Structure of Simpler Organic Compounds. 89 



times called), on boiling with dilute mineral acids, undergo 

 hydrolysis to yield acids 



R-CN + 2H 2 = R-C0 2 H + 2NH 3 



(the ammonia will, of course, combine with the acids). 



This reaction is of practically universal application, 

 and is repeatedly employed in the synthesis of acids. By 

 means of it formic acid can be obtained from hydrocyanic 

 acid (HCN), and acetic acid from acetonitrile. Now the 

 nitriles themselves are readily obtained from halogen 

 derivatives when the latter are treated with potassium 

 cyanide. Thus, methyl iodide when treated with potassium 

 cyanide reacts thus 



CH S I + KCN = CH 3 CN- + KI 

 The cyanide on hydrolysis yields acetic acid 

 CH 3 CN + 2H 2 = CH 3 C0 2 H + 2NH 3 



This synthesis indicates that in acetic acid there is a 

 methyl group. A similar conclusion can be drawn from 

 the fact that acetic acid can be derived from the oxidation 

 of ethyl alcohol (through aldehyde) 



CH 3 CH 2 OH - CH 3 -CHO CH 3 C0 2 H 



The constitution of the acids can be further exemplified 

 by certain reactions of acetic acid itself. Of the four 

 hydrogen atoms contained in the formula C 2 H 4 O 2 , one and 

 one only is replaceable by a metal. Furthermore, this 

 hydrogen atom, together with O (combined together in a 

 hydroxyl group), is replaceable by a halogen. Now when 

 acetic acid is treated with chlorine, a series of products can 

 be obtained, in which consecutively one, two, or three 

 hydrogen atoms are replaced by the halogen. It might be 

 expected, from what 'has been already learnt of the 

 formation of substitution products, that this substitution 

 should take place in the alkyl (methyl) group. If this is 



