Page:Encyclopædia Britannica, Ninth Edition, v. 5.djvu/589

Rh A.MIDES.] CHEMISTRY 577 Intermediate products are sometimes formed C 6 H 4 (X0 2 ) 2 Dinitrobenzene. 3H = C 6 H 4 (XO 2 )(XH 2 ) Nitraniline. 20H, The diatnines have not been investigated with the amount of detail that has been bestowed upon the mona- mines. By the action of the iodidss of C n H 2n+1 radicles upon ethene and diethene diamines a large number of bases have been obtained, in which the ammonic hydrogen is more or less replaced by these radicles. Diamines form two classes of salts, monacid and diacid. Triaminee. The following belong to this class : Guanidine or earbotriamine ........................... K 3 CH 5 Mc-lanilme or carbodiphenyl-triamine ..... ....... . .^C^H^ Triphenyl-guankline or caibotriphenyl-triamine ..... N g C| 7 H 19 Aniline Colours. A large number of the colours ob tained from aniline are triamines, and may be conveniently referred to here. Rosaniline (magenta or fuchsine) is the base of a splendid red dye which serves as the starting point of numerous other colours. It is prepared by oxi dizing a mixture of aniline and toluidine with arsenic acid : C 6 H 7 X + 2C 7 H 9 X - 3H 2 = C 20 H ]9 N 3 (Rosaniline). Mauve is a purple dye produced by the oxidation of aniline by means of sulphuric acid and potassium dichromate. The base of this colour is mauveine (C, 6 H 24 X 4 ), and it is interesting as being the first of the aniline dyes practically employed in the arts. The numerous other dyes derived from benzene, phenol, and naphthalene cannot be discussed here. It has been recently observed by Dr Otto Witt that the peculiar properties of organic colouring substances are in most cases due to the combined presence of two groups or radicles attached to a carbon nucleus. The one which is the colour-producing group is termed the ckromophore, the other is a salt-forming group, i.e, a group which confers upon a molecule either acidity or basicity. A substance containing a chromophore does not become a colour until the salt-forming group is introduced into the molecule ; such potential colouring matters ara therefore termed chromogens. The chromophoric group exercises its influ ence more powerfully in the salts of colouring substances. The principal salt-forming groups combined with aromatic nuclei are HO and XH 2, so that most chromogens of this class give rise to two colours according as one or other of the foregoing radicles enters into their composition. Phosphines, Arsines, Stibines, and Bismuthines. These compounds are analogues of the amines, and contain the above elements in place of nitrogen. Some of the methods employed in their production are seen in the followin reactions : 2PH 4 I Phosphonitim iodide. Ethyl iodide. = 2P(C 2 H 5 )H 3 Ethyl phosphonium iodide, 3Zn(C. 2 H 5 ) 2 Zinc ethide. AsXa 3 + Sodium arsenic alloy. 2PC1 3 = 3C,HI = Efhyl iodide. 2P(C-H 5 ). H Triethyl phosphine. As(C 2 H 5 ) 3 + Triethyl arsine. 3ZnCl 3XaI The corresponding tertiary stibines and bismuthines are produced by a similar reaction. The compounds of ths presen group are possessed of great affinity for oxygen, many of them taking fire spon taneously when exposed to the air. Arsendimethyl or cacodijl, As 2 (CH 3 ) 4, is a spontaneously inflammable liquid, having a most repulsive odour, produced by the action of methyl iodide on sodium arsenic alloy, or by distilling a mixture of potassium acetate and arsenious anhydride. The analogy between these compounds and the amines is still further exemplified by the following reactions : P(G 2 H 5 ) 3 + CH 3 I = P(C 2 H 8 ) 8 (CH,)I Tiiethyl phosphine. Methyl iodide. Methyl -diethy! phosphonium iodide. 2Sb(C 2 H 5 ) 4 I + Ag,0 + OH = 2Sb(C 2 H 5 ) 4 HO + 2AgI Tetrethyl Tetrethyl stibomum stibomum iodide. hydroxide P(C 2 H 5 ),HI + KHO = P(C 2 H 5 ) 3 + KI + OH 2. Triethy! phosphonium Triethyl iodide. phosphine XIV. AMIDES. The compounds of this class are most conveniently re garded as derived from acids by the substitution of XH 2 for the HO contained in the carboxyl group. It will be thus evident that monobasic acids can yield only one amide a monamide of the form R CO(NH 2 ). Polybasic acids, on the other hand, can have their hydroxyl partially or entirely replaced by amidogen, thus yielding normal and acid amides. The latter are known as amic acids: From Dibasic Acids. ,,/CO(XH 9 ) pw /CO(XH 2 ) CO(HO) k t CO(NH 2 ) Acid amide Normal amide (Amic acid). (Diamide). From Tnbasic Acids. ( CO(XH 2 ) (CO(XH 2 ) II&quot; { CO(HO) Pt &quot; &amp;lt;^ CO(XH 2 ) (CO(HO) (CO(HO) Acid amides (Amic acids). ( CO(XH 2 ) &quot;X CO(NH 2 ) (CO(XH 2 ) Xormal amide (Tnamide). Amides are primary, secondary, or tertiary, according as one-third, two-thirds, or all the hydrogen of the ammonia is replaced by acid radicles (see p. 574). Amides are produced (1.) By distilling the normal ammonium salts of the corresponding acids : CH 3 .CO(OXH 4 ) - OH 2 = CH 3 .CO(XH.,) Ammonium acetate. Acetamide. C 2 H 4 .[CO(OXH 4 )] 2 - 20H 2 = C 2 H 4 .[CO(NH 2 )] 2 Ammonium succinate. Succinamide. (2.) Also by the action of ammonia on the acid halides : CH 3 .COC1 + 2XH 3 = CH 3 .CO(XH.,) + XH 4 C1. Acetyl chloride. Acetamide. By the further action of the acid halide upon the primary monamide secondary and tertiary monamides are produced : CH 3 .COC1 + CH 3 .CO(XH 2 ) - (CH 3 CO) 2 (XH) + HC1 Acetyl chloride. Acetamide. Diacetamide. (CH 3 .COUXH) + CH 3 .COC1 = (CH 3 CO) 3 N + HC1. Diacetamide. Acetyl chloride. Ti ia cetamide. Diacetamide is also formed by the action of dry HC1 upon acetamide and triacetamide by heating acetonitrile (methyl cyanide) with acetic anhydride. The formation of amides containing dyad radicles is exemplified by the equation C 2 H 4 (COC1) 2 + 4XH 8 = C 2 H 4 .[CO(XH 2 )] 2 + 2XH 4 C1. Succinyl chloride. Succinamide. (3.) Amides are formed by the action of ammonia on the ethereal salts of the corresponding acids : CH 3 .CO(OC 2 H 5 ) Ethyl acetate&quot;! ( CO(OC 2 H 5 ) t CO(OC 2 H 5 ) Ethyl oxalate. = CH 3 .CO(XH 2 ) + C,H 5 .HO Acetamide. Ethyl alcohol. C CO(XH 2, o - C H HO 2 H 5-ttO Oxamide. &quot; Ethyl alcohol. CO(OC 2 H 5 ) CO(OC 2 H 5 ) CO(OC S H 5 ) Ethyl citrate. ( CO(XH 2 ) = (C 3 H 4 )&quot;(HO) 1 CO(XH&quot; 2 ) + 3C 2 H 5 .HO. I CO(NH.,) Citramide. Ethyl alcohol. V- - 73