642

MIXED ETHERS OF ALLYL.

position analogous to that which attends the formation of ordinary ether when sodium-alcohol is treated with ethyl iodide (p. 204).

Berthelot and De Luca state that allyl oxide may also be formed by distilling allyl iodide with mercuric oxide. It is lighter than water, and has an ethereal odour resembling that of radishes.

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Allyl oxide appears to exist ready formed in small quantity in oil of garlic, and in some other oils which resemble it. Wertheim also states that it may be obtained by decomposing oil of mustard by distillation in a closed tube with caustic soda and lime, but the decomposition of the allyl sulphocyanide thus effected is slow and imperfect. It enters into direct combination with nitrate of silver, and forms a compound [(E,H.),0, 2 AgNO3], which may be obtained by mixing rectified essence of garlic with an excess of a concentrated alcoholic solution of nitrate of silver: in the course of twenty-four hours a black deposit of sulphide of silver is formed; the liquid must be boiled, and filtered; on cooling, the compound of allyl oxide with nitrate of silver crystallizes in brilliant colourless radiated prisms, which are freely. soluble in water, but sparingly so in cold alcohol. If this body be dissolved in ammonia, allyl oxide is set at liberty.

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A double allylic ether has also been formed by decomposing allyl iodide by an alcoholic solution of potash; in which case allyl-ethylic ether (¤ ̧н¿‚¤‚Í ̧‚Ð), a liquid which boils at 144°5 (62.5 C.), is produced. Allyl-amylic ether [Є,H,,,H,,; Boiling pt. 248° (120° C.)], may be obtained by substituting a solution of potash in fousel oil for the alcoholic solution of potash used in the previous experiment.

Hofmann and Cahours have obtained the same compounds by decomposing potassium-allyl-alcohol by ethyl iodide, and by amyl iodide.

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(1472) Allyl Chloride (Є,H,Cl) is readily obtained by distilling allylic alcohol with phosphoric chloride, and the bromide (ЄH.Br) may be obtained with equal facility by distilling the alcohol with phosphoric bromide.

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Allyl Iodide; Iodized Propylene (Є,H,I=168); Sp. gr. of liquid 1789; Boiling pt. 214° (101° C.).—This interesting compound is obtained by the action of equal parts of phosphorus diniodide and glycerin upon each other (1238). It is a colourless liquid, insoluble in water, but soluble in alcohol and in ether; it

BROMINE COMPOUNDS OF ALLYL-ALLYL SULPHIDE.

643

has an ethereal, somewhat alliaceous odour; when exposed to air and light it rapidly becomes brown, and emits an irritating odour allied to that of mustard; it may be distilled unaltered. Allyl iodide is decomposed by digestion with an aqueous solution of ammonia, and on distillation with potash a volatile base of a fishy ammoniacal odour is formed, probably allylia (¤ ̧H,N=¤‚H¿‚H2N).

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The following compounds investigated by Wurtz (Ann. de Chimie, III. li. 87) are connected with these bodies:

(1473) Tritylene Dibromide (Є,H,Br2); Boiling pt. between 284° (140° C.) and 293°.—This is a colourless liquid, having the odour of Dutch liquid. It is most readily prepared by transmitting through bromine the gaseous products procured by passing the vapours of fousel oil through a red-hot tube, and submitting the liquid thus obtained to fractionated distillation. This substance may be regarded as the hydrobromic ether of tritylic glycol.

Bromotritylene Dibromide (Є,H,Br,Br,); Sp. gr. of liquid 2392; Boiling pt. about 383° (195° C.).-When the vapour of the foregoing compound is submitted at its boiling point to the action of the vapour of bromine, the two bodies react upon each other, hydrobromic acid gas is formed, and a new brominated substance having the above formula is obtained. After purification by distillation it is procured in the form of a colourless liquid of a powerfully irritating and very persistent odour. acts rapidly upon the salts of silver.

