dichlor-glycid dibromide, CH,Br.CCI Br.CH2Cl, a liquid of sp. gr. and boiling point 221°. 2.1 By heating with six times its volume of sulphuric acid, and distillation of the product with water, it is converted into monochlor-acetone (§ 660). The process may be represented by the equa tions: 2 CH2: CC1.CH2Cl + HO.SO2.OH = CH3.CC1(O.SO2.OH).CH2Cl and CH3.CCI(O.SO2.OH).CH2Cl + H20 = H2SO4 + HCl Dibrom-glycid, CH2:CBr.CH,Br, or a-brom-allyl bromide, prepared from glyceryl tribromide and potassic hydrate, boils at 151°-152°. 768. When dibrom-glycid is heated with the salts of monobasic acids, it exchanges only one bromine atom-the terminal one-for the acid radical, and yields a-brom-allylic salts: 2 CH,:CBr.CH,Br + AgO.NO,= AgBr + CH,:CBr.CH,.0.NO. a-Brom-allylic nitrate, boils between 140° and 150°. CH2:CBr.CH,Br + KO.C2H2O= KBr+ CH2:CBr.CH2.O.C2H2O. a-Brom-allylic acetate, boiling point 163-164°. from which alkalies liberate a-brom-allylic alcohol, CH2: CBr.CH2.OH, as a colourless, mobile liquid of agreeable odour, sp. gr. 1.6 at 15° and boiling at 155°. Phosphoric chloride converts the alcohol into a-brom-allylic chloride, or chlor-bromglycid, CH2 : CBr.CH2Cl, which boils at 120°, and is also formed by the action of alkalies on glyceryl dichloro-bromide: CH2Cl.CHBr.CH,Cl (§ 682). Glyceryl dibromo-ethylate (§ 685), prepared from allyl-ethyl ether and bromine, is similarly converted by alkalies into a-bromallyl-ethyl ether, CH2:CBr.CH2.O.C2H5, a colourless liquid of agreeable odour, boiling at 130°-135°, of sp. gr. 1.26 at 12°. Dibrom-glycid also reacts with potassic sulphocyanate, forming a-brom-allyl sulphocyanate (comp. § 671), CH2: CBr.CH2.N: CS, which distils at about 200°, and with ammonia yields a-brom-allyl sulphurea, CH2:CBr.CH2.NH.CS.NH2, as crystals melting at 110°-111°. Symmetrical dichlor-acetone, CH2Cl.CO.CH,Cl (comp. § 760), can also be reckoned amongst the fully saturated derivatives of isallylene. It is obtained by oxidation of dichlorhydrin (§ 679, 2) with chromic and sulphuric acids, and occurs amongst the products of direct chlorination of acetone. It crystallises in colourless rhombic tables, melts at 43°, and boils at 172°-174°. Homologues of Isallylene. 769. Several hydrocarbons behave quite similarly to isallylene as regards their inability to precipitate ammoniacal silver and cuprous compounds, and can therefore be regarded as homologous to it. Crotonylene, C4H6 = CH3.CH:C:CH2, occurs in coal gas, and GG can be separated therefrom in the liquid form by pressure. It is obtained, similarly to acetylene and allylene, by heating brom-butylene (§ 661) with alcoholic potassic hydrate: CH3.CH2.CBr: CH2 + KOH = KBr + H2O + CH3.CH: C:CH2, and by passing a mixture of equal volumes of acetylene and ethylene through a tube heated to dull redness: CH2: CH2+CH CH CH3.CH: C: CH2. 2 It is a colourless liquid boiling at 20°, which unites with bromine, forming a liquid dibromide, C,H,Br2, boiling at 150°, and a crystalline tetrabromide, CH3.CH Br.CBr2.CH2Br. 6 Isovalerylene, CH, = (CH3)2C: C:CH2, is formed from bromisoamylene (§ 701) by alkalies. It is a liquid of garlic odour which boils between 42° and 45°. It yields only liquid compounds with bromine ; namely, a dibromide, C,H,Br2, boiling at 170°, and a tetrabromide, CH,Br, or (CH3)2: CBr.CBr2.CH,Br, which cannot be distilled unchanged. Some higher hydrocarbons of the series CnH2n2 have been prepared in similar manner from the monohalogen olefines, but require more investigation; e.g. hexoylene, C6H10, distilling between 76° and 80°. DERIVATIVES OF THE TETRHYDRIC ALCOHOL RADICALS. Erythrite, C,H(OH), = CH2(OH).CH(OH).CH(OH).CH2(OH). 