SCHWALBE A N D WOLFF : STUDIES IN THE CARBAZOLE SERIES. 103

XII.-Studies in the Carbaxole Series. By CARL GUSTAV SCHWALBE and SALOMON WOLFF.

THE object of this research was to prepare mercaptans of carbazole with the intention of converting them into sulphide dyes. Por this purpose we have investigated several possible methods of pre- paration, but in most cases have found that5 instead of obtaining the required mercaptan, the derivatives employed were reconverted into carbazole itself.

I n the first place, we endeavoured t o prepare carbazole mercaptan from 3-aminocarbuole by means of the diazo-reaction. This com- pound was diazotised and treated with copper powder and sulphurous acid, and later also with copper thiocyanate paste. We were not successful in isolating a mercaptan from the products of reduction, but obtained instead carbazole itself. We also proved that the latter is formed on boilin2 a solution of diazotised 3-aminocarbazole,

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104 SCHWALBE AND WOLFF:

or by treating such a solution with cuprous chloride, according to Sandmeyer.

Another possible method of preparing such mercaptans, namely, by the reduction of the sulphonyl chlorides, cannot, in the case of carbazole, be applied, since the monosulphonic acids are at present unknown. We have, however, closely examined the reduction products of the di- and tri-sulphonic acids of carbazole, prepared according to Schultz and Hauenstein's method (J. pr. Clzem., 1907, [ji], 76, 336), but we have only obtained very small quantities of an impure substance with mercaptan-like properties, although we have varied the experimental conditions in many ways.

It was not improbable that monosulphonic acids of carbazole, on reduction, would behave differently from the disulphonic acids, and we accordingly carried out a great number of different sulphonating experiments, always obtaining, however, disulphonic acids, of which we identified two new isornerides.

Furthermore, if both nuclei in carbazole are symmetrically sulphonated, it might be possible that, on introducing, for example, a nitro-group into one nucleus, the other nucleus would take up a single sulphonic acid group, and only a monosulphonic acid would be obtained. On reduction, diazotisation, and boiling with alcohol, such a nitrocarbazolemonosulphonic acid might be expected to yield a carbazolemonosulphonic acid.

We accordingly sulphonated 3-nitrocarbazole, but did not obtain a monosulphonic acid, so that this method also could not be used.

Carbazole may be synthetically prepaxed from phenylbenzo- triazoles according t o Graebe and Ullmann (AnmaZen, 1896, 291, 16), and we have attempted to apply a modification of this synthesis to the preparation of a, monosulphonic acid by making use of o-nitrodiphenylaminep-sulphonic acid. This should be convertible into the corresponding azimino-compound, and the latter into a carbazolemonosulphonic acid. We succeeded, in fact, in preparing 1-phenyl-1 : 2 : 3-benzotriazole-5-sulphonic acid, but, on heating it,, obtained carbazole itself instead of the expected monosulphonic acid. It would therefore seem that at the high temperature of formation the monosulphonic acid of carbazole decomposes, with formation of carbazole. I n further support of this, we have shown that on heating the salts of the disulphonic acids of carbazole a t a high temperature, carbazole is regenerated. Schultz and Hauenstein have also proved that the potassium salt of a disulphonic acid of carbazole, on being heated with potassium cyanide, gave rise to carbazole. From these data it seems clear that certain of the carbazole derivatives show in their reactions a strong tendency to regenerate carbazole, and t4hat the ordinary transformations

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STUDIES IN THE CARBAZOLE SERIES. 105

which occur readily in the benzene series do not here take place.

EXPERIMENTAL.

3-A mino car6 acole.

Ruff and Stein (Ber., 1901, 34, 1677) obtained 3-aminocarbazole on reducing nitronitrosocarbazole with stannous chloride and hydre chloric acid. We modified this method by using technical sodium sulphide. Nitronitrosocarbazole is mixed with 10 parts of 96 per cent. alcohol, and to this mixture 10 parts of concentrated sodium sulphide solution are added. A deep red coloration is produced, and t'he mixture has an ammoniacal odour. The product is heated on the water-bath until a sample of the mixture no longer gives a red colour with aqueous sodium sulphide. As intermediate product, a substance, melting at 210°, was isolated, which was probably identical with nitrocarbazole. The methods described in D.R.-P. 122852 and 134983, and also that recommended by Ziersch (Ber., 1909,42 , 3797), namely, reduction with sodium hyposulphite, led, in our experiments, to less pure products.

Carbazoledisulphonic A cids.

Schultz and Hauenstein heated carbazole with the quantity of concentrated sulphuric acid necessary for the formation of a mono- sulphonic acid, at a temperature of from 70° to 75O during six to seven hours. After conversion into the barium salt, these authors obtained a separation of crystals only after the concentrated solution had been kept for a long time, but the barium salt prepared by us crystallised out direct-ly on cooling the solution, as a voluminous, colourless mass. On reconverting this barium salt into the potassium salt, and treating the latter with phosphorus penta- chloride, a diszclphonyl chloride was obtained, which crystallised from acetone in colourless leaflets, and gave, with ammonia, unlike Schultz and Hauenstein's product, a disulphonamide, having no definite melting point.

