10 CHEMICAL STATICS 



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

 tended to form glycocoll anhydride: 



(In the absence of water) 

 NH 2 .CH 2 .COOH + C 2 H 5 OH = NH 2 .CH 2 .COOC 2 H5 + H 2 0. 



(Glycocoll) (Ethyl glycocollate) 



(In the presence of water) 

 NH 2 .CH 2 .COOC 2 H 5 + NH 2 .CH 2 COOC 2 H 5 = 



(Ethyl glycocollate) (Ethyl glycocollate) 



/CH 2 -NH. 



O = C, X C = + 2C 2 H 5 OH. 



N NH.CH 2 / 



(Glycocoll 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 possibility 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 : 



, CH 2 .NH x CH 2 .NH 2 .HC1 



NH.CH 2 NH.CH 2 .COOH 



(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 HC1, the ethyl ester of 

 glycyl-glycin is obtained: 



/CH2.NH, .CH 2 NH 2 



NH.CH 2 NH.CH 2 .COOC 2 H 5 



(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 NH 2 group, and the consequent 

 difficulty of obtaining simple anhydrides renders this procedure 



