496 V. CHEMISTRY OF PHOSPHATIDES AND CEREBROSIDES 



Klenk*^^ furnished additional proof by obtaining a piu'e sample of lignoceric 

 acid from cerasine, with a melting point of 83-84°C., and by also showing 

 its identity with hydrogenated nervonic acid. 



(6) Properties. Lignoceric acid is a component not only of cerasine but 

 also of sphingomyelin. It also occurs in peanut oil, and it makes up as 

 much as 25.5% of the oil of the sandal bead-tree nut^^^ (Adenanthera 

 pavonina) . 



Lignoceric acid dissolves readily in diethyl ether, petroleum ether, warm 

 alcohol, acetone, benzene, carbon disulfide, acetic acid, chloroform, and 

 pyridine. It crystallizes from alcohol on cooling, in glistening platelets. 

 It contains no asymmetric carbon atoms and is therefore optically inactive. 

 On reduction, a hydrocarbon is formed which melts at 51°C.,^^^ while on 

 oxidation an oxy-acid melting at 94-95°C. originates. ^^^ 



Lithium lignocerate is precipitated from hot alcohol when lithium acetate 

 is added. Magnesium lignocerate is formed in the same manner w^hen 

 magnesium acetate is added and the alcohol solution is allowed to cool. 

 The silver and lead salts (m.p., 117°C.) are known. ^'^^ The methyl ester 

 (m.p., 57-58°C.) and the ethyl ester (m.p., 56°C.) have similar properties 

 when prepared from synthetic or natural sources. 



c. Nervonic Acid, (a) Siruciure. This is a normal acid, as it converts to 

 n-tetracosanic acid on hydrogenation. The methyl ester of hydrogenated 

 nervonic acid^^^ is identical with that of synthetic tetracosanic acid.^^^-*^^'*^® 

 On ozonization, pelargonic acid and a ??-dicarboxylic acid, C15H28O4, are 

 obtained. ''^^•^'^'' The structural formula of nervonic acid must therefore be 

 CH3(CH2)vCH : CH(CH2)i3COOH. 



(6) Properties. Nervonic acid is present, not only in the cerebroside 

 nervone, but also in sphingomyelin. Furthermore, the acid described by 

 Tsujimoto'*"'*''^ as selacholeic acid, which is obtained from shark liver oil, 

 is apparently nervonic acid. 



Nervonic acid is a white crystalline powder which is easily soluble in 

 diethyl ether, alcohol, and acetone. It crystallizes from alcohol when the 

 solution is cooled to a low temperature. Nervonic acid melts at 40-41 °C. 

 The iodine number is 69.3. On treatment with nitric acid, it is converted 

 to its geometric isomer, which is very difficultly soluble and melts at 59°C.^^* 



The sodium salt dissolves in hot alcohol, but it precipitates on cooling. 

 It dissolves better in cold methyl alcohol. The lead salt of lignoceric acid is 



4S8 S. M. Mudbidri, P. R. Ayyar, and H. E. Watson, J. Indian Inst. ScL, All, Pt. 14, 

 173-180(1928). 



«s E. Klenk, Z. physiol. Chem., 157, 283-290 (192()). 



«« E. Klenk, Z. physiol. Chem., 166, 287-293 (1927). 



«i M. Tsujinioto, Z. deut. 01- u. Fett-Ind., 46, 385-388 (1926); Chem. Zentr., 1928, 

 I, 1385; J. Soc. Chem. hid. Japan, 29, 67-71 (1926); Chem. Abst., 20, 2421 (1926). 



«2 M. Tsujinioto, J. Soc. Chem. Ind. Japan, 30, suppl., 868-873 (1927); Chem. Zentr., 

 1928, I, 1385; Chem. Abst., 22, 1326 (1928). 



