CHEMICAL PROPERTIES OF FATTY ACIDS AND RELATED COMPOUNDS 131 



A similar reaction which the aldehydes undergo is a condensation with 

 ketones to form hydroxy-ketones. 



The oxidation reactions are a second important group. The end prod- 

 uct in most cases is the fatty acid, irrespective of whether a stiong acid 

 Hke chromic^®^ or peracetic acid^^^ is employed or a slow oxidation by air 

 takes place. In the latter case, an intermediate production of a peroxide is 

 believed to occur. The heavy metals such as silver and iron act as excel- 

 lent catalysts. The high yield of acids when the liquid aldehydes are 

 treated with copper salts is the basis of a Canadian patent.^" Potassium 

 permanganate is a powerful oxidant, since it can completely oxidize the al- 

 dehydes not only of the monobas'ic but also of the dibasic acids. ^^^ 

 Nitric acid is also an excellent oxidizing agent, but some nitrogen com- 

 pounds are formed in addition to the fatty acids. ^^^ The action of silver 

 oxide, or better ammoniacal silver nitrate, as an oxidation reagent on alde- 

 hydes*®^ is so delicate that it may be employed to detect minute amounts of 

 the latter compounds. 



The third group of reactions of the aldehydes can be classified as reduc- 

 tion reactions. When aldehydes are treated with reducing agents such as 

 zinc-hydrochloric acid or sodium-amalgam-ethanol, the corresponding 

 alcohols are produced.*®^ Reichstein el al^^^ have proposed the use of 

 aluminum or aluminum isopropoxide for the reduction of unsaturated alde- 

 hydes to the corresponding unsaturated alcohols. In addition to the simple 

 reduction of the aldehyde to the corresponding alcohol, other compounds 

 may originate under special types of treatment. For example, when pres- 

 sure hydrogenation is employed in the presence of a nickel catalyst on dec- 

 anal, a secondary alcohol with 20 carbons can be isolated.*^" 



Many other reactions of the aldehydes can be considered as additive 

 reactions. In these changes, the double-bonded oxygen on the terminal 

 carbon is usually combined with hydrogen, which permits the addition of 

 another atom or group to the terminal carbon atom. The sulfite derivate 

 formed when aldehydes are treated with sodium bisulfite is an example of 

 this type of reaction. The cyanhydrin reaction is another additive reaction 

 of wide importance in synthetic organic chemistry. Hydrogen cyanide 

 reacts with the higher aldehj^des to form aldehyde cyanhydrin, according 

 to the following scheme : 



« W. H. Perkin, Jr., Ber., 16, 210-213 (1883). 



8» J. D'Ans and A. Kneip, Ber., 48, 1136-1146 (1915). 



" W. J. Toussaint, Canadian Patent No. 383,687 (Aug. 29, 1939). 



« A. Baeyer, Ber., 30, 1962-1965 (1897). 



«« G. Ponzio, J. prakt. Chem. [2], 53, 431-432 (1896). 



" M. Del^pine and P. Bonnet, Compt. rend., 149, 39-41 (1909). 



«« F. Ivrafft, Ber., 23, 2360-2364 (1890). 



«* T. Reichstein, C. Amnxann, and G. Trivelli, Helv. Chim. Acta, 15, 261-268 (1932). 



™ J. V. Braun and G. Manz, Ber., B67, 1696-1712 (1934). 



