ANTIGENS AS BIOCATALYSTS 



23 



Esterification 

 Detailed presentation of the esterification is given below: 



R— C— OH + HA -7 y 



II 

 O 



R— C— O— H 

 I 

 lO— H 



lOH H 



I I 



R— C— O— R 



lO— H 



+ 



+ A~ + R— O— H < > 



lO— H 



I 



+A~ . > R— C— O— R + HA 

 I 

 lO— H 



Hydrolysis 



R— C— O— R + HA -7 > 



II 

 O 



R— C— O— R 



I 

 lO— H 



R— C— O— R 

 I 

 lO— H 



+ 



+IO— H:2=> 

 I 

 H 



H 



I 

 lO— H 

 I 



R— C O— R 



I 

 lO— H 



+ A" 



lO— H H 

 I I 



R— C O— R 



I 

 lO— H 



+ 



lO— H H 



I I 



R-c g— R 



I 



lO— H 



+ 



+ A~ >-R— C = + HA + ROH 



I 

 lO— H 



2. Acid Catalysis in Non- Aqueous Solvents (Aprotic) 



Acid catalysis in non-aqueous solvents such as chlorobenzene have 

 been investigated. The rearrangement of N-bromacetanilide, the inver- 

 sion of 1-menthone and the racemization of C6H5COCH-(CH3)C6H5 

 and C6H5COCH(CH3)CH2CH3 are some of the examples. The re- 

 actions are not kinetically of integral order but are fractional. With 

 respect to the substrate the order is less than one. This can be attributed 

 to hydrogen bonding type of complex formation between substrate and 

 acid if the complex is chemically unreactive. Direct evidence has been 

 found (Bell and Caldin, 1938) for the rapid and reversible forma- 

 tion of complexes of menthone with various acids resulting in the 

 depression of optical rotation. 



