26 II. CHEMISTRY OF FATTY ACIDS AND GLYCEROL 



prepared a 6-octadecynoic acid (petroselinolic acid) by the action of 

 potassium hydroxide on 6,7-dibromostearic acid, which was obtained by 

 the bromination of petrosehnic acid. Although 9-stearohc acid (known 

 simply as stearolic acid) has only been prepared synthetically by debromina- 

 tion of 9,10-dibromostearic acid,^' it has long been known as a representa- 

 tive of this group. Another triple-bonded acid, behenolic, CH3(CH2)7Ci- 

 C(CH2)uC00H, has been synthesized from erucic and brassidic acids, 

 which are the cis and trans forms, respectively, of the monoethynoid C22 

 acid. 



b. 6,9-Octadecenynoic Acid. A second naturally occurring triple- 

 bonded acid which also contains a double bond has been isolated from the 

 nut-bearing plant Ongokea klaineana {Onguekoa Gore Engler) by Steger and 

 Van Loon^- in 1937. The positions of the double and triple bonds are not 

 known with certaint}^, but the acid may be C-octadecen-9-ynoic or 9-octa- 

 decen-6-ynoic acid. 



c. Isamic Acid. Steger and Van Loon^^ have also reported a second 

 ethynoic acid in Ongokea oil which possesses two acetylenic and one 

 ethylenic bond. Castille^^ confirmed this finding and named it erythro- 

 genic acid. Steger and Van Loon^^ presented evidence that the structure 

 Avas CH2:CH(CH2)4CiCC:C(CH2)7COOH, which is one of the two struc- 

 tures suggested by Castille. These workers called the compound isamic 

 acid. 



(6) Hydroxy- and Keio- Acids 



Although such compounds as |S-hydroxybutyric acid (CH3CHOHCH2- 

 C-OOH) and acetoacetic (or diacetic) acid (CH3COCH2COOH) are well- 

 known decomposition products of the fatty acids, the occurrence of such 

 partially oxidized fatty acids as components of the natural fats is quite 

 limited. The profound importance of such products in the animal is indi- 

 cated by their presence in such structural lipids as the cerebrosides. The 

 presence of the hydroxyl group confers some special properties upon such 

 acids. Solubility in water is increased when sufficient hydroxyl groups are 

 incorporated in the molecule, while their solubility in ether (especially 

 petroleum ether) and to some extent in alcohol is depressed by the in- 

 troduction of large numbers of hydroxy groups into the molecule. More- 

 over, they can be dehydrated to form unsaturated acids. In the case of 

 castor oil, which contains a large proportion of the ester of ricinoleic acid 

 (CH3(CH2)5CHOHCH2CH:CH(CH2)7COOH), conjugated or non-con- 



91 O. Overbeck, Ann., l.',0, 39-75 (1866). 



92 A. Stegei- and J. Van Loon, Ft'tte u. Seifrn, 44, 243-246 (1937); Chem. AbsL, 32, 

 4366 (1938). 



93 A. Castille, Ann., 543, 104-110 (1940). 



9* A. Steger and J. Van Loon, Rec. trav. chim., 59, 1156-1164 (1940). 



