Page:Encyclopædia Britannica, Ninth Edition, v. 5.djvu/578

566 CHEMISTRY [ORGANIC. = CH 5 . CN The most general method of obtaining the cyanides (nitriles) in a state of purity is the dehydration of the ammonium salts of acids containing the corresponding hydrocarbon radicles (see also p. 555). C 6 H 5 . CO(ONH 4 ) - 20H 2 Ammonium benzoate. Phenyl cyanide. Most of the other processes yield a mixture of cyanides and isocyanides : CH,I + KCN = CH 3 .CN + KI CH 3 I + AgCN = CH 3 .CN + Agl 1 Methyl iodide. Methyl cyanide. In the first of these methods the cyanide predominates, and in the second the isocyanide. By distilling a mix ture of potassium cyanide with an ethereo-metallic salt of sulphuric or sulphurous acid, a mixture of cyanide and isocyanide of the radicle contained in the ethereal salt is obtained, the cyanide or nitrile being in excess : CH 3 .KS0 4 + KCN = CH 3 .CN + K 2 SO 4 Methyl cyanide. KCN = C 10 H.CN KS0 Potassium-methylsulphate. C 10 H 7 .KSO 3 Potassium naphthylsulphite. Naphthyl cyanide. The cyanides or nitriles do not exhibit strongly marked basic properties, nor are they oxidized by Ag 2 O or HgO . They are not poisonous, and do not possess unpleasant odours. Their boiling-points are generally higher than those of the metameric isocyanides. The nitriles are sus ceptible of isomeric modifications depending on the iso- merism of their contained hydrocarbon radicles. IY. ETHERS. These compounds bear to the alcohols the same relations frhat the metallic oxides bear to the hydroxides : NaHO Na 2 O Ca"(HO).> Ca"0 CH 3 HO (CH 3 ) 2 C 2 H 4 "(HO) 2 C 2 H 4 "O Methyl alcohol. Methyl ether. Ethene alcohol. Ethene ether. In accordance with this view, many ethers are formed by dehydrating their corresponding alcohols by means of strong sulphuric acid, zinc chloride, boron trioxide, &c. : 2CH 3 HO - OH 2 = (CH 3 ) 2 Methyl alcohoL Methyl ether. 2C 7 H 7 .HO OH 2 = (C 7 H 7 ) 2 O. Benzyl alcohol. Benzyl ether. Conversely, many ethers, by prolonged heating with water, are retransformed into their corresponding alcohols. Oxygen being a diatomic element combines with two monatomic radicles. When the two radicles are similar the compound is termed a simple ether, when dissimilar a compound ether. Thus, the ethers formulated above (methyl and benzyl) are simple ethers ; while CH 3 .O.C 2 H 5 C 6 H n .O.CH 3 C 6 H 5 .O.C 3 H 5 Methyl-ethyl ether Methyl-amyl ether. Ptienyl-allyl ethe r. are examples of compound ethers. Compound ethers con taining a C n H 2n+1 and a C B H2_ 7 radicle are termed anisols. Ethers are liable to isomeric modifications dependent on the isomerism of their contained radicles, and likewise to metamerism depending on the presence of different radicles. For example, C 2 H 5 .O.C 4 H 9 (ethyl-butyl ether) would be metameric with (C 3 H 7 ) 2 O (propyl ether). A general method of preparing ethers (simple and com pound) containing monatomic radicles is to act upon the sodium derivative of the alcohol containing the one radicle with the haloid ether containing the other radicle. When the alcohol and haloid ether contain the same radicles, the result is a simple ether; when they contain different radicles a compound ether is produced : 1 The cyanide thus formed unites with