It

A compound, metameric with the foregoing one, which has been termed allyl tribromide (ЄH.Br ̧), is obtained by decomposing 1 part of allyl iodide with 24 parts of bromine. It has a sp. gr. of 2'436, and boils at 423° (217 C.), but unlike its isomeride it becomes converted into a solid mass at temperatures below 50°. When cooled slowly it deposits magnificent brilliant prisms fusible at 62° (17° C.). An alcoholic solution of potash decomposes it, liberating an ethereal compound which boils at 275° (135° C.).

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Allyl tribromide is readily attacked by acetate of silver, I atom of the bromide requiring 3 atoms of the acetate for its decomposition. It is thus converted into triacetin (E,H1106); and this substance, when decomposed by baryta water, yields a product which, when purified by distillation in vacuo at 392° (200° C.), was found to be pure glycerin.

(1474) Allyl Sulphide (H.); Boiling pt. 284° (140° C.). -This compound is contained in various essential oils, particularly in those of garlic, of onions, of leeks, of cress, of radishes, and of assafoetida. It may be prepared artificially by allowing allyl iodide to fall drop by drop into an alcoholic solution of

dipotassic sulphide. A slight excess of the alkaline sulphide must be maintained, and, on diluting the mixture with water, the allyl sulphide is separated in the form of a yellowish limpid oil. When rectified, allyl sulphide is a colourless oil which is lighter than water; it has a high refracting power; its odour is less repulsive than that of crude oil of garlic. It may be distilled without undergoing decomposition; concentrated nitric acid converts it into formic and oxalic acids, whilst the sulphur is oxidized. Cold sulphuric acid dissolves it with a purple tint, but the oil is separated unaltered on dilution. It is dissolved rapidly by hydrochloric acid, and the mixture acquires a deep blue colour, which disappears on the addition of water. Solutions of the alkalies do not decompose allyl sulphide.

Allyl sulphide causes a precipitate in many metallic solutions, such as those of silver, mercury, gold, platinum, and palladium, but it does not precipitate the salts of lead or of copper. The nitrate of silver gradually decomposes it, sulphide of silver being formed, and the compound of allyl oxide and nitrate of silver (1471) is produced. A peculiar sulphuretted compound of allyl with mercuric chloride is obtained by mixing alcoholic solutions of allyl sulphide and corrosive sublimate, when an abundant white precipitate is formed [(ЄH ̧) ̧§‚ 2 Hg§‚ 2 ¤ ̧H ̧Cl, 2 ĦgCl,]. If this compound be distilled with potassic sulphocyanide it is decomposed, and oil of mustard mixed with allyl sulphide is amongst the products:

Sulphocy. potass.

[(Є,H.),S, 2HgS.2€,H ̧Cl, 2 HgCl2] +6 K€NS = 6KCl + 2 HgS

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Mercuric sulphocy. Essence of garlic. Essence of mustard.

+ 2 [Hg(ENS),] + (Є3H5)2S + 2(¤ ̧H¡,ENS);

in this reaction the double chloride of mercury and allyl is alone acted upon by the sulphocyanide, potassic chloride and mercuric sulphocyanide being formed, whilst the allyl sulphide passes over unaltered, accompanied by the oil of mustard, leaving mercuric sulphide in the retort.

Essence of Garlic.—When the cloves of garlic are distilled with water, a brown heavy fœtid oil passes over, constituting little more than o'2 per cent. of the fresh root. It is partially decomposed by redistillation over an open fire, but if rectified from a bath of salt water, about two-thirds of the oil may be obtained in the form of a yellowish liquid which is lighter than water, and which, when treated with calcic chloride, and subsequently distilled from fragments of potassium, furnishes pure allyl sulphide.

ALLYL SULPHOCYANIDE-ESSENCE OF MUSTARD.

645

The crude oil appears to contain portions of allyl oxide, and of a higher sulphuretted compound of allyl, which becomes decomposed during the distillation.

The essence of assafœtida contains a larger proportion of sulphur than that of garlic; it evolves sulphuretted hydrogen spontaneously, and cannot be redistilled without undergoing decomposition.