770. This tetrhydric alcohol, also termed erythro-glucin or phycite, occurs in Protococcus vulgaris, and is formed by decomposition of erythrin (contained in several lichens, e.g. Rocella Montagnei) by boiling with lime or baryta water. The lichens are best boiled with milk of lime; the excess of lime in solution is then removed by passing carbonic anhydride, the filtrate evaporated to a thin syrup and treated with alcohol. After some time erythrite crystallises out, and can be purified by recrystallisation from boiling alcohol. Orcin and orsellenic acid are found in the alcoholic mother liquors. Erythrite forms large colourless prismatic crystals, which dissolve readily in water, difficultly in cold alcohol, and are insoluble in ether. It tastes sweet, melts at 120°, and volatilises with partial decomposition at about 300°. Potassic hydrate at 250° decomposes it into oxalic and acetic acids: C ̧H¿(OH) + 3KOH = K2C20 ̧ + KC2H ̧O + H2O + 4H2. By heating with acids salts are obtained. The nitrate termed nitro-erythrite, CH(O.NO2), is formd by solution of erythrite in concentrated nitric acid, and precipitates on addition of concentrated sulphuric acid in colourless crystalline leaves. It melts at 61° and explodes violently when struck. Hydriodic acid converts erythrite into normal secondary butylic iodide ($ 193); by long heating with hydrochloric or hydrobromic acids it exchanges two OH groups for halogen, yielding dihydrate dihaloids of its radical, which are converted into dihaloid dinitrates by a mixture of sulphuric and nitric acids. 6 Erythrite dichlorhydrin, C,H,Cl2(OH)2, forms colourless crystals readily soluble in water, alcohol, or ether, and melts at 145°. Nitro-erythrite dichlorhydrin, C4H6.Cl2(O.NO2)2, crystallises in needles, melts at 60°, and is not explosive. Erythrite dibromhydrin, C4H6Br2(OH)2, melts at 130° and yields a nitrate, C,H,Bra(O.NO2)2, crystallising in brilliant needles and melting at 70°. 6 771. By heating erythrite with formic acid a monoformate is first formed, which (similarly to the decomposition of the monoformin of glycerine into allylic alcohol) decomposes between 220° and 240° into carbonic anhydride, water, and erythro-glycol : C,H,(OH),(O.CHO)=CO, + H,O + C,H,(OH),. Erythro-glycol. Erythro-glycol contains two hydrogen atoms less than butylene glycol, and probably has one of the formulæ : CH2 : CH.CH(OH).CH2.OH or CH2.(OH).CH: CH.CH2(OH). It is a thick liquid, soluble in water, boiling at 199°-200°, and unites directly with two atoms of bromine. In its preparation there is also formed--without doubt from an erythrite diformate-a hydrocarbon isomeric with crotonylene, and which probably may be the isolated radical of erythrite: It unites with bromine to form a tetrabromide, giving brilliant leafy crystals, melting at 115°-116° : CH,Br.CHBr.CH Br.CH,Br (?). Diallyl, C6H10 CH2:CH.CH2.CH2.CH:CH2. = 772. Diallyl is formed by treatment of allyl haloids with metals. Allylic iodide or bromide is generally used, and is heated with sodium after addition of a drop of ethylic alcohol: 2C2HI+Na, = 2NaI + C6H10 Finely divided silver acts in the same way at 100°. Another method consists in heating mercury allyl iodide (§ 664) with a solution of potassic cyanide : 21.Hg.C3H5 + 2KCN = 2KI + Hg(CN)2 + Hg + C6H10. Diallyl is a colourless, mobile liquid of sp. gr. 864, which boils at 59° and has a vapor density: = 2.83. It unites with bromine to form a crystalline tetrabromide, melting at 63°, and with hydriodic acid to form the compounds C6H11I and C6H12I2, already mentioned (§§ 702 and 491, 2). DERIVATIVES OF THE PENTAVALENT HYDRO- DERIVATIVES OF THE RADICALS OF DISUBSTITUTED FATTY ACIDS. 773. Whilst the replacement of one hydrogen atom in the radical of a fatty acid yields compounds of the glycollic acid group only, the replacement of two hydrogen atoms can lead to several categories of bodies. 1. If the substitution occur on a single carbon atom it may occur a. On a terminal carbon atom. The simplest oxides must be at once aldehydes and acids. b. On an intermediate carbon atom. There then result derivatives of the ketonic acid radicals. 