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AMINES

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Originally appearing in Volume V01, Page 858 of the 1911 Encyclopedia Britannica.
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AMINES , in See also:

chemistry, derivatives of See also:ammonia in which one or more of the See also:hydrogen atoms are replaced by alkyl or aryl See also:groups. The replacement of one hydrogen See also:atom by one alkyl or aryl See also:group gives rise to See also:primary amines; of two hydrogen atoms by two groups, to secondary amines; of three hydrogen atoms by three groups, to See also:tertiary amine's. The tertiary amines possess the See also:power of combining with one molecular proportion of an alkyl iodide to See also:form See also:quaternary ammonium salts. The structural relations of these compounds may be shown thus: NH3; NH2R; Ammonia; primary amine; NHR2; NR3; NR4I. secondary amine; tertiary amine; quaternary ammonium iodide. Aliphatic amines.—These compounds possess properties very similar to those of ammonia, the lowest members of the See also:series being combustible gases readily soluble in See also:water. The next higher members of the series are liquids of See also:low boiling point also readily soluble in water, the solubility and volatility, however, decreasing with the increasing See also:carbon content of the See also:molecule, until the highest members of the series are odourless solids of high boiling point and are insoluble in water. They are 'all strongbases, readily forming salts with the See also:mineral acids and See also:double salts with the chlorides of See also:gold, See also:platinum and. See also:mercury. They are ionized in aqueous See also:solution to a much greater extent than ammonia, the quaternary ammonium bases being the most ionized, and the secondary bases being more strongly ionized than the primary or tertiary bases. For data concerning the conductivity of the organic bases see G. Bredig (Zeit. See also:fur phys. Chem., 1894, 13, p.

289). Many methods have been devised for the preparation of the amines, the first amine having been isolated in 1849 by A. See also:

Wurtz on boiling methyl isocyanate with See also:caustic potash, CON•CH3+ 2KHO=CH3NH2+K2CO3. The primary amines may also be prepared by See also:heating the alkyl iodides with ammonia (A. W. See also:Hofmann) ; by the reduction of nitriles with See also:alcohol and See also:sodium (A. Ladenburg, Ber., 1886, 19, p. 783); by heating the See also:esters of nitric See also:acid with alcoholic ammonia at loo° C. (0. Wallach, Ber., 1881, 14, p. 421); by the See also:action of reducing agents on nitro paraffins; by the action of See also:zinc and hydrochloric acid on aldehyde ammonias (See also:German Patent 73,812); by the reduction of the phenylhydrazones and - See also:oximes of See also:aldehydes and See also:ketones with sodium See also:amalgam in the presence of alcohol and sodium acetate (J. Tafel, Ber., 1886, 19, p.

1925; 1889, 22, p. 1854; H. See also:

Goldschmidt, Ber., 1886, 19, p.- 3232); by the action of dilute hydrochloric acid on the isonitriles, R•NC+2H2O=R•NH2±H2CO2; by heating the See also:mustard See also:oils with a mineral acid, by the See also:hydrolysis of the alkyl phthalimides (S. -See also:Gabriel, Ber., 1887, 20, p. 2224; 1891, 24, p. 3104), O RI CO 2H2O See also:COON CeH,<C ~NK - See also:C6H4< >NR –> C6H4< +NH2R; CO CO COOH by distilling the amino-acids with baryta; by the action of See also:bromine and caustic potash on the acid-amides (A. W. Hofmann, Ber., 1885, 18, p. 2734; 1886, 19, p. 1822); CH3CONH2-4CH3CONHBr--CH3CONKBr–> CH3NCO–CH3NH2' and by the hydrolysis of substituted urethanes (Th. See also:Curtius, See also:Bert, 1894, 27, p. 779; 1896, 29, p.'1166), N2H4•H20 HONO R•COOH–~R•COOR' –~--> R.See also:CONH .See also:NH2 acid ester hydrazide C2H5OH HCI R.CON3 –~ R•NH•CO2C2H5 R.NH2 azide See also:urethane The secondary amines are prepared, together with the primary and tertiary, by the action of ammonia on the alkyl iodides (see below), or by the hydrolysis of See also:para-nitroso derivatives of tertiary aromatic amines, such as para-nitrosodimethylaniline, thus: NO•C6H4•N(See also:CH3)2 + See also:H2O = NO•C6H4.OH + NH(CH3)2.

