12fi II. CHEMISTRY OF FATTY ACIDS AND GLYCEROL 



aldehyde. On ozonolysis of the olefin formed by dehydration of the second- 

 ary alcohol which results from interaction of the original aldehyde and 

 phenylmagnesium bromide, benzaldehyde and the new aldehyde are 

 formed. ^**^ Finally, a chemical reduction (as opposed to catalytic reduc- 

 tion) of the ozonides will yield aldehydes. Potassium ferrocyanide^^^ or 

 zinc-acetic acid mixture^^^ may serve for such a reaction. 



The hydroxy-acids are also useful as starting materials for the synthesis 

 of aldehydes. On treatment for 24 hours with lead tetraacetate in glacial 

 acetic acid solution, 9,10-dihydroxystearic acids gave an 85% yield of 

 nonanal.^^^ Minium (Pb304) has likewise been used for the oxidative 

 splitting of 9,10-dihydroxystearic acid to nonanal.^^" Pyrolysis of ricinoleic 

 acid (12-hydroxy-9-octadecenoic acid) results in the splitting of the acid at 

 the hydroxyl group (between C12 and Cn) to form heptanal. When the 

 a-hydroxy-acids are heated to their decomposition points, aldehydes having 

 one less carbon, and formic acid, result. An example of this is the forma- 

 tion of heptadecanal in 50-00% yield, according to the following scheme, 

 when 2-hydroxy stearic acid is heated''" first at 200°C. and then at 270°C. 



CH3(CH2),5CC-OH 3«CH3(CH2),5C-H+HC-0H 



OH 

 a-Hydroxystearic Heptadecanal Formic 

 acid acid 



Another well-known method for the synthesis of aldehydes employs the 

 Grignard reagent and ethyl orthoformate, CH(OC2H6)3. Acetals are 

 produced as intermediates, and the aldehydes result on hydrolysis of the 

 acetals. Hexanal is formed in 45-50% yield by the application of this 

 procedure, as follows: 



CH3(CH2)3CH2MgBr + HC(0C2H5)j 5.CH3(CH2)4CH(0C2H5)2 + C2H50MgBr 



Pentylmagnesium Ethyl Acetal 



bromide orthoformate 



/) 

 CH3(CH2)4CH(OC2H5)2— ^^^^^^ *CH3(CH2UC-Hi-2CH3CH2 0H 



Acetal Hexanal Ethanol 



Nitriles can be quantitatively converted to aldehydes, as first suggested 

 by Stephen. ^^^ The reaction first involves the formation of an imino 



<" F. G. Fischer, H. Dtill, and L. Ertel, Ber., B65, 1467-1472 (1932). 

 ^^2 C. Harries, German Patent No. 321,567 (June 13, 1918). 



^" Y. Kobata, /. Agr. Chem. Soc. Japan, 11, 709-714 (1935); Chem. Abst., 29, 7279 

 (1935). 



''' C.-Y. Hsing and K.-J. Chang, /. Am. Chem. Soc, 61, 3589 (1939). 

 ^« H. R. Le Sueur, J. Chem. Soc, 85, 827-838 (1904). 

 <« H. Stephen, J. Chem. Soc, 127, 1874-1877 (1925). 



