–ˆ• The allyl iodide can then, similarly to the alkyl iodides, be converted into the salts of allyl, and these again by saponification into allyl alcohol.

By slowly heating a mixture of 4 parts glycerine with 1 of crystallised oxalic acid, with addition of a little ammonic chloride, to between 220° and 230°, and then to about 260°, a mixture first passes over of aqueous formic acid and allyl alcohol, and above 195° glycerine monoformate principally distils, which by repeated distillation splits up into water, carbonic oxide, and allyl alcohol:

C3H5(OH)2O.CHO = CO2 + OH2+ C3H5.OH.

2

After saturating the collected distillates with K,CO, the allyl alcohol separates on the surface, and is further purified by distillation first over solid KHO and finally over BaO.

The general behaviour of the allyl compounds is quite analogous to that of the alkyl derivatives. The most important difference consists in that the allyl compounds, as primary substitution products of propylene, enter into direct combination with the halogens and hypochlorous acid, &c., to form glycerine compounds:

664. Halogen Compounds of Allyl.-Allyl chloride :

CH2:CH.CH,Cl,

isomeric with monochlor propylene (§ 658), is prepared by the action of PC13 or HCl on allyl alcohol:

CH2:CH.CH2.OH + HCl = CH2:CH.CH2.Cl + OH2,

and also from allyl iodide by the action of HgCl,:

2C2HI+HgCl2 = 2C2H¿Cl + HgI2.

It is a colourless liquid, of disagreeable smell, boiling at 46°, insoluble in water, and having at 0° the sp. gr. 954.

Allyl bromide, C3H,Br, resembles the chloride; it boils between 70°-71°; sp. gr. 1.461 at 0°. It combines with HBr to trimethene dibromide (479).

Allyl iodide, CH2:CH.CH2I, is an oily liquid of sp. gr. 1·789 at 16°, smells strongly like leeks, and boils at 101°. It is converted by zinc and HCl into propylene (§ 658), by heating with HI into propylene and isopropyl iodide :

CH2:CH.CH2I + HI = I2+ CH2:CH.CH3

2

CH2:CH.CH2I + 2HI= I2+ CH2.CHI.CH3.

2

On agitating an alcoholic solution of C3H,I with metallic mercury, colourless, leafy crystals, quickly turning yellow in sunlight, of mercury allyl iodide (comp. § 361) crystallise out:

CH2:CH.CH2I + Hg = CH2:CH.CH2.HgI,

which, treated with HI, yield propylene gas:

CH2:CH.CH2.HgI + HI = CH2:CH.CH3 + Hg12.

665. Allyl alcohol, CH2:CH.CH2.OH, obtained as above described, is a colourless and mobile liquid of a sharp smell and sp. gr. at 0° of 858. It boils between 96° and 97°, and crystallises to a colourless mass at a temperature of -50°. It combines directly with the halogens to glycerine monohydro-dihaloids, e.g.

CH2CI.CHCI.CH2.OH.

By oxidising agents it is converted first into acroleïn and then into formic acid.

Nascent hydrogen does not combine with it at the ordinary temperature, but by heating with potash to 100°-105° formic acid, ethyl alcohol, primary propyl alcohol, and some products containing less hydrogen, which have not been much investigated, are produced. Potassium and sodium dissolve in allyl alcohol with disengagement of hydrogen and formation of bodies analogous to the alkylates of the alkalies:

2CH2:CH.CH2.OH + Na2 = H2+ 2CH2:CH.CH2.ONa.

2

666. Ether-like compounds of allyl are obtained by the reaction between metallic allylates and the halogen compounds of the alcohol radical.

Allyl ether, or diallyl oxide, (CH2:CH.CH2)2O, is formed according to the following equation:

C3H5>O,
C3H5

and also by the action of allyl iodide on the oxides of mercury or silver:

2C,H,I+Ag20 = (C3H5)2O + 2AgI.

It is a colourless liquid, insoluble in water, boiling at 82°. A small quantity appears to occur naturally in oil of garlic.

Allyl-methyl ether, CH2:CH.CH2.O.CH, from sodic methylate and allyl iodide, is a colourless liquid boiling at 46°.

Allyl-ethyl ether, CH2:CH.CH2.O.CH2.CH3, obtained in a similar manner, boils at 64°.

