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,
COClCO.NH.C₆H₅
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C₆H₃—SO₂Cl + 4C₆H₅NH₂ = C₆H₃—SO₂.NH.C₆H₅ + C₆H₅NH₃Cl
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NO₂NO₂
CO
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COCl/NH.C₆H₅
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C₆H₃—SO₂Cl + 3C₆H₅NH₂ = C₆H₃—SO₂ + 2C₆H₅NH₃Cl
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NO₂NO₂
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”[25] 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
COClCO.NH.C₆H₅
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C₆H₃—SO₂Cl + 2C₆H₅NH₂ + 2K₂Cl₃ = C₆H₃—SO₂NH.C₆H₅ + 2KCl + 2KHCO₃
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NO₂NO₂
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.
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.