By the action of ammonia-en the alkyl iodides a complex mixture of primary, secondary and tertiary amines, along with a quaternary ammonium See also:

salt, is obtained, the separation of which is difficult. The method worked out by A. W. Hofmann is as follows:—the mixture is distilled with caustic potash, when the primary, secondary and tertiary amines distil over, and the quaternary ammonium salt remains behind unaffected. The aqueous solution of the amines is now shaken up with diethyl oxalate, when the primary amine forms a crystalline dialkyl oxamide and the secondary amine an insoluble liquid, which is an See also:ethyl dialkyl oxamate, the tertiary amine not reacting: (CO2C2H5)2+ 2NH2R = (CO'NHR)2 + 2C2H5OH; (CO2C2H5)2 + NHR2 C2H5O2C•CONR2+C2H5OH. The tertiary amine is then distilled off, the residual products separated by filtration and finally hydrolysed by a caustic See also:alkali. • The primary, secondary and tertiary amines may be readily dis- tinguished by their behaviour with various reagents. Primary amines when heated with alcoholic potash and See also:chloroform yield isonitriles, which are readily detected by their offensive See also:smell. The secondary and tertiary amines do not give this reaction. With nitrous acid, the primary amines yield See also:alcohols, the secondary amines yield nitrosamines and the tertiary amines do not react: R•NH2+ONOH =R•OH+N2+H2O; R2NH+ ONOH=R2N•NO+H20. With See also:benzene sulphochloride in the presence of alkali, the primary amines yield compounds of the type C6H5S02NHR, soluble in alkalies, whilst the secondary amines yield compounds of the type C6H5SO2NR2, insoluble in alkalies (0. Hinsberg, Ber., r89o, 2-3, p.

2963). Primary amines heated with carbon bisulphide in alcoholic solution are converted into mustard oils, when the dithiocarbamate first produced is heated with a solution of mercuric chloride. Methylamine, CH3NH2, occurs in Mercurialis perennis, in See also:

bone-oil, and See also:herring brine. It is also a decomposition product of many alkaloids. At See also:ordinary temperatures it is a See also:gas, but may be condensed to a liquid which boils at - 6° C. It has a strong ammoniacal smell, See also:burns readily and is exceedingly soluble in water. its See also:critical temperature is 1550 C. and critical pressure 72 atmos. (C. See also:Vincent, J. Chappuis; Jahresb., 1886, p. 202). Dimethylamine, (CH3)2NH, is found in Peruvian See also:guano. It is a heavy vapour which condenses at 7° C. to a liquid, having a pronounced See also:fish-like smell.

Trimethylamine, (See also:

CH8)3N, is very similar to dimethylamine, and condenses to a liquid which boils at 3.2-3.8° C. It is usually obtained from " vinasses," the See also:residue obtained from the See also:distillation of See also:beet See also:sugar alcohol, and is used in the manufacture of See also:potassium bicarbonate by the Solvay See also:process, since its hydrochloride is much more soluble than potassium carbonate. Tetramethylammonium iodide, N(CH8)4I, is the See also:chief product obtained by the action of methyl iodide on ammonia (Hofmann). It crystallizes in quadratic prisms and has a See also:bitter See also:taste. By warming its aqueous solution with an excess of See also:silver See also:oxide it is converted into tetramethylammonium hydroxide, N(CH3)4OH, which crystallizes in hygroscopic needles, and has a very alkaline reaction. It forms many crystalline salts and absorbs carbon dioxide. It precipitates many metallic hydroxides. On dry distillation it is resolved into trimethylamine and methyl alcohol. If the See also:nitrogen atom in the quaternary ammonium salts be in See also:combination with four different groups, then the molecule is asymmetrical, and the salt can be resolved into optically active enantiamorphous isomerides. W. J. See also:Pope (Jour.

Chem. See also:

Soc., 1901, 79, p. 828) has resolved benzyl-allyl-phenyl-methylamine iodide by boiling with silver d-camphorsulphonate in a nearly anhydrous mixture of See also:acetone and ethyl acetate. The silver iodide is separated and ,the solvent distilled off. The residue crystallizes slowly, and the crystalline product is almost wholly d-benzyl-allyl-phenyl-ammonium-d-sulphonate, the corresponding 1-See also:compound remaining as a syrupy residue. The corresponding iodides are obtained by the addition of potassium iodide to solutions of the sulphonates, and are optically active See also:antipodes. Diamines.—The diamines contain two amino groups and See also:bear the same relation to the See also:glycols that the primary monamines bear to the primary alcohols. They are of importance, since the higher homologues are identical in many cases with the ptomaines produced by the putrefactive action of some bacteria on albumen and other related substances. See also:Ethylene diamine, C2H4(NH2)2, may be prepared by heating ethylene dibromide with alcoholic ammonia to 1oo° C. (F. S. Cloez, Jahresb., 1853, p..468); or by the action of See also:tin and hydrochloric acid on See also:cyanogen (T.

