THE AMINO ACIDS 141 



CH 2 . NH 2 . HC1 

 COOC a H 6 . 



The ester is obtained by evaporating off the alcohol, making alkaline 

 with soda and extracting the ester with ether. The esters of amir.o 

 acids are generally oily liquids having an alkaline reaction. They can 

 be distilled in vacua. The complex mixture of amino acids which 

 results on the hydrolysis of proteins is separated by fractional distil- 

 lation of the esters in vacuo. 



B. As Amine. 



(1) Glycine forms salts with acids, e.g. : 



CH 2 .NH 2 .HC1 

 COOH. 



These salts are generally crystalline and very easily soluble in water 

 and are acid in reaction. 



Glutamic acid hydrochloride is soluble with difficulty m concentrated 

 hydrochloric acid and is separated from a mixture of amino acids in 

 this way. 



The amino acid is obtained from the salt by neutralising with soda, 

 or other alkali, e.g. silver hydroxide, and crystallisation. 



(2) Ammonia is not evolved on boiling an amino acid with sodium 

 hydroxide (compare acid amides). 



On boiling a solution of glycine with caustic soda, no evolution 

 of ammonia can be detected by smell, litmus paper, etc. 



(3) Like amines, amino acids are decomposed by nitrous acid. On 

 adding dilute hydrochloric acid and a few drops of sodium nitrite 

 solution to a solution of glycine, there is an evolution of nitrogen : 



CH 2 .NH 2 CH 2 .OH 



+ HN0 2 = | + N 2 +H 2 0. 



COOH COOH 



The corresponding hydroxy acid is formed. 



(4) On treating with acid chlorides, the amino acids yield substi- 

 tuted amides : 



CH. . N H 2 CH 2 . NH . OC . CH. 



+ CH 3 COC1= | 

 COOH COOH 



CHo . NH 2 CH 2 . NH . OC . C 6 H B 



+ C 6 H 6 COC1 = | 

 COOH COOH 



Benzoyl glycine 



or 

 hippuric aead. 



The benzoyl derivatives are readily formed by shaking the amino 

 acid in solution in sodium bicarbonate with benzoyl chloride. 