When heated under pressure with 48 per cent. sulphuric acid a t 120°, or with water a t 130°, the potassium salt of this acid gives rise to carbazole.

The disulphonyl chloride gave on analysis: 0.1488 gave 0.123 AgCl. C1=20*45. 0.1668 ,, 0.2058 BaSO,. S=16.92.

C,,H70,NC1,S, requires C1= 19.50 ; 8 = 17.58 per cent,

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106 SCHWALBE AND WOLFF : STUDIES IN THE CARBAZOLE SERIES.

Analysis of t3he disuZphonumide furnished the following numbers : 0.175'gave 0.2518 BaSO,. S = 19.76. 0.148

C12H1104N3S2 requires S = 19.69 ; N = 12.92 per cent. Carbazole is readily sulphonsted on treatment with mono-

potassium disulphate, KH3(S0,),, at about looo. The potassium salt of the sulphonic acid formed proved t o be a mixture of di- and tri-sulphonic acids.

We have also found that carbazole is easily sulphonated by 67 per cent. sulphuric acid.

Ten grams of carbazole are heated with 50 C.C. of 67 per cent. sulphuric acid at 115O for some hours, t.he mixture being stirred. By this process a fairly soluble barium salt and a crystalline potassium salt of carbazolediszclpT~onic a(cid are produced. The disulphonyl chloride melts at 102O, reacts in the cold with ammonia, giving a yellow coloration, and finally dissolves, but a disulphonamide could not be obtained.

On heating the potassium salt with 48 per cent. sulphuric acid or with water under pressure, it remains unaltered, and in this respect also differs from the above-described disulphonic acid, which regenerates carbazole.

,, 16.5 C.C. N, a t 21O and 750 mm. N=12.97.

On analysis of the potassium salt: 0.1500 gave 0.1628 BaSO,. S = 15.20. 0.1500 ,, 0.1630 BaSO,. S=15*21.

C',,H70,NS,K2 requires S = 15.88 per cent. The disdphonyl chloride was also analysed : 0.1520 gave 0.1218 AgCl. C1= 19-83. 0.1520 ,, 0.1214 AgC1. C1=19*76.

C,,H70,NC12,S, requires C1= 19-50 per cent. Thus the existence of a t least two isomeric disulphonic acids is

shown by these experiments. The difference in properties exhibited by the acid prepared by us by Schultz and Hauenstein's method cannot as yet be satisfactorily explained.

Sulphonation of 3-Nitrocarbazole.

Five grams of 3-nitrocarbazolel were heated with 25 C.C. of 67 per cent. sulphuric acid at 130-140° until dissolved. After separation of a tarry by-product, the filtrate was treated with barium carbonate, and a yellow, amorphous barium salt was isolated, which could not be obtained crystalline :

0.428 gave 0.3832 BaSO,. 0.1554 ,, 0.1270 BaSO,. S=11.22.

Ba = 24.30.

Cl2H,O8N,S2Ba requires Ba = 26.95 ; S = 12.62 per cent.

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PURVIS : ABSORPTION SPECTRA, ETC. 107

These results indicate that a mixture of mono- and di-sulphonic acid is formed.

On reducing the nitrocarbazolesulphonic acid by Claisen’s method, a small quantity of a silver-grey potassium 3-arninocarbazoledi- s ulphonat e was isolated :

0.1436 gave 8.2 C.C. N, at 2 2 O and 747 mm. N = 6.4. CT,2H,N,0,S,K, requires N = 6.7 per cent.

I-PhenyZ-1 : 2 : 3-benzotriazole-5-suZphonic A cid.

This acid was obtained by the diazotisation of o-aminodiphenyl- amine-p-sulphonic acid. The latter was prepared by the action of aniline on p-chloro-m-nitrobenzenesulphonic acid, and reduction of the o-nitrodiphenylaminesulphonic acid formed.

o-Aminodiphenylaminesulphonic acid is described in the literature as an indistinctly crystalline solid. We obtained it in well-defined slightly violet needles.

On diazotisation, a red solution was obtained, which did not combine with phenols. On evaporation of this, a brown, amorphous substance separated out, which, on being slightly heated on platinum foil, swells up and leaves a grey, iridescent mass. On slowly heating this triazole a t 390-400°, carbazole sublimes on the sides of the vessel :

0.1504 gave 17.8 C.C. N, at 15O and 757 mm. 0.1504 ,) 18.4 C.C. N, ,, 15O ), 757 mm. N=14*13. 0-1488 ,, 0.1090 BaSO,. S = 10.6.

N=13.8.

C,,H,O,N,S requires N = 15.27 ; S = 11.63 per cent. INSTITUTE FOR ORGANIC UHEMISTRY,

TECHNISCHE HOCHOCHULE, DARYSTADT.

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