132 II. CHEMISTRY OF FATTY ACIDS AND GLYCEROL 



^0 /OH 



C- 



RC-H + HCN »R-C-CN 



Alk\l 

 cjiinohydrin 



The cyanohydrins are soluble in most organic solvents such as diethyl 

 ether, ethanol, benzene, petroleum ether, and chloroform. Their chief 

 utility lies in the fact that they can be hydrolyzed to give a hydroxy-acid 

 having one more carbon atom than the original aldehyde. They have been 

 widely used in the synthesis of the carbohydrates. When the hydrolysis is 

 only partial, the cyanohydrins yield a-hydroxy-amides. With ammonia, 

 the aldehydes yield a-hydroxylamines. 



Of the many other condensation reactions, that with the alcohols is 

 probably best knowni. These condensation products are known as acetals ; 

 they are more readily formed by the longer chain aldehydes than by those 

 having a smaller number of carbon atoms. The formation of acetals is 

 catalyzed by acids; however, this is an equilibrium reaction, since the ace- 

 tals are hydrolyzed to the aldehyde and the alcohols when boiled with 

 mineral acids. A typical reaction of ethyl alcohol and octanal is given 

 below : 



CH3(CH2)6C-H + 2CH3CH20H^=^CH3(CH2)6C(qj,j^^^^+H20 

 Octanal Ethanol Octanal diethyl acetal 



Hemiacetals are formed when equimolecular mixtures of aldehydes and 

 alcohols react. ^" A typical preparation of such a compound from 1- 

 heptanol and heptanol is as follows: 



/i /OH 



CHj(CH2)5C-H+CH3(CH2)5CHjOH-^CH3(CHj)5C-OCH2{CH2)5CH3 



~^H 



Heptanal 1 -Heptanol Heptanal-hemi- 



heptanol acetal 



(6) Alcohols. The higher alcohols are found as components of the waxes, 

 in which they are combined with the fatty acids. In addition to the large 

 number of alcohols which can be considered to be derived from the saturated 

 aliphatic fatty acids, there are those which correspond to the common 

 unsaturated acids. Oleyl alcohol is one of the representatives of this 

 group; it has a wide natural distribution. The sterols are a third group of 

 alcohols of major importance biologically. However, since all of these 

 alcohols are present in the so-called non-saponifiable residue, a discussion 

 of them is included in Chapter IV. 



"^ Anonymous, Ann. Rept, Essential Oils, Synthetic Perfumes &c., Schimmel & Co., 

 71-74 (1933); Chem. Abst., SO, 3774-3775 (1936). 



I 