667. The allyl salts are most easily obtained by the reaction between allyl iodide and the silver salts of the acids.

Allyl acetate, CH2:CH.CH2.O.CO.CH3, boils between 98° and 100°. The formate is found in small quantities, along with formic acid and allyl alcohol, among the products resulting from heating glycerine with oxalic acid. It is lighter than water and boils between 82° and 83°. Both salts have a very sharp smell.

Allyl butyrate boils at 140°, isovalerate about 162°.

4

Monallyl sulphate, C3H5.HSO4, is formed by mixing H2SO, and allyl alcohol; its barium salt is soluble in water.

10°.

Allyl nitrate, CH2: CH.CH2.O.NO2, boils at 106°, sp. gr. 1.09 at

668. Allyl Sulphur Compounds.-Thio-allyl alcohol, or allyl mer

captan, CH2:CH.CH.SH, is formed by the action of C3H,I on an alcoholic solution of potassic sulph-hydrate :

C2H,I + KSH = KI + C2H.SH.

It is very similar to the ethyl mercaptan, and boils at 90°. The sulphur is easily replaced by metals, especially mercury.

It gives by oxidation with nitric acid allyl sulphonic acid, CH2:CH.CH2.SO2.OH, the barium salt of which crystallises in shining prisms.

Diallyl sulphide, or thio-allyl ether:

CH2:CH.CH2.S.CH2.CH:CH2,

is the principal constituent of the yellow ethereal oil obtained by distilling garlic (Allium sativum) with water, from which it is obtained by repeated fractionation and rectification over potassium. It also occurs in the leaves and seeds of many Cruciferæ (Alliaria officinalis, &c.), and is obtained synthetically by the reaction between C3H,I and K,S in alcoholic solution.

In the pure form it is a colourless oil, of a powerful garlic-like odour, boiling at 140°.

669. Nitrogen Compounds of Allyl.-Allyl yields with nitrogen compounds similar to those of the alcohol radicals.

Allyl iodide and ammonia react, forming the iodides of the various allylamines, from which a mixture of the free bases is liberated by treatment with potassic hydrate. The separation of the individual constituents in a state of purity is attended with the usual difficulties. Allylamine, CH2:CH.CH2.NH2, is most easily obtained in the pure form by reducing allyl mustard oil with zinc and HCl in alcoholic solution :

CH2:CH.CH2.N:CS + 2Zn + 5HCl = CH2:CH.CH2.NH2HCI + 2ZnCl2 + CH2S.

On distilling the product of the reaction with OKH, it is obtained as an ammoniacal liquid of sp. gr. 864 and boiling point 58°.

The principal product of the reaction between allyl iodide and ammonia :

4C,H,I + 4NH2 = 3NH1I + N(C3H5),I, tetrallyl ammonium iodide, is precipitated from its aqueous solution by KHO as a syrup, and crystallises in vacuo over H2SO4 after some time. By treating its solution with argentic hydrate tetrallyl ammonium hydrate, N(C3H5),OH, a caustic alkaline liquid, is obtained, which on heating decomposes principally into triallylamine, N(C3H5), a basic volatile oil.

670. Allyl pseudo-cyanate, or allyl carboxylamine :

is formed by heating allyl iodide and potassic pseudo-cyanate together. It is a sharp-smelling oil, which boils at 82° and excites to tears. By gently heating with water it splits up into CO2 and diallyl urea, or sinapoline (comp. § 280):

2C3H5.N:CO + OH2 = CO2 + (C2H2)HN.CO.NH(C2H2), which crystallises in large leafy crystals, melting at 100°.

It combines directly with ammonia to form monallyl urea :
C3H5.N:CO + NH2 = (C3H5).HN.CO.NH2,

and with ethylamine to form ethyl-allyl urea:

(C,H,).HN.CO.NH(C,H),

which crystallises in fine prisms.

671. Allyl mustard oil, or allyl pseudo-sulpho-cyanate:

CH2:CH.CH2.N:C:S

(comp. §§ 284 and 285). Black mustard seeds contain the potassium salt of a glucoside acid, myronic acid, which, in presence of water and a ferment existing in the seeds (myrosine), is converted into sugar, hydric potassic sulphate, and allyl mustard oil. The very powerful odour of mustard oil is indeed evident after slightly moistening the seeds with water. The oil is obtained by distillation with water, and purified by further fractional distillation. It possesses the sp. gr. 1.017 at 10°, and boils between 150° and 151°; its vapour density is 3.4. It is insoluble in water, but mixes freely with alcohol and ether. The liquid raises blisters on the skin, and its vapour powerfully irritates the mucous membranes.

Synthetically it may be obtained by the reaction between C3H5I and potassium sulpho-cyanate in alcoholic solutions (difference from the alkyl mustard oils).

Ammonia forms with mustard oil
Allyl thio-urea, or thio-sinnamine:

S:C:N.CH2.CH:CH2 + NH3 =S:CN(CH2.CH:CH2)H

.NH2

which crystallises in colourless rhombic prisms, of bitter taste, melting at 74°, and soluble in water, alcohol, and ether. It combines with monobasic acids to acid, easily decomposable salts, and also gives compounds with metallic salts like mercuric chloride and silver nitrate.

Allyl pseudo-sulpho-cyanate combines with ethylamine to form allyl-ethyl thio-urea, (C3H5)HN.CS.NH.C2H,, a difficultly crystallisable syrup.

672. By heating an aqueous solution of sulph-allyl urea with plumbic oxide the sulphur is removed and allyl cyanamide formed (see § 276).

2

Allyl cyanamide is obtained as a syrupy mass after separating the lead from the solution by SH, and evaporating. It gradually changes or metamerises into triallyl melamine or sinnamine, C3N6(C3H5)3H3, which is soluble in water, alcohol, and ether, has a bitter taste, and reacts alkaline.

Allyl nitryl, CH2:CH.CH2.NO2, formed by the double decomposition between allyl iodide and argentic nitrite, is an oil heavier than water which boils at 96°.

Compounds of Glycerine.

673. The glycerine derivatives contain the same radical as the allyl compounds, but with single combination between the carbon atoms, so that it acts towards other radicals or elements as a trivalent group.

.

Either the triatomic alcohol glycerine or the compounds of allyl serve as raw material from which the glycerine compounds may be formed.

CH2.OH

Glycerine, C3H5(OH)3 = CH.OH

CH,.OH

674. The naturally occurring fats, both from plants and animals, are the neutral salts of the triatomic alcohol glycerine with the CnH2n-10.OH and the CnH2n-30.OH series of acids and a few others. As previously explained (§ 561), the fats are decomposed by boiling with strongly basic hydrates into the salts of the particular acids and glycerine (saponification).

If the alkalies are used as saponifying agents the glycerine can be obtained pure only with difficulty:

5

C3H5(OCnH2n-10)3 + 3KH0 = 3KO.CnH2n−10 + C2H¿(OH)3. In this case the mixture of soap and glycerine is neutralised with the proper amount of H2SO4, the fatty acid which separates removed mechanically, and the aqueous solution evaporated as far as possible. The residue is a mixture of alkaline sulphate and glycerine; the latter is removed by absolute alcohol, from which it is again obtained as a syrup on distilling off the alcohol. The saponification is much more conveniently made with plumbic oxide and water, whereby an insoluble lead salt is formed, from which the glycerine solution is filtered and a little dissolved lead removed by means of SH2. On the manufacturing scale glycerine is obtained by distillation of fats with superheated steam, producing insoluble fatty acid and pure glycerine. Glycerine can be obtained in several ways from allyl compounds, most conveniently by combining allyl bromide with bromine to form the tribromide, converting this by heating with silver acetate into glyceryl triacetate, which can be easily saponified into acetic salts and glycerine : C3H5Br2+3AgOC,H,O=3AgBr + C2H,(OC2H2O)3.

From propylene, and therefore from acetone and isopropyl alcohol, glycerine can be obtained by means of propylene dichloride.

The latter is converted, by heating with iodine chloride to 140°, into glycerine trichloride (§ 655), which further, by heating with much water to 170°, is converted into glycerine:

C3H5Cl2+3нOH + OH2 = C3H5(OH)3 + 3HCl + OH2. Small quantities of glycerine are also formed during the alcoholic fermentation of sugar. Consequently it is found in small quantities in such alcoholic beverages as are not distilled.

675. Glycerine in the ordinary condition is a syrupy liquid of very sweet taste; it can, however, by means of cold and simultaneous shaking, be obtained in fine crystalline masses.

It is soluble in water and alcohol, but scarcely in ether. By heating in open vessels to 170° it is rendered anhydrous, and then possesses the sp. gr. 1.27. It absorbs moisture from the atmosphere. Under ordinary pressure glycerine boils at 280°, with partial decom