ANTIGENS AS BIOCATALYSTS 



19 



H 



CeHs— C C . 



I I 



O— H H 



c. Enolization in Dilute Acid. 



H 



\ 



H 



I 

 CHa 



R— C = 0— H < > R— C— O— H 



1^ j LIBRAF 



jL^K^ MASS. 



7i^ — ' 



I 



R— C— OH + HA 

 II 

 CHa 



The enol may change to the ketone and since it has a symmetrical 

 ion as an intermediate this must lead to the racemization of the ketone 

 in case the a-carbon is asymmetric. 



In base accelerated reactions of such ketones, satisfactory explana- 

 tion of the course of the reaction involves the reversible formation of a 

 very reactive carbanion as follows: 



R— C = + A~ . > 



I 

 CH3 



R— C = -<— > R— C— 01 



I li 



CH2 CH2 



+ HA 



d. Acid-Base Catalysis of Condensation Reactions. Base Cataly- 

 sis of Condensation Reactions. 



CH3— C— CH3 + CHsCHjO" — > CH3CH2OH + CH3— C— GHz" 



II II 



o o 



Acetone Ethoxyl ion Ethyl Alcohol Anion of acetone 



O 



II 

 CH2— C— CIT3 



CH3C— CH2~ + CH3— C+— O— CH2CH3 — > CH3— C— O— CH2CH3 



U II I 



O 01 ~ iQl- 



Ethyl acetate 



