10 CHEMICAL STATICS 



in 1883, observed that ethyl glycocollate, in watery solution, 

 tended to form glycocoll anhydride: 



(In the absence of water) 

 NH2.CH2.COOH + C2H5OH = NH2.CH2.COOC2H5 + H2O. 



(Glycocoll) (Ethyl glycocollate) 



(In the presence of water) 

 NH2.CH2.COOC2H5 + NH2.CH2COOC2H5 = 



(Ethyl glycocollate) (Ethyl glycocollate) 



/CH2-NH- 



= C^ ;C = + 2C2H50H. 



^NH.CH2 ^ 



(GlycocoU anhydride) 



Obviously, if the' closed ring representing the glycocoll anhy- 

 dride molecule could be opened up without destroying the sta- 

 bility of the molecule, a new amino-acid would be formed, one 

 degree more complex than the original amino-acid (glycocoll). 

 This possibihty occurred to Emil Fischer, and he found, in fact, 

 that if the glycocoll anhydride which is thus prepared be boiled 

 for a short time with concentrated hydrochloric acid, the fol- 

 lowing change occurs: 



/ CH2.NH . / CH2.NH2.HCI 



= C^ ^C = + HCl-t-H20 = = Cf 



^NH.CH2^ ^NH.CH2.C00H 



(Glycocoll anhydride) (Glycyl-glycin chloride) 



On now treating the glycyl-glycin chloride with silver oxide, 

 silver chloride is precipitated and free glycyl-glycin is obtained. 

 (23). If, however, the glycocoll anhydride be originally treated 

 with alcoholic instead of with watery HCl, the ethyl ester of 

 glycyl-glycin is obtained: 



/CH2.NH. /CH2NH2 



= Cf ^C = + C2H50H = = C^ 



^ NH.CH2 ^ ^ NH.CH2.COOC2H5 



(Glycocoll anhydride) (Glycyl-glycin ester) 



It would almost appear, therefore, as if we had only to repeat 

 this cycle of operations indefinitely in order to secure the most 

 complex poly-amino-acids ; but this is not so easy as it might 

 appear at first sight; the instability of amino-acids consequent 

 upon the high reactivity of the NHo group, arid the consequent 

 difficulty of obtaining simple anhydrides renders this procedure 



