughly, wash with water to remove sodium chloride, and then drain again. Recrystallise from methylated spirit. Diphenylnitrosoamine is thus obtained as very pale yellow crystals, m.p. 67 68° yield, 0 9-1 o g. 

Tertiary amines containing one alkyl and two aryl groups, such as mono-I ncthyldiphenyhiniir.e, Cl l3(C, l l.diX , arc rarely encountered and arc unimportant. They usually react with nitrous acid with the insertion of a nitroso group into only one of the two available para positions monomethyl-diphenylamine thus gives monomethyl-mono - pnitroso-diphenylamine. Cl hj(C.ill .)N C l 1 jXO, or V-nicthyl-p-nitrosodiphcnylaniine. 

A halogen atom directly attached to a benzene ring is usually unreactive, unless it is activated by the nature and position of certain other substituent groups. It has been show n by Ullmann, however, that halogen atoms normally of low reactivity will condense with aromatic amines in the presence of an alkali carbonate (to absorb the hydrogen halide formed) and a trace of copper powder or oxide to act as a catalyst. This reaction, known as the Ullmant Condensation, is frequently used to prepare substituted diphenylamines it is exemplified... 

B) Secondary amines, (i) Aromatic amines. Monomethyl and monoethylaniline, diphenylamine. (ii) Aliphatic and other amines. Diethyhmine, di-n-propylamine, di-isopropylamine. Also piperidine piperazine diethylene-diamine). 

Physical Properties, (i) Aromatic. Colourless when freshly prepared, but usually brown. MonomethylaniUne, CgHjNHCH, b.p. 193°, and monoethylaniline, CgHjNHCjHj, b.p. 206 , diphenylamine,(C6H5)2NH, m.p. 54 , are all insoluble in water, the two alkylanilines having well-marked basic properties, diphenylamine being feebly basic and insoluble in dilute mineral acids. 

Coloured oxidation products, a) Dissolve a few small crystals of diphenylamine in 1 ml. of cone. H2SO4. Add 2 drops of cone. HNO3 to about 10 ml. of water, shake, and add i drop of this diluted HNO3 to the diphenylamine solution an intense purple-blue coloration is produced. Monomethylaniline merely turns a dirty brown when treated in this way. 

A) Picrates (except diphenylamine). (B) Acetyl Derivatives. (C) Benzoyl, Toluene-p sulphonyl and Benzenesulphonyl Derivatives. (D)... 

Various basic substances, such as aromatic amines (naphthyl-amines dissolve with difficulty in dil. HCl, diphenylamine only in cone. HCl, triphenylamine insoluble) nitro-anilines some amino-carboxylic acids. 

Green coloration. Catechol (colour rapidly darkens). [Aniline (pale green), o-toluidine (pale green initially), mono-methylaniline, and diphenylamine, each in dil. HCl.]... 

Substances suitable for the estimation acetanilide, diphenylamine, glycine, benzanilide. 

Diphenylamine suspension). Bluish-purple changing to a deep permanganate colour. 

The following liquids may be used (boiling points are given in parentheses) — chlorobenzene (132-3°) bromobenzene (155°) p cymene (176°) o-dichloro-benzene (180°) aniline (184°) methyl benzoate (200°) teti-alin (207°) ethyl benzoate (212°) 1 2 4-trichlorobenzene (213°) iaopropyl benzoate (218°) methyl salicylate (223°) n-propyl benzoate (231°) diethyleneglycol (244°) n-butyl benzoate (250°) diphenyl (255°) diphenyl ether (259°) dimethyl phth ate (282°) diethyl phthalate (296°) diphenylamine (302°) benzophenone (305)° benzyl benzoate (316°). 

Pure bromoform is somewhat unstable and darkens on keeping it may be stabilised by the addition of 4 per cent, of its weight of ethyl alcohol or of a small quantity of diphenylamine. 

The nitroso compound (diphenyinitrosamine) of the purely aromatic secondary amine diphenylamine is a crystalline solid, and therefore provides an interesting preparation eminently suitable for students ... 

Dewar and his co-workers, as mentioned above, investigated the reactivities of a number of polycyclic aromatic compounds because such compounds could provide data especially suitable for comparison with theoretical predictions ( 7.2.3). This work was extended to include some compounds related to biphenyl. The results were obtained by successively compounding pairs of results from competitive nitrations to obtain a scale of reactivities relative to that of benzene. Because the compounds studied were very reactive, the concentrations of nitric acid used were relatively small, being o-i8 mol 1 in the comparison of benzene with naphthalene, 5 x io mol 1 when naphthalene and anthanthrene were compared, and 3 x io mol 1 in the experiments with diphenylamine and carbazole. The observed partial rate factors are collected in table 5.3. Use of the competitive method in these experiments makes them of little value as sources of information about the mechanisms of the substitutions which occurred this shortcoming is important because in the experiments fuming nitric acid was used, rather than nitric acid free of nitrous acid, and with the most reactive compounds this leads to a... 

The nitration of very reactive compounds. Under the conditions where less-reactive compounds were nitrated according to a first-order law the nitrations of anthanthrene, diphenylamine, phenol, and resorcinol were... 

In the synthesis of commercial sulfur-heterocycles two interesting reactions are used (i) diphenylamines may be connected by a sulfur bridge in the orfho-positions (ii) the amino grouping of sulfonamides undergoes condensation reactions with neighboring imino- and amide groups. 

The cyclized products 393 can be prepared by the intramolecular coupling of diphenyl ether or diphenylamine(333,334]. The reaction has been applied to the synthesis of an alkaloid 394[335]. The intramolecular coupling of benzoyl-A-methylindole affords 5-methyl-5,10-dihydroindenol[l,2-b]indol-10-one (395) in 60% yield in AcOH[336]. Staurosporine aglycone (396) was prepared by the intramolecular coupling of an indole ring[337]. 

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