AgCN, forming the compound CH 3 .CN , AgCN , which, on treatment with KCN in excess, yields the methyl isocyanide with the formation of KAg(CN) 2 . C 2 H 5 .NaO Sodium ethylate. C 2 H 5 .NaO C 2 H 5 I = (C 2 H 5 ) 2 Ethyl ether. CH 3 I = CH 3 O.C 2 H 5 Methyl-methyl ether. CH 3 I = CH 3 .O.C 6 H 5 Nal Sodium ethylate. C 6 H 5 .NaO + CH 3 I = CH 3 .O.C 6 H 5 + Nal Sodium phenate. Methyl-phenyl ether. The ethers derived from the phenols are prepared by special methods. Ethers containing diatomic radicles are obtained from the mono-haloid derivatives of the dihydric alcohols (glycols) by the action of KHO : C 2 H 4 C1(HO) + KHO = C 2 H 4 O + KC1 + OH 2 . Mouochlorhydiin. Ethene ether. Compound ethers can be obtained from the sodium derivatives of the glycols by the action of mono-haloid ethers : C 2 H 4 (NaO) 2 + 2CH 3 I = C 3 H 4 + 2NaI Sodium ethcnate. Ethene-dimethyl ether. The ethene series of ethers are more active in their chemical behaviour than those containing C n H 2n+1 radicles. Ethers corresponding to the first seven normal primary alcohols of the series C n H 2n+1 . HO are known. Of these "sulphuric ether" is most frequently met with. It is the oxide of ethyl (C 2 H 5 ) 2 O, and is prepared by allowing a stream of ethyl alcohol to flow into a mixture of strong sulphuric acid and alcohol kept at a constant temperature of about 140 C. The following reactions occur : C 2 H 5 HO + H 2 S0 4 = C 2 H 5 .HS0 4 + OH 2 Alcohol. Ethyl-hydrogen sulphate. C 2 H 5 .HS0 4 + C 2 H 5 HO = (C 2 H 5 ) 2 O + H 2 SO 4 . Ethyl-hydrogen sulphate. Ether. As will be seen from these equations, a given quantity of H 2 S0 4 is theoretically capable of etherifying an un limited quantity of alcohol ; practically, however, a limit is reached. If a mixture of alcohols is employed at starting, a compound ether is produced. Ethyl ether is a colourless, mobile liquid, but very slightly soluble in water, and possessing an agreeable odour. It boils at 35 5 C. By the action of chlorine it yields substitution derivatives, C 2 H 4 C1. 0. C 2 H 5 , .............. (C 2 C1 5 ) 2 0. V. SULPHUR, SELENIUM, AND TELLURIUM ALCOHOLS AND ETHERS. These compounds are the analogues of the alcohols and ethers (see p. 553), and are in many cases prepared by analogous methods. The following are typical reactions : C 2 H 5 C1 - Ethyl chloride. C 2 H 4 C1 2 Ethene dichloride. C 3 H 5 I + Allyl iodide. Preparation of Sulphur Alcohols. f KHS - Q 2 H 5 (HS) + KC1 Ethyi hydrosulphide. + 2KHS = C 2 H 4 (HS) 2 + C 7 H 7 C1 + Benzyl chloride. K(C 2 H 5 )S0 4 ^ Potassium ethyl-sulphate 2KC1 Ethene dihydrosulphide. KHS = C 3 H 5 (HS) + KI AJlyl hydrosulphide. KHS = C 7 H 7 (HS) + KC1 7 Benzyl hydrosulphide. KHS = C 2 H 5 (HS) Ethyl hydrosulphide. K 2 S0 4 2CH 3 C1 Preparation of Sulphur, &c., Ethers. + K 2 S - (CH 3 ) 2 S + 2KC1 Methyl chloride. Methyl sulphide. 2K(C 2 H 5 )S0 4 + K 2 Se = (C 2 H 5 ) 2 Se + 2K 2 S0 4 Potassium ethyl-sulphate. Diethyl selenide. Diethyl telluride is prepared by an analogous reaction, K 2 Te being substituted for K 2 Se. Polysulphides, (C 2 H 5 ) 2 S 2 , (C 2 H 5 ) 2 S 3 , can be obtained by employing alkaline poly- sulphides in these reactions. Certain thio-alcohols can be

prepared from the corresponding alcohols by the actiou