Part 8

It was hoped that here, as in the case of the monohydroxy phenols an etherial salt would be obtained. It was found, however, that very little action occurred, save such as was indicated by the development of a bright carmine color in the melted mixture, until a temperature of about 160° was reached. At this point hydrochloric acid was evolved, but the chloride itself undergoes decomposition. Nothing definite could be isolated among the reaction products, save unchanged β-Naphthol.

VIII. The Action of Aniline upon the Symmetrical Chloride of Paranitroorthosulphobenzoic Acid.

As has been pointed out in the Introduction, it was in connection with the aniline derivatives of orthosulphobenzoic acid, that the isomerism of the chlorides was first noticed, two anilids being obtained. Accordingly, when Gray began his study of the chlorides of paranitroorthosulphobenzoic acid, his first effort was to obtain evidence of the existence of two anilids. These were not obtained, however, until after the chlorides themselves had been isolated, as their properties made their isolation and preparation a matter of difficulty.

Some points still remained in doubt after Gray’s study, and a further investigation was thought to be desirable to clear these up.

Some time was spent in an endeavor to obtain a method by which a good yield of fusible, or symmetrical, anilid could be obtained. The yield in all cases tried, is not a good one. The presence of the nitro group appears to complicate the reaction, leading to secondary reactions whose course could not be followed. Upon bringing aniline and the chloride together, a very vivid red color was always observed, and the same was true when it was necessary to employ alkali. The fact that such colors develop when nitro compounds are treated with alkali has been noticed in many instances and some progress has been made in the study of these compounds. Jackson and Ittner have lately reviewed this subject.

If a solution of the symmetrical chloride in ether is slowly added to a similar solution of aniline, no appreciable amount of heat is evolved. If the resulting solution is allowed to stand at ordinary temperatures, action proceeds very slowly, aniline hydrochloride being precipitated as the reaction proceeds. This can be filtered off from time to time and the rate of action so observed. In such a way it was found that five grams of chloride required about fifty hours time to react completely with an excess of aniline. Similar results were obtained with chloroform as the solvent. By boiling the solution for an hour or more the reaction is complete.

Am. Chem. Journ. XIX-199

The method employed was to bring the chloride and an excess of aniline—somewhat more than four molecules—together in chloroform solution. The flask was then boiled for about an hour, when the chloroform was distilled off. During the boiling as well as the distillation more or less bumping occurs in consequence of the aniline hydrochloride which separates, and constant shaking of the flask is sometimes necessary. The residue which is in a thick, gummy condition in consequence of the presence of an excess of aniline, was digested with water acidulated with hydrochloric acid. The excess of aniline is thus removed, and the reaction product obtained as a reddish-brown solid substance. This was treated with dilute sodium hydroxide, all lumps being broken up with a stirring rod. The undissolved substance is largely anil, which was filtered off. The anilid was then regained by acidifying the alkaline solution, in which it was dissolved. It separates immediately as a curdy colorless precipitate, though it is frequently colored pink by impurity. It was found that this color could be removed, in case not much was present, by redissolving the anilid in alkali, and slowly pouring the solution into an excess of dilute acid.

In all cases a considerable amount of anil was obtained, even when the substances were employed in the molecular ratios of 1:10. The reactions involved, so far as the formation of anilid and anil are concerned are,

COCl CO.NH.C₆H₅ / / C₆H₃——SO₂Cl + 4C₆H₅NH₂ = C₆H₃——SO₂.NH.C₆H₅ + C₆H₅NH₃Cl \ \ NO₂ NO₂

CO / \ COCl / N.C₆H₅ / / / C₆H₃——SO₂Cl + 3C₆H₅NH₂ = C₆H₃——SO₂ + 2C₆H₅NH₃Cl \ \ NO₂ NO₂

On the whole the reaction seemed to be the most satisfactory in chloroform solution, the main objection being, that, owing to the simultaneous presence of chloroform, alkali, an a trace of aniline, phenyl isocyanide is always formed, and renders the work more or less unpleasant.

A number of experiments were also made to see if the yield could be increased be employing a modification of the “Schotten-Baumann Reaction” for the formation of anilids. For this purpose an etherial solution of the chloride was added to a like solution of aniline in which was suspended finely powdered anhydrous potassium carbonate. The proportions of the substances were those demanded by the equation

COCl CO.NH.C₆H₅ / / C₆H₃——SO₂Cl + 2C₆H₅NH₂ + 2K₂Cl₃ = C₆H₃——SO₂NH.C₆H₅ + 2KCl + 2KHCO₃ \ \ NO₂ NO₂

Very little anilid was, however obtained, but in its place a substance soluble in water, of acid reaction capable of forming salts and yielding several well characterized derivatives. I hope to investigate this reaction more fully at some future time.

Ber. XVII-2545; XXIII, 3430.

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The anilid is rather sparingly soluble in alcohol, from which it is deposited on cooling in very small needles. These melt, as stated by Gray, at 222°. It is also soluble in chloroform and glacial acetic acid, but does not form well defined crystals from any solvent. It dissolves in dilute alkali from which solution acids precipitate it unchanged.

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The anil is also soluble in alcohol, glacial acetic acid etc. It crystallizes in much better-formed crystals than does the anilid. These melt at 188°.

On boiling the anil with aniline for a time, it is converted into the anilid

CO / \ / N.C₆H₅ CO.NH.C₆H₅ / / / C₆H₃——SO₂ + C₆H₅NH₂ = C₆H₃——SO₂NH.C₆H₅ \ \ NO₂ NO₂

In none of these reactions was any infusible anilid observed.

IX. The Action of Phosphorus Oxychloride upon the Fusible Anilid.

Hunter found that when either of the anilids of orthosulphobenzoic acid were treated with phosphorus oxychloride, or similar dehydrating agents, a molecule of water was abstracted with the formation of a new substance. A careful study of the compound led to the belief that it was a dianil, and that its formation and structure could be represented by the equation

C=N.C₆H₅ / \ CO.NH.C₆H₅ / \ / / .N.C₆H₅ C₆H₄ = C₆H₄ / + H₂O. \ \ / SO₂NH.C₆H₅ SO₂

A corresponding study of the fusible anilid of paranitroorthosulphobenzoic acid was undertaken.

The method employed in this study was as follows. A tubulated retort of convenient size was fused onto the inner tube of a small condenser. This was done to avoid connections, which are nearly always attacked by the oxychloride. Another satisfactory plan is to have the neck of the retort of the same size as the inner tube of the condenser. The ends are placed in contact, and the tubes bound in position by wrapping with asbestos paper. Over the joint so made, a tight rubber tube is drawn.