Fairley, See also:

Ann. Suppl., 3, 1864, p. 372). It is an alkaline liquid, which when anhydrous boils at 116.5° C. Nitrous acid converts it into ethylene oxide. It combines directly with many metallic salts. (See S. F. Jorgensen, Jour. pr. Chem., 1889 (2), 39, p. 8.) Trimethylene diamine, NH2.(See also:CH2)3.NH2, is prepared by the action of ammonia on trimethylene bromide (E. See also:Fischer, Ber., 1884, 17, p.

1799). It is a liquid which boils at 135-136° C., and is readily soluble in alcohol, See also:

ether, chloroform and benzene. Tetramethylene diamine (putrescine), NH2.(CH2)4•NH2, is prepared by reducing ethylene dicyanide (succinonitrile) with sodium in See also:absolute alcoholic solution (A. Ladenburg, Ber., 1886, 19, p. 78o). It melts at 27° C., and is easily soluble in water. Pentamethylene diamine (cadaverine), NH2•(CH2)5.NH2,is prepared by reducing trimethylene See also:cyanide in ether solution by zinc and hydrochloric acid (A. Ladenburg, Ber., 1883, 16, p. 1151). J. V. Braun (Ber., 1904, 37, p.

3583) has prepared pentamethylene derivatives from piperidine by the action of See also:

phosphorus pentachloride. On See also:heat-. See also:ing piperidine with phosphorus pentachloride to 2oo°C. in a sealed See also:tube pentamethylene dichloride is obtained, and this on treatment with potassium phthalimide gives a condensation product of See also:composition, C6H4[CO]2N(CH2)5N[CO]2C6H4, which is finally85.7 hydrolysed by hydrochloric acid. Cadaverine is a See also:syrup at ordinary temperatures, and boils at 178-179° C. It is readily soluble in water and alcohol, but only slightly soluble in ether. Aromatic Amines.—The aromatic amines in some respects resemble the aliphatic amines, since they form salts with acids, and double salts with platinum chloride, and they also distil without decomposition. On the other See also:hand, they are much weaker bases than the aliphatic amines, their salts undergoing hydrolytic See also:dissociation in aqueous solution. The primary aromatic amines may be prepared by the reduction of the nitro-See also:hydrocarbons, the reducing agents used being either alcoholic-ammonium sulphide (N. Zinin), zinc and, hydrochloric acid (A. W. Hofmann), an alcoholic solution of stannous chloride (containing hydrochloric acid) (R. Anschutz, Ber., 1886, 19, p. 2161), tin and hydrochloric acid, or, on the manufacturing See also:scale, See also:iron and hydrochloric acid.

They may also be obtained by the reduction of,nitroso compounds and of hydrazo compounds and of hydrazones (J. Tafel, Ber., 1886, 19, p. 1924), by distilling the amido-acids with See also:

lime, by heating phenols with zinc chloride ammonia (V. Merz, Ber., 188o, 13, p. 1298), and by heating the secondary and tertiary bases with concentrated hydrochloric acid to about ,8o° C. At a temperature of about 300-400° C. the alkyl chloride formed in this reaction attacks the benzene See also:nucleus and replaces hydrogen by an alkyl group or groups, forming primary amines homologous with the See also:original amine; thus methylaniline hydro-chloride is converted, into para- and ortho-toluidine hydro-chloride, and trimethyl phenyl ammonium iodide is converted into mesidine hydriodide. It is to be noted that only traces of the aromatic amines are produced by heating the halogen substituted benzenes with ammonia, unless the amino group be situated in the See also:side See also:chain, as in the See also:case of benzylamine. The primary amines are colourless liquids or crystalline. solids, which are insoluble in water, but readily soluble in the See also:common organic solvents. When heated with alkyl or aryl iodides, they are converted into secondary and tertiary amines. Concentrated nitric acid attacks them violently, producing various oxidation products, but if the amino group be " protected " by being previously acetylated, then nitro derivatives are obtained. When heated with concentrated sulphuric acid for some See also:time, they are sulphonated. They form condensation products with aldehydes, See also:benzaldehyde and See also:aniline forming benzylidene aniline, C6H5N: CHCeH5, and when heated with acids they form anilides.