(1475) Allyl Sulphocyanide (Є,H,,ЄNS); Sp. gr. of liquid 1010; of vapour 3'54; Boiling pt. 298° (148° C.).—This compound constitutes the principal portion of the essential oil of mustard, from which it may be obtained in a state of purity by simple redistillation; this operation frees the essence from a brown resinous matter with which it is usually contaminated. The pungency of the horseradish, of the scurvy-grass, and of one or two other allied plants is also due to allyl sulpbocyanide. Berthelot and De Luca made the interesting observation that when allyl iodide is distilled with potassic sulphocyanide, an oil is formed identical with the chief constituent of essence of mustard-an observation which afforded the first indication of the intimate relation subsisting between the allylic series and that of glycerin :

The seeds both of the black and of the white mustard (Sinapis nigra and alba) yield by expression a large quantity of a bland fixed oil, but they do not contain any essential oil ready formed; white mustard does not yield allyl sulphocyanide.*

According to Babo and Hirschbrunn, white mustard contains the hydrosulphocyanate of a peculiar alkali, termed sinapine, EH23 NO. This base, when acted upon by caustic potash or soda, is decomposed into a salt of sinapic acid, and a new alkali, termed sinkaline, in the manner represented in the following equation, adopting the altered formula €16H23NO, proposed by Gerhardt:

An aqueous solution of sinapine has an intensely yellow colour. Sinapine cannot be isolated in a pure condition, owing to the facility with which it is decomposed: it forms crystallizable salts. The hydro-sulphocyanate is extracted from white mustard, after treating the dried flour successively with ether and absolute alcohol to remove the fixed oil and colouring matter, and then boiling the residue in alcohol of sp. gr. 0825. After the solution has been sufficiently concentrated by evaporation, the salt is deposited in crystals as the liquid cools. If the solution of this salt be mixed with an alkali, it assumes an intensely yellow colour, and on boiling the solution, and subsequently adding hydrochloric acid in slight excess, sinapic acid is deposited. If baryta water be used to decompose the salt of sinapine, the sinapic acid is precipitated as an insoluble baric sinapate, and sinkaline

646

ALLYL SULPHOCYANIDE-SINAPIC ACID.

The black mustard, however, contains the potassium salt of a compound termed myronic acid, which is susceptible of a decomposition analogous to that experienced by amygdalin. This decomposition is not effected until the crushed seed is moistened with water; a peculiar azotised ferment contained in the seed, and analogous to the synaptase of the almond, is thus brought into action, and the essential oil is developed.

Ludwig and Lange (Knop's Centralblatt, 1861, p. 149) obtained 1 part of potassic myronate from 500 of black mustard, crystallized in colourless brilliant needles; and according to their analysis this salt consists of KЄ20H3N2S4019: it splits into oil of mustard, sugar, and probably also into hydropotassic sulphite, as follows:

:

The essence of mustard is a colourless oil of a burning and painfully penetrating odour, which produces a copious flow of tears. If the essence be applied to the surface of the body, it speedily raises a blister upon the part. Essence of mustard is soluble in all proportions in alcohol, and in ether, but very sparingly so in water if exposed to the air it absorbs oxygen and becomes brown. When hot it dissolves both sulphur and phosphorus in considerable quantities, but, as the solutions cool, these bodies are again deposited in crystals. Oil of mustard can be converted into essence of garlic by heating it to a temperature of 250° for some hours in a sealed tube, with dipotassic sulphide :Essence of garlic. Potassic sulphocy.

Essence of mustard.

2 (¤ ̧H ̧‚¤NS) + K2S = (¤ ̧H ̧),S + 2 (K,ENS).

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(1476) Oil of mustard combines at once with ammonia, and forms a compound which enters into direct combination with acids like a true organic base; from its origin this compound has been termed thiosinnamine: ·

may be obtained from the solution. Sinapic acid crystallizes in prisms; it is sparingly soluble in cold water, very soluble in boiling alcohol, and insoluble in ether; it fuses at a temperature above 302° (150° C.): nitric acid dissolves it, and produces an intense red colour.

Sinkaline may be obtained in deliquescent crystals, which absorb carbonic acid from the air; it is a powerful base, but readily undergoes decomposition. With platinic chloride it forms a magnificent double salt, which crystallizes in orange-coloured six-sided prisms [2 (е,H,,NO,HCl),PtC1⁄4, 2 H„0].

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