OXIDATION OF ALCOHOLS 



149 



though it cannot strictly be called a fermentation if we adhere 

 to the usual definition of fermentation as an anaerobic process. 

 The biological nature of the process was demonstrated by 

 Pasteur in 1862-4, and since then many organisms of this 

 genus have been isolated from vinegar vats, etc., and have the 

 property of oxidising alcohols to acid. Acetobacter are highly 

 aerobic and carry out three main types of oxidation: 



1. Oxidation of primary alcohols to the corresponding acids: 



CH3.CH2OH + 02= CH3.COOH + H2O. 



2. Oxidation of aldehydes and aldohexoses to the corre- 

 sponding acids: 



CHiOH 



nA—\ 





H OH 

 GLUCOSE 



CH2OH 



COOH 

 HO 



H OH 



GLUCONIC ACID 



3. Oxidation of certain secondary alcohols to the correspond- 

 ing ketones. The nature of the secondary alcohols was 

 studied in detail by Bertrand in a classical work on Acetobacter 

 xylinum. By studying a large number of secondary alcohols, 

 he showed that only those possessing a specific stereochemical 

 configuration are attacked. Using the old type of straight 

 chain formula, this specific group is 



H H 



H 



HOCHo—C — C— which is oxidised to HOCH,— C— C- 



OH OH 



OH 



and the — OH group oxidised must be in the j8-position and 

 adjacent to another — OH group. Thus an alcohol with the 

 structure 



