Structure of Simpler Organic Compounds.: 1-pl 



R-COv 



R-CO/ 



These can be prepared by treating an alkali salt of the 

 acid with its acid chloride, for example 



CHg-COOK + CH 3 COC1 = KCl + CH 3 -CO CO CH 3 

 When the alkali salt is treated with phosphorus oxy- 

 chloride, the salt yields acetyl chloride, which then reacts 

 with more salt. This is the more general method of pre- 

 paration, the formation of the anhydride being represented 

 by the equation 



4CH 3 -COONa + POC1 3 = 2(CH 3 CO) 2 + NaP0 3 + SNaCl 



The anhydrides, like the acid chlorides, readily react with 



substances containing a hydroxyl group ; thus, with water 



(CH 3 -CO) 2 + H 2 = 2CH 3 -CO-OH 



the anhydride being reconverted into its acid. With 

 alcohol 



(CH 3 CO) 2 + C 2 H 5 OH = CH 3 -COOC 2 H 5 + CH 3 CO OH 



In this case a mixture of acid and ester is obtained. 



Acetic anhydride, (CH 3 CO) 2 0, is a liquid with irritant, 

 unpleasant odour, of boiling point 137. 



(c) AMIDES. 



When an ester, an anhydride, or acid chloride of an 

 acid is treated with ammonia a product is obtained which 

 may be regarded as derived from a carboxylic acid by the 

 replacement of its hydroxyl group by another group con- 

 taining the elements NH 2 , and known as the amido 

 group. 



These reactions, in the case of the acetic acid deriva^ 

 tives, may be represented by the equations 



CH 3 COOC 2 H 5 + NH 3 = CH 3 CO NH 2 + C 2 H 5 OH 

 (CH 3 CO) 2 + 2NH 3 = CH 3 CO NH 2 + CH 3 CO ONH 4 



