vi RING-COMPOUNDS OF AMINO-ACIDS 211 



accomplished fact, then the previously open-chain compound is con- 

 verted into a 'ring-compound.' 1 Thus 







H 

 C-C-NH, becomes OC 



/ TT 



HO/ 



Chemically active glycocoll becomes chemically inactive glycocoll. 



While glycocoll is in this inactive state it forms a true pseudo-acid- 

 pseudo-basic compound; in other words, it cannot play the part of 

 an an-ion or that of a kat-ion till the ring-like compound is reconverted 

 into an open -chain. This change can only be brought about by 

 subjecting the pseudo-acid pseudo-basic molecule to the influence of 

 ions. If active or inactive glycocoll is brought into contact with a 

 strong acid, such as hydrochloric acid, then glycocoll-hydrochloride is 

 formed : 



O x H OH 



>C-C-NH 2 +HC1 = >C-C +NH 8 .C1, 



HO 7 H HCK H 



while with sodium hydrate it forms sodium glycocollate and water. 

 0. H O. H 



>C - C - NH 2 + NaOH - >C - C - NH 2 + H 2 O. 



HCK H NaCK H 



The proximity to or the remoteness from one another of the acid and 

 basic radicals in the amphoteric amino-acid determines the ease with 

 which an internal salt is made and is unmade. As most of the normally 

 sccurring mono-amino-acids are a-compounds (p. 21) in which the 

 basic NH 2 -group is as close to the acid COOH-group as possible. 

 t follows that the length of the primary chain does not much 

 nterfere with the internal salt -formation as long as only one NH 2 

 ^adical and one CO OH radical is present : 



CH 2 CH . CH 2 CH 2 CH 2 CH 3 



O 



Glycocoll. Leucin. 



It is different, however, when two NH 2 and one COOH groups are 

 >resent, or two COOH groups and one NH 2 , as in the case of the 

 nono-amino-di-carboxylic and di-amino-mono-carboxylic acids. From 



1 Ring- formation by fusion of two molecules is described on p. 215. There are 

 tereocliemical difficulties in the way of one-molecule rings. 



