556 CONSIDERATION OF CARBON COMPOUNDS. 



In one case the organic radical is in combination with carbon ; in the other, 

 with nitrogen. These compounds are apparently esters of hydrocyanic acid, 

 but they behave quite differently from esters, as they do not yield alcohols or 

 metallic cyanides on treatment with alkalies. 



Cyanides or nitriles. These may be formed by heating together iodides 

 of hydrocarbon radicals with potassium cyanide : 



CH 8 I + KCN = CH 3 CN + KI. 



The cyanides are volatile liquids or solids. When heated with water in 

 presence of mineral acids or alkalies, they yield organic acids, thus : 



CH 3 .CN + 2H 2 = CH 3 .C0 2 H 4- NH 3 . 

 Methyl Acetic acid, 



cyanide. 



This is an important reaction, as it furnishes a simple means of introducing 

 carboxyl into compounds, thus forming organic acids. For this reason the 

 cyanides are called nitriles of the acids, just as the acid oxides are called an- 

 hydrides of the corresponding acids. Thus, methyl cyanide is called aceto- 

 nitrile, because it yields acetic acid. In fact, the ammonium salts of organic 

 acids, by abstraction of water, yield cyanides : 



CH S .CO 2 NH 4 = CH 8 .CN + 2H 2 O. 



Isocyanides or carbylamines. These compounds are distinguished by a 

 disgusting odor. They are formed by heating silver cyanide, instead of potas- 

 sium cyanide, with iodides of hydrocarbon radicals, thus : 



CH 3 I + AgCN = CH 3 NC + Agl. 



It is strange, and as yet not explained, why hydrocarbon iodides produce 

 cyanides with potassium cyanide, and isocyanides with silver cyanide. 



Isocyanides are also formed by heating together chloroform, primary amines, 

 and an alkali, as shown above in the paragraph on amines. 



The isocyanides behave differently from the cyanides when heated with 

 water and acids, thus : 



CH 3 NC + 2H 2 O = CH 3 NH 2 + HCO 2 H. 



Methyl Methyl Formic 



isocyanide. amine. acid. 



Isosulphocyanates or mustard oils. The difference in structure between 

 sulpho- and iso-sulphocyanates is expressed in the following formulas : 



R S C^N, sulphocyanate. E N=C S, isosulphocyanate. 



The organic sulphocyanides are of no importance here. The principal member 

 of the mustard oils is allyl-isosulphocyanate, C 3 H 5 NCS, one of the decomposi- 

 tion products of myronic acid. 



Treated with water and alkali, mustard oils break down, thus : 



C^NCS + 2H 2 = C 3 H 5 NH 2 + H 2 S + CO 2 . 



This reaction is similar to that which takes place in case of isocyanides. (See 

 above.) 



Myronic acid, C 10 H 19 NS. 2 10 , is found as the potassium salt, which is known 

 as sinigrin, in black mustard seed. When treated with solution of myrosin, a 



