144 II. CHEMISTRY OF FATTY ACIDS AND GLYCEROL 



eum lubricants,"^ and for this reason they have been added to mineral oils 

 to be used as penetrating oils"^; mixed with phosphorus pentasulfide or 

 sulfur monochloride, they may serve as extreme pressure lubricants."^ 

 The Cio to Ci8 members apparently have some use as insect repellents, ^^^ 

 while the lower members are useful as flotation agents with some of the 

 metallic ores.^" Strangely enough the nitriles are largely non-toxic, in 

 contrast to the cyanides, which have a markedl}^ poisonous activity. 



(g) Acid Halides. The halides of the fatty acids and the parent acids 

 are closely related compounds; not only can they be readily formed from 

 the fatty acids, but they quickly revert to them when exposed to water. 

 The chlorides are best known, and some bromides have also been prepared, 

 but the iodides and fluorides are practically unknown. The acid halides 

 occur only as synthetic products; because of their great reactivity, they 

 are widely used for the synthesis of products related to the fatty acids. 



a