can be offered. The following tautomeric modification of I best represents dehydracetic acid :

The hydrated salts of dehydracetic acid are represented by the formula:

and on heating lose water in the following manner :

Moreover, such a compound might be expected to be coloured, as it possesses three alternate double linkings, which is a colour grouping. Also, should the sodium be replaced by a methyl group, the substance might still possess as much acidity as dehydracetic acid, whilst by the addition of sodium hydroxide and the opening up of the ring, a coloured salt could be formed,

ONa

CH ̧•CO·CH:C(OH)·CH:C(OH)·CH:CO-CH2'

which in presence of water would instantly be hydrolysed. The volatility of the copper salt, the non-existence of xantho-salts, and the action of ammonia on dehydracetic acid also find an easy explanation by means of this formula, although formula II would do equally as well for the purpose.

There is, however, one reaction of dehydracetic acid which can only be explained by formula I, namely, that with phosphorus pentachloride. Two hydroxyl groups are replaced, and a dichloride formed.

CgH8O4 + 2PCI,

=

CHO,C1, + 2HCl + 2POCl3.

A compound represented by formula II could not possibly yield such a derivative. Moreover, Feist (Annalen, 1890, 257, 253) has shown that when this dichloride is heated with sulphuric acid, a true carboxylic acid, isomeric with dehydracetic acid, is produced. He gives it the following formula:

When heated, this acid at once loses carbon dioxide, and dimethylpyrone remains. If formula I represents dehydracetic acid, then the dichloride would be:

and by hydrolysis and loss of hydrogen chloride, an acid,

would remain, which, on heating, should give dimethylpyrone and carbon dioxide, and also possess properties similar to those of acetic acid. Some of the dichloride of dehydracetic acid was therefore prepared, and from it the isomeric acid, CHO. The silver salt of this acid crystallises in plates very similar in appearance to silver acetate; moreover, when boiled with baryta water, acetone and acetic acid are at once produced.

8

The action of ammonia on the acid was investigated. It was heated with excess of ammonia on a water-bath. An acid melting at 258° (corr.) was obtained, which, in properties, resembled in every respect the lutidonecarboxylic acid obtained from ethyl B-aminocrotonate by heating.

Its silver salt was analysed:

Found Ag=39.6. C,H,O,NAg requires Ag= 39.4 per cent.

8 8

for the following reasons. When melted, it decomposes quantitatively into lutidone and carbon dioxide. Its salts are easily decomposed; for instance, a solution of the barium salt, when warmed and shaken

with carbon dioxide, yields barium carbonate and lutidone. The above reactions are not characteristic of an ordinary acid of the pyridine series, but are more in keeping with those of a substituted acetic acid; they also resemble in a marked manner those of an isomeric hydroxylutidinic acid (Trans., 1897, 71, 311), whose constitution is almost certainly represented by the following expression:

A further set of experiments was tried with the object of producing dehydracetic acid from triacetic lactone. If formula II represents the molecular structure of dehydracetic acid, it should not be difficult to reproduce dehydracetic acid from triacetic lactone by means of acetyl chloride.

Triacetic lactone was heated with both acetyl chloride and acetic anhydride. With acetyl chloride, no change occurred, and by prolonged boiling with acetic anhydride only traces of dehydracetic acid were produced. Silver triacetate also, when dried and then added carefully to acetyl chloride, gave only triacetic lactone, after evaporating off the excess of the reagent and extracting the silver chloride with water.

Under certain conditions, however, dehydracetic acid can be made. from triacetic lactone, namely, when it is boiled for some time with sulphuric acid and excess of acetic anhydride. The substance thus obtained possessed all the properties of dehydracetic acid. It melted at 108-109°. After boiling with hydrochloric acid, the concentrated solution gave a precipitate of dimethylpyrone platinichloride. This was analysed:

Found Pt=297. (CHO)2,H,PtCl requires Pt=29.6 per cen

The dimethylpyrone was also converted into the yellow barium salt, and this substance, when dissolved in dilute hydrochloric acid, gave diacetylacetone, which was recognised by the blood-red colour it yielded with ferric chloride.

The conversion of triacetic lactone into dehydracetic acid seems to be very similar to that of benzaldehyde into sodium cinnamate by means of sodium acetate in presence of acetic anhydride:

The sulphuric acid enables the sodium acetate or acetic anhydride to form an additive product with triacetic lactone, and by the elimination of acetic acid, dehydracetic acid is formed:

The connection between acetonedicarboxylic acid and dehydracetic acid (von Pechmann, Ber., 1891, 24, 3600) can be explained in a similar manner. By the action of acetic anhydride, acetonedicarboxylic anhydride is first formed; this reacts with the acetic anhydride to form a dicarboxylic acid, which, when heated, loses carbon dioxide and water, and dehydracetic acid remains:

the last acid, diacetylacetonedicarboxylic acid, being at once converted into the lactone,

which decomposes, when heated, into dehydracetic acid and carbon dioxide.

RESEARCH LABORATORY OF THE PHARMACEUTICAL

SOCIETY OF GREAT BRITAIN.

VOL. LXXVII.

3 x

LXXXVII. Decomposition of Hydroxyamidosulphates by Copper Sulphate.

By EDWARD DIVERS and TAMEMASA HAGA.

WHEN copper sulphate is added to a solution of a hydroxyamidosulphate and the mixture heated, the acid of the salt is quickly decomposed into water, sulphur dioxide, sulphuric acid, amidosulphuric acid, and nitrous oxide, with possibly a little nitrogen. By itself, a heated solution of an alkali hydroxyamidosulphate is in a state of very unstable equilibrium, generally hydrolysing into a solution of hydrogen hydroxylamine sulphate, and always doing so in presence of a trace of acid, whilst in presence of even a trace of alkali it slowly passes into sulphite and hyponitrite (Trans., 1889, 55, 766). In the cold, with alkali and copper salt, the hydroxyamidosulphate becomes oxidised at once to sulphite, sulphate, nitrous oxide, and water, with reduction of the cupric hydroxide (op. cit., 770), and when heated with cupric chloride it reduces the latter to cuprous chloride, becoming itself converted into sulphur dioxide, sulphate, nitrous oxide, and water. Mercuric nitrate oxidises hydroxyamidosulphate more completely, but ferric chloride seems to act like copper sulphate, and liberates sulphur dioxide.

An alkali hydroximidosulphate is also decomposed by copper sulphate, but not so easily, for it can be heated with it at 100° for a short time without change, and only decomposes (but then suddenly) some degrees above that temperature, yielding the products which a hydroxyamidosulphate gives, together with sulphuric acid coming from its hydrolysis into that salt.

Although the presence of much sulphuric acid prevents the action of copper sulphate on a hydroxyamidosulphate, the acid in moderate excess has but little effect.

Sodium hydroximidosulphate, if kept with care, decomposes only very slowly in a way which has hitherto been obscure (Trans., 1894, 65, 541), but if considered in connection with the action of copper sulphate it may be regarded as essentially the same as that brought about by heating it, in solution, with that salt. For, the decomposed hydroximidosulphate contains, besides acid sulphate and hydroxyamidosulphate, both a little gas (nitrous oxide or nitrogen) shut up in its pores which escapes when the mass is dissolved in water, and also a little amidosulphate, which can be separated from the other salts by precipitation with mercuric nitrate (Trans., 1896, 69, 1649, also 1640, 1642).

The decomposition of hydroxyamidosulphates by copper sulphate is