38 II. CHEMISTRY OF FATTY ACIDS AND GLYCEROL 



studies of Power and his collaborators^^^'^" between 1904 and 1907. Even 

 then, the formulas for the cyclic acids which were proposed proved to be 

 erroneous. Their structure was not completely clarified until the work of 

 Shriner and Adams ^''^ in 1925. Chaulmoogric acid was shown to be 13-[2- 

 cyclopentenyl jtridecanoic acid, the formula of which is illustrated below: 



CH2CH2CH(CH2),2COOH 



I I 



CH==CH 



Chaulmoogric acid 



Because of the asymmetr^y of the ring carbon joined to the side chain, 

 chaulmoogric and related acids are optically active. They all possess a 

 dextrorotation. When they are reduced to dihydrochaulmoogric acid, the 

 optical activity is lost. 



Racemic chaulmooghc acid was first synthesized by Perkins and Cmz^^^ 

 by condensation of the acetoacetic ester with 11-cyanoundecanoic acid, 

 Hinegardner^"^ was the first to prepare r//-chaulmoogric acid from the 

 natural rf-isomer. However, /-chaulmoogric acid has not been isolated. 

 The conversion of hydnocarpic acid to chaulmoogric acid has been ac- 

 complished by Stanley and Adams. "^^ Hydnocarpic and chaulmoogric 

 acids can be separated from the other acids and from each other, in the acid 

 mixture obtained by extraction of saponified chaulmoogra oil, by vacuum 

 distillation. ^"^'^^^ The first fraction is largely hydnocarpic acid, while the 

 third fraction is essentially pure chaulmoogric acid. 



Hydrogenation of chaulmoogric and hydnocarpic acids to the correspond- 

 ing dihydro-compounds proceeds smoothly when platinum or palladium is 

 used as a catalyst, "'*~i^'' or with a mixed platinum-palladium oxide cat- 

 alyst. ^^^ Zinc and ethanol may also be employed to produce the dihydro- 

 compounds. However, when phosphorus and hydrogen iodide are used, 

 the reduction proceeds to the hydrocarbon, chaulmoogrene, CisHs^. Some 

 chaulmoogryl alcohol is formed with sodium and ethanol, resulting in con- 

 densation to chaulmoogryl chaulmoograte. 



i«3 F. B. Power ami F. H. Goniall, /. Chem. Soc, 85, 838-851, 851-861 (1904). 



164 F. B. Power and M. Barrowcliff, ./. Chem. Soc, 87, 884-896 (1905). M. Banow- 

 cliff and F. B. Power, ibid., 91, 557-578 (1907). M. Barrowcliff and F. B. Power, Proc. 

 Chem. Soc, 23, 70-71 (1907); Chem. Abst., 1, 1561 (1907). 



165 R. L. Shriner and R. Adams, J. Am. Chem. Soc, 47, 2727-2739 (1925). 



166 G. A. Perkins and A. O. Cruz, /. Am. Chem. Soc, 49, 1070-1077 (1927). 



167 W. S. Hinegardner, J. Am. Chem. Soc, 55, 2831-2834 (1933). 



168 W. M. Stanley and R. Adams, J. Am. Chem. Soc, 51, 1515-1518 (1929). 



169 T. Hashimoto, J. Am. Chem. Soc, 47, 2325-2333 (1925). 



1™ A. L. Dean and R. Wrenshall, U. S. Pah. Health Service Pub. Health Repts., 37, 

 No. 23, 1395-1399 (1922). 



1" R. Wrenshall and A. L. Dean, U. S. Pub. Health Service Bull., Xo. 141, 12-23 

 (1924). 



172 A. L. Dean, R. Wrenshall, and G. Fujimoto, U. S. Pub. Health Service Bull., No. 

 141, 24-27 (1924). 



