148 II. CHEMISTRY OF FATTY ACIDS AND GLYCEROL 



yield when glucose in pyridine and palmitoyl chloride in chloroform^^^ are 

 mixed at — 10°C. Many other similar derivatives have been prepared by 

 this reaction, including the sugar, hendecastearoyl raffinose, into which 11 

 acyl molecules have been introduced. 



(2) Reactions of Fatly Acids Not Related to Carboxyl Group 



There are a number of reactions on the part of the fatty acids and their 

 triglycerides which are referable to the aliphatic chain and not to the 

 carboxyl group. Acids which possess unsaturated linkages or a reactive 

 group such as the hydroxyl radical on the side chain readily undergo numer- 

 ous changes. The principal reactions of interest to the fat chemist are hy- 

 drogenation, halogenation, and oxidation. 



a. Hydrogenation. The reactions of hydrogen with organic compounds 

 are of varied patterns. On the one hand, hydrogen may add to unsatu- 

 rated linkages, thereby causing a partial or a complete saturation of the 

 product. On the other hand, this element may bring about reduction, as 

 for example that of a fatty acid to the corresponding alcohol. The latter 

 process is often referred to as hydrogenolysis to distinguish it from the more 

 frequent addition reaction known as hydrogenation. The present discus- 

 sion is concerned only with the latter type of reaction. 



A number of methods of hydrogenation have long been available. These 

 include those procedures in which hydrogen is generated by water or acid 

 with sodium, zinc, or other metals, or by the use of hydrazine or such re- 

 ducing agents as hydriodic acid. All of these changes involve the produc- 

 tion of so-called "nascent" hydrogen, which is able to react in a manner 

 impossible for molecular hydrogen. 



The advent of catalytic hydrogenation as a result of the classical experi- 

 ments of Sabatier and Senderens,^^""^^^ which have been summarized in 

 the monograph of Sabatier, ^^^ has made possible the extensive application 

 of this technic not only to fatty acids and more especially their triglycerides, 

 but also to a large number of related products. Although Goldschmiedt^^^ 

 had demonstrated the conversion of oleic to stearic acid previous to this 

 time, by treatment of the unsaturated acid with fuming hydriodic acid 

 and phosphorus, no widespread commercial application of hydrogenation 



"9 K. Hess and E. Messmer, Ber., B54, 499-523 (1921). 



58" P. Sabatier and J. B. Senderens, Co7npt. rend., 128, 1173-1176 (1899). 



581 P. Sabatier and J. B. Senderens, Compt. rend., ISO, 1761-1764 (1900). 



582 P. Sabatier and J. B. Senderens, Cmnpt. rend., 132, 210-212, 566-568, 1254-1257 

 (1902). 



683 P. Sabatier and J. B. Senderens, Compt. rend., 134, 1127-1130 (1902). 



58^ P. Sabatier and J. B. Senderens, Compt. rend., 135, 87-89 (1902). 



58* P. Sabatier, Catalysis in Organic Chemistn/, translated bj^ E. E. Reid, Van Nos- 

 trand, New York, 1923. 



586 G. Goldschmiedt, Sitzber. Akad. Wiss. Wien, Math, naturw. Klasse, Abt. II, 72, 

 366-375 (1875). 



