1 34 Biological Chemistry. 



They are also formed when alkyl iodides are treated with 

 silver cyanide 



cyatr + A g cN = A g i + CA-N ; c 



They are colourless liquids with a particularly objection- 

 able odour, with somewhat higher boiling points than the 

 isomeric nitriles. Their constitution is indicated by the fact 

 that they yield on hydrolysis an amine and formic acid 



C 2 H 5 -N ; C + 2H 2 = H-COOH + C 2 H 3 -NH 2 



Contrast this, reaction with that of the isomeric 

 nitrile 



C 2 H 5 CN + 2H.O - C 2 H 5 -CO OH + NH, 



Part XV. The Benzene Derivatives. 



In 1825 Faraday isolated from oil gas a hydrocarbon, 

 benzene, to which the formula C 6 H 6 is now ascribed, 

 which subsequent investigation has shown to differ 

 markedly in its properties from a hydrocarbon which 

 should, from the formula, be expected to contain three 

 double bonds. Since Faraday's original discovery, benzene 

 has been produced on a large scale as a product of coal- 

 tar distillation, and is now known to form a nucleus from 

 which a very important and interesting series of com- 

 pounds, known as aromatic derivatives, has been derived. 

 The number of these derivatives is very large, and their 

 investigation has occupied the attention of numerous 

 chemists over several decades ; many of the benzene de- 

 rivatives, furthermore, are of great technological impor- 

 tance. It will be possible in this place to deal with only 

 a very limited number. As some of them play an im- 

 portant part in the physiology of the plant and animal, 

 it is necessary to consider in some detail certain of the 

 fundamental conceptions now generally held as to their 

 constitution and structure. 



