801. Doglic acid, C19H36O2, from the oil from the dægling or bottle-nosed whale, melts at 16°.

Erucic acid, C22H4202, also called brassic acid, is obtained from rape-seed oil, mustard oil, and also from grape seeds or kernels. It is purified by means of its lead salt in similar manner to that already described for other members of the series. It forms long shining needles melting at 34°. With bromine it gives a dibromide, C22H42Br2O2, forming warty crystals melting at 42°-43°, decomposed by alcoholic potassic hydrate into brom-erucic acid, C22H41 BrO 2, fusing at 33°-34°.`

Dihydroxy-acids, CnH2n-3(OH)20.OH.

802. The only known member of this series is glyceric acid, dihydroxy-propionic acid, C3H604, the product of the gentle oxidation of glycerine by nitric acid or by bromine and water.

For its preparation a mixture of equal parts of glycerine and water contained in tall glass cylinders is very slowly mixed with double its volume of nitric acid, of sp. gr. 13, by means of a long funnel tube reaching to the bottom of the liquid. After standing a few days, until the liquid has become homogeneous, it is evaporated to a syrup, which is then diluted with water and neutralised with plumbic carbonate. After several recrystallisations and treatment with animal charcoal the pure salt is decomposed by hydric sulphide. The filtrate, on evaporation, yields the free acid as a syrup.

Its salts are mostly soluble and crystallisable. The calcic salt, (C3H5O4)2Ca + 20H2, crystallises in concentrically grouped prisms. The ethylic salt, C3H5(C2H5)O, is a viscid liquid, boiling at 230°-240°, sp. gr. 1.193 at 6°, soluble in water, and easily decomposing into free acid and alcohol.

Glyceric acid is a monobasic acid and also a diatomic alcohol, and possibly has the constitution CH2(OH).CH(OH).CO.OH, but the process of oxidation and constitution may also be expressed by the following equation:

On heating to 140° the acid gives a gummy substance, which is probably an ethereal anhydride (§ 707). At a higher temperature it gives off more water, and passes for the most part into pyro-racemic or pyruvic acid with a little pyro-tartaric acid:

Treated with hydriodic acid it gives glycerine iodo-propionic acid (§ 744); with phosphoric chloride, the chloride of B-dichlor-propionic acid:

C3H6O1 + PC13 = 3POCl3 + 3HCl + C2HзCl2O.C1.

4

Boiling potassic hydrate solution converts glyceric acid into oxalate and lactate. Melted potash gives acetate and formate.

It is a Sombi mbete with water and being between 145a and 170". decxcmposing, however, digirly thing declatie Is moobasie mits are crystallisatie, but lose this property on warming their

The acid cannot be obtained unchanged in scififying its salts, but is eonverted into a syrupy non-volatile acil giving pro-tartaric seid on deflatica

Nascent kylmogen envers it into celinary lactic acid, and by heating with by irie tolle either lactic or propionic acid may be produced, according to the temperature or relative quantities employed: CH2

CH2

With bromine it forms an extremely unstable crystalline compound, C,H,Br0, At a temperature of 100 bromine gives a From-pyroracemic acid, C2H.Br.0, +20H,, which forms large rhombic crystals. Phosphoric chloride converts it into dichlor propionic chloride. By long hesting with baric hydrate solution saits of acetic, oxalic, and nitric acids are produced.

Propionyl formic acid, CH,CH,CO.CO.OH, is a colourless oily liquid, of sp. gr. 1-12 and boiling at 74-78 under a pressure of

25 mm.

Butyryl formic acid, CH,CH,CH,CO.CO.OH, is a colourless liquid, iling with slight decomposition at 180-185° under ordinary atmospheric pressure.

Serine, sericine, C2H,NO,, is related to glyceric acid in the same manner that glycocine is to glycolic acid or alanine to lactic acid. It is a product of the decomposition of silk by boiling dilute sulphuric acid.

Serine crystallises in hard prisms, soluble in cold water, but insoluble in alcohol. It has a faintly sweet taste, and behaves towards acids and bases like a glycine (§ 718); e.g. it combines one equivalent of an acid and allows one hydrogen atom to be replaced by a metal. Its salts are all crystallisable.

Nitrous acid converts it into glyceric acid :

C2H2(OH)(NH2)O.OH + HO.NO = H2O + N2
+ C2H2(OH)2O.OH.

Cystine, CH,NO,S, appears to be a sulphur derivative of serine. It has been found in urine and in the kidneys in very small quantity ; in larger quantity in some forms of urinary calculi, from which it may

be extracted by ammonia solution and obtained in minute colourless six-sided tabular crystals.