2. The substitution may occur on two different carbon atoms. There are then formed the derivatives of the double alcohol acid radicals. If the removal of the hydrogen atoms is from neighbouring carbon atoms, double union may ensue. The acids of this kind form the acryl crotonic acid series. Derivatives of Aldehyde Acid Radicals. At present compounds of the nucleus CH.CE, ethinyl, and some aldehyde acids richer in carbon are known. Compounds of Ethinyl, CH C= 774. Halogen Compounds. These have been to some extent already mentioned in speaking of ethylene and acetylene. In the first place there belongs to this group the substitution products of acetylene, including the metallic derivatives already mentioned (§ 752). Ethinyl bromide, C2HBr CH CBr, or brom-acetylene, is obtained, together with acetylene, by the decomposition of bromethylene dibromide (§ 650) by boiling alcoholic potassic hydrate: CH,Br.CHBr, + 2KOH=2KBr + 2H,O + CH:CBr. It has not yet been prepared in the pure state, and is therefore little known; it is characterised by its spontaneous inflammability in air. Ethinyl trichloride, trichlor ethylene, CHC1: CC12, is prepared from acetylene tetrachloride by action of alcoholic potassic hydrate, and is an oil boiling at 88°. The corresponding ethinyl tribromide, CHBr:CBr2, is also liquid, boils at 130°, and after some time changes into a polymeric non-volatile substance. Ethinyl pentahaloids are prepared from the foregoing by addition of chlorine and bromine, further from the tetrahaloids of glycolyl ($ 708) and acetylene (§ 752) by direct substitution: CH,C1.CC13+ Cl2 = HCl + CHC12.CC13 and CHC12.CH.Cl2+ Cl2 = HCl + CHC12.CC13. Ethinyl pentachloride, trichlor ethylene dichloride, is a colourless oil of sp. gr. 16, which boils at 158°. Ethinyl pentabromide crystallises in long prisms, which melt between 48° and 50°. Ethinyl tetrachloride ethylate is the tetrachlor ether obtained by direct chlorination of ether. It is liquid and boils at 1890-190° with partial decomposition. 775. Chloral, C2HC1 ̧O = CC13.CHO. This trichlor acetic aldehyde is formed by the action of chlorine on aldehyde, alcohol, sugars, and some other compounds. It is obtained most readily by passing dry chlorine into absolute alcohol to complete saturation. Considerable quantities of ethylic chloride and its chlor-substitution products volatilise with the hydrochloric acid formed according to the equation : CH..CH..OH + 4C1, = 5HC1 + CC1,.CHO + Finally a crystalline mass remains, consisting principally of a compound of chloral with alcohol, CC13.CH(OC,H,)(OH), and some chloral hydrate, CC13.CH(OH)2, which on distillation with concentrated sulphuric acid yields pure chloral. Chloral is a mobile, colourless liquid of penetrating odour and sp. gr. 1-502, which boils at 94.5°. On keeping it is transformed into a white, porcelain-like mass of the polymeric parachloral, probably trichloral, which distils at 180°, being then reconverted into ordinary chloral. Chloral is a true aldehyde, and is therefore converted by oxidation -best with concentrated nitric acid-into trichlor acetic acid, unites with alkaline hydric sulphites to form crystalline compounds, yields, on heating with acetic anhydride to 150°, trichlor ethylidene diacetate, CC13.CH(OC,H3O)2, a clear oil boiling at 222°; it unites directly with acetylic chloride, forming trichlor ethylidene aceto-chloride, CC13.CHCI(O.C2H,O), which boils at 185°. With ammonia and the alkylamides it yields hydratamides of trichlor ethylidene, e.g. as solid, fusible masses. Phosphoric chloride converts it into ethinyl pentachloride, and nascent hydrogen in acid solution (zinc and hydrochloric acid) reconverts it into acetic aldehyde. Chloral is distinguished from acetic aldehyde, on the one hand, by the greater energy of its union with water, and from alcohol (comp. § 384), on the other, by the more ready disruption of its carbon nucleus. Chloral unites with water with considerable evolution of heat forming |