158 II. CHEMISTRY OF FATTY ACIDS AND GLYCEROL 



This constant is of some value in indicating the complexity of molecular 

 structure. 



Potassium permanganate is probably the most widely used oxidizing 

 agent for unsaturated acids. When the reaction is carried out in an 

 aqueous alkaline medium at 0° to 30 °C., the products formed are pre- 

 dominantly polyhj^droxy-acids, which are usually geometric isomers of the 

 original acids. ^^* If an excess of alkali is avoided, the end products of the 

 oxidation of oleic acid with permanganate are 9-hydroxy-lO-ketostearic and 

 9-keto-lO-hydroxystearic acids."^-"^ On the other hand, when a non- 

 aqueous medium such as acetone is used,^" or when an acidic solution is 

 employed at an elevated temperature, fission results through the rupture of 

 the fatty acids at the double bonds. ^" 



The polyhydroxy-acids which were shown by Hazura^^^ to be produced 

 by alkaline permanganate oxidation of a number of unsaturated acids are 

 isted in Table 49. 



Table 49 



Products of Alkaline Permanganate Oxidation of Unsaturated Acids Obtained 



BY Hazura" 



" K. S. Markley, Fatty Acids, Interscience, New York, 1947, p. 394 (from K. Hazura, 

 Monatsh., 8, 260-270 (1887)). 



Hydrogen peroxide and related peroxides react with the unsaturated 

 acids. Although no reaction would be detected with oleic acid at ordinary 

 temperatures,"^ Hilditch^^" demonstrated the formation of dihydroxystearic 

 acid when oleic acid was refluxed for 8 hours with hydrogen peroxide. 

 Benzoyl peroxide, (C6H5CO)202, oxidized oleic acid to dihydroxystearic 

 acid after treatment in dry ether at 2-3 °C. for 2 days.^^^ Such per acids 



6'^ A. Saytzeff, J. prakt. Chem. [N.S.], 33, 300-318 (1886). 



675 D. Hokle and J. Marcusson, Ber., 36, 2657-2662 (1903). 



6"! G. King, /. Chem. Soc, 1936, 1788-1792. 



6" E. F. Armstrong and T. P. Hilditch, /. Soc. Chem. Ind., U, 43-47T (192.5). 



6™ K. Hazura, Monatsh., 8, 260-270 (1887). 



6'9 K. Hazura, Monatsh., 9, 469-474 (1888). 



680 T. P. Hilditch, /. Chem. Soc, 129, 1828-1836 (1926). 



681 G. V. Pigulevskli and M. A. Petrov, /. Russ. Phys. Chem. Soc, 58, 1062-1066 

 1926); Chem. Abst., 22, 943 (1928). 



