322 VII. ACIDS, AMIDES, ALDEHYDES AND HYDROCARBONS 



b'. Secondary Alcohols: Several secondary alcohols have like^vise 

 been demonstrated in plant products. In contradistinction to the primary 

 alcohols, these have an odd number of carbon atoms. One secondary 

 alcohol, d-n-nonacosan-10-ol, was originally isolated by Kawamura'''^ 

 from the fruit of the maidenhair tree {Ginkgo biloha), and was called ginnol. 

 Chibnall and Piper^-^ proved that the secondary alcohol is rf-n-nonacosan- 

 lO-ol. This alcohol was likewise isolated from apple cuticle wax,'" as well 

 as from the leaves of the Ginkgo biloba.^*^ 



Sahai and ChibnalP^^ discovered another secondary alcohol, namely n- 

 nonacosan-15-ol, in the leaf wax of brussels sprouts; the presence of the 

 same alcohol was later recorded in the Swede turnip. '^^ 



c'. Ketones: The possibility that ketones may be intermediates in the 

 oxidation of fatty acids, primary alcohols, and hydrocarbons, as suggested 

 by Chibnall and Piper, '^2 is supported by the discovery that n-nonacosan- 

 15-one occurs in brussels sprouts leaf wax,'^'* as well as in cabbage. '^^ 



b. Unsaturated Hydrocarbons in Plants and Animals, (a) Squalene. 

 Squalene is a highly unsaturated hydrocarbon, with an empirical formula 

 of CsoHso. It is widely distributed in the animal and plant kingdoms. 

 Squalene was first discovered as an important component of the liver oil 

 of sharks of the Squalidae family, but it has since been found to be as 

 widely distributed in the animal kingdom. Moreover, it is now recog- 

 nized as a normal component in higher animals. 



Tsujimoto'^* first reported the presence of an unsaturated hydrocarbon 

 in the liver oil of a black shark of the genus Zameus; this was later shown 

 to be squalene."^ Squalene was found to be a component of the liver oils 

 of sixteen of thirty-six species of elasmobranch fish examined, all from 

 Japanese waters, '^^ including the basking shark (Cetorhinus maximus).'^^^-^^^ 

 Hilditch'^^ also reported the presence of squalene in the liver oils of some of 

 the family Squalidae (sharks) and also of other shark families. Heilbron 

 and co-workers'^* observed the presence of this hydrocarbon in the un- 

 developed eggs (but not in the mature eggs) of the dogfish, Etmopterus 

 spinax, which is a member of the Squalidae. This would suggest that 



1" J. Kawamura, Japan. J. Chemistry, 3, 89-92 (1928). 



i"S. Furukawa, Sci. Papers Inst. Phys. Chem. Research (Tokyo), 19, 27-38, 39-42 

 (1932). 



1" M. Tsujimoto, J. Sac. Chem. Ind. Japan, 9, 953 (1906); cited by M. Tsujimoto, 

 Ind. Eng. Chem., 8, 889-896 (1916). 



i« M. Tsujimoto, Ind. Eng. Chem., 8, 889-896 (1916). 



"« M. Tsujimoto, Ind. Eng. Chem., 12, 63-73 (1920). 



'" T. P. Hilditch, The Chemical Constitution of the Natural Fats, Wiley, New York, 

 1947. 



1*8 I. M. Heilbron, E. D. Kamm, and W. M. Owens, /. Chem. Soc, 1926, 1630-1644. 



