366 Mr Fenton, Oxidation in Presence of Iron. 



is effected at a low temperature and the intermediate compound 

 subsequently decomposed by heating. 



Ruff [Ber. 1898. 1573 et seq.] has since applied this method 

 with much success to several other processes of similar degradation 

 in the case of monobasic acids and brings about the operation in 

 a single stage. He modifies the method by using a ferric salt 

 instead of a ferrous salt, and operates at a higher temperature at 

 starting, without isolation of an intermediate product. In this 

 way, for example, he obtains d. arabinose from gluconic acid, and 

 d. tetrose from d. arabonic acid. 



Oxidation of Polyhydric Alcohols. 



[Fenton and Jackson, Trans. Ghent. Soc. 1899. 1.] 



The influence of ferrous iron in assisting and regulating oxida- 

 tion is again illustrated to a marked degree in the case of poly- 

 hydric alcohols. These substances when treated with hydrogen 

 dioxide alone are either unaffected or very slowly and incompletely 

 oxidized, but in presence of a small quantity of ferrous iron a 

 vigorous oxidation immediately ensues with considerable evolu- 

 tion of heat. In this manner glycollic aldehyde is formed from 

 glycol, glyceraldehyde from glycerol, tetrose from erythritol and 

 mannose from mannitol. Hexoses are also obtained from dulcitol 

 and sorbitol. This method probably affords the simplest and 

 most direct method of oxidizing the polyhydric alcohols. Mono- 

 hydric alcohols of the C m H 2W+1 OII series appear to be unaffected. 



In the cases of glycol, glycerol, and erythritol the oxidations 

 may, as in the case of tartaric acid, be effected by atmospheric 

 oxygen in presence of iron when exposed to sunlight. 



Oxidation of Acids. 



[Fenton and Jones, Trans. Chem. Soc. 1900. 69. Fenton, B. A. 

 Report, 1899.] 



As in the case of tartaric acid and the polyhydric alcohols the 

 presence of ferrous iron is found to exert a similar remarkable 

 influence in the oxidation of all hydroxy-acids, in addition to 

 many cyclic and unsaturated acids. Owing to the selective 

 character of this oxidation-process it is possible in many cases to 

 obtain products which cannot be directly prepared in any other 

 way. Some of the more important results obtained may be 

 briefly summarised as follows — 



Saturated aliphatic acids which do not contain hydroxyl or 