They give the isonitrile reaction (see above): when warmed with chloroform and a caustic alkali, and form alkyl thioureas when heated with an alcoholic solution of carbon bisulphide. When warmed with a solution of nitrous acid, they are converted into phenols; if, however, nitrous acid be added to an See also:

ice-See also:cold solution of a primary amine in excess of mineral acid, a diazonium salt is formed (see See also:Azo COMPOUNDS and DIAzO COMPOUNDS), or in See also:absence of excess of acid, a diazoamine is produced. The secondary amines may be of two types—namely,the purely aromatic amines, and the mixed secondary amines, which contain an aromatic residue and an alkyl group. The purely aromatic amines result upon heating the primary amines ' with their hydrochlorides, and, in some cases, by heating a phenol with a primary amine and anhydrous zinc chloride. The mixed secondary amines are prepared by the action of alkyl iodides on the primary amines, or by heating salts of the primary amine with alcohols under pressure. The mixed secondary amines have basic properties, but the purely aromatic secondary amines are only very feeble bases: Both classes readily See also:exchange the imide hydrogen for acid radicals, and give nitrosamines with nitrous acid. The secondary amines do not give the isonitrile reaction. The tertiary amines may also be of two types, the purely aromatic and the mixed type. The mixed tertiary amines are produced by the action of alkyl halides on the primary amines. The simplest aromatic tertiary amine, triphenylamine, is prepared by the action of brombenzene on sodium diphenylamine (C. Heydrich, Ber., 1885, 18, p. 2156).

The simplest aromatic monamine is aniline (q.v.), and the simplest mixed amines are mono- and di-methyl aniline. These substances are treated in the See also:

article ANILINE. The aromatic amine resembling the aliphatic amines is benzylamine, C6H5•CH2•NH2, which may be prepared by reducing benzonitrile in alcoholic solution by means of zinc and acetic acid (O. Mendius, Ann. 1862, 121, p. 144), or by metallic sodium (E. See also:Bamberger, Ber., 1887, 20, p. 1709). It can also be obtained by the action of ammonia on benzyl chloride (S. See also:Cannizzaro, Ann., 1865, 134, p. 128), but di- and tri-benzylamines are simultaneously formed. It is a liquid, which boils at 183° C., and is miscible in all proportions with water, alcohol and ether.

It is basic in See also:

character, and has a strongly alkaline reaction. Diphenylamine, (See also:C6H5)2NH, is the simplest representative of the true aromatic secondary amines. It is prepared by heating aniline and aniline hydrochloride for some See also:hours to 210-240° C, (Ch. See also:Girard and G. de Laire, Zeit fur. Chem., 1866, p. 438). It crystallizes in See also:white plates, which melt at 45° C. and See also:boil at 302° C. It is almost insoluble in water, but readily volatilizes in See also:steam. When heated with monobasic saturated acids and zinc chloride it yields acridines. Aromatic Diamines.—The diamines are prepared by reducing the nitranilines or the dinitrohydrocarbons. They crystallize in plates, and for the most See also:part distil without decomposition. Orthophenylene diamine, CsH4 (NH2)2, crystallizes from water in plates, which melt at 102-103° C. and boil at 256-258° C.

When heated with 10 % hydrochloric acid to 18o° C. it yields See also:

pyrocatechin (See also:Jacob See also:Meyer, Ber., 1897, 30, p. 2569). The orthodiamines are characterized by the large number of condensation products they form. (See IMmAZOLES, QUINOXALINES, &c.). Metaphenylene diamine crystallizes in rhombic plates which melt at 63° C. and boil at 287° C. It is easily soluble in water and alcohol. When heated with To % hydrochloric acid to 18o° C. it yields See also:resorcin (J. Meyer). Paraphenylene diamine may be prepared as above, and also by the reduction of amidoazobenzene. It crystallizes in tables which melt at 140° C. and boil at 267° C. When heated with 10 % hydrochloric acid to 18o° C. it yields hydroquinone (J. Meyer).

See also:

Manganese dioxide and dilute sulphuric acid oxidize it to quinone. The three classes of diamines may be distinguished by their behaviour towards nitrous acid. The ortho-compounds condense to azimido benzenes, the See also:meta-compounds yield azo-dyestuffs, and the para-compounds yield bis-diazo compounds of the type XN2•C6H4•N2X.

End of Article: AMINES

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