It is insoluble in water and alcohol, but dissolves in alkalies and acids, forming crystalline salts with the latter. It is non-volatile, and decomposes on heating with production of a most penetrating odour.

PROPARGYL COMPOUNDS.

804. By removal of two hydrogen atoms from allyl and substitution of a triple for a double carbon union, the primary radical propargyl is formed. The propargyl compounds therefore appear as allyene (§ 759), in which one hydrogen atom of the methyl group has been replaced by halogens or oxygen nuclei, &c. :

=

805. Propargylic alcohol, C3H40 CH C.CH2.OH, is obtained from a-brom-allylic alcohol (§ 768) by heating with potassic hydrate and a little water in a vessel attached to an inverted condenser:

CH2:CBr.CH2.OH + KOH = KBr + H2O + CHC.CH,.OH.

The excess of potassic hydrate is neutralised with carbonic anhydride, and the aqueous propargylic alcohol distilled off; potassic carbonate added to the distillate to saturation, the separated lighter layer removed, dried by fused potassic carbonate and rectified.

Propargylic alcohol is a colourless mobile liquid of burning taste and agreeable smell, miscible with water. Its sp. gr. is 9628 at 21°, the vapour density 19; it boils at 115°. The vapour burns in air with a strongly luminous flame. It yields a siskin-green precipitate with ammoniacal cuprous chloride, which burns explosively on heating, and probably has the formula:

Cu.CC.CH.OH

Cu.CC.CH2.OH
C: C.CH

Ammoniacal argentic chloride gives a white precipitate of analogous composition, Ag2(C:C.CH2.OH)2. Both metallic compounds yield propargylic alcohol when treated with hydrochloric acid. It combines directly with bromine, and with strong hydrobromic acid regenerates a-brom-allylic alcohol.

It reacts on phosphorus tribromide, forming propargylic bromide, CH C.CH2Br, a colourless liquid of sp. gr. 1.52 at 20° and boiling at 88°-90°, whilst acetylic chloride converts it into propargylic acetate, CH C.CH2.O.C2H2O, a liquid of unpleasant odour, boiling at 125°. Propargyl-ethyl ether, C,H,O=CH C.CH2.O.C,H5, is obtained when alcoholic potassic hydrate acts on glyceryl trihaloids :

=

CH,CI.CHCI.CH,Cl + 2KOH + KOC2H, 3KCl + 2H2O + CHC.CH2.O.C2H, (comp. § 197),

on allylene dibromide ($759):

CHBr:CBr.CH, + KOH + KOC,H,= 2KBr + H,O
+CH C.CH.O.C2H5,

on dichlor glycid (§ 767):

CH2:CCI.CH2Cl + KOH + KOC2H5 = 2KCl + H2O
+CH C.CH2.O.C2H5,

and on brom-propylene dibromide (§ 659). It is a colourless liquid of disagreeable, penetrant odour, of boiling point 81°-82° and sp. gr. 83 at 7°. It gives a yellow precipitate with ammoniacal cuprous chloride, Cu2(C: C.CH2.O.C2H)2, and a white in ammoniacal argentic nitrate of Ag(C C.CH2O.C2H3)2.

473

DERIVATIVES OF THE HEXAVALENT HYDROCARBON NUCLEUS, CnH2n-1

MONOBASIC UNSATURATED ACIDS.

806. Although the first substitution products of the acids CnH2n-202 (§792), and also ricinolic acid (§ 800), are monobasic acids of this group, it has been more convenient to consider them at another place.

COMPOUNDS OF THE DOUBLE ACID RADICALS, CnH2n': (C)2.

807. The chief representatives of this group are the dibasic acids and the derivatives of their oxy-radicals, the diacidoxyls, CnH2n (CO) 2. The only compounds known free from oxygen are some nitriles and a number of varied derivatives of the dicarbon nucleus C.C.

The dibasic acids stand to the monobasic acids in the same relation as the glycols to the monhydric alcohols. All metamorphoses of the monobasic acids can be suffered by them either singly or doubly. Thus they form two series of salts:

M representing either a metal or alkyl, &c., normal and acid amides :

CnH2n' CO.NH2
.CO.NH,

together with salts of the latter.

The formation of anhydrides and imides probably occurs in a different way to that in the fatty acids, the anhydro-oxygen atom or divalent imid group not being attached to two diacid oxyls, but to both bonds of a single diacid oxyl :

.CO

.CO

CnH2n CO O, anhydride, and CnH2n CO NH, imide.

808. Formation of Dibasic Acids. The dibasic acids can be prepared by oxidation of the double primary glycols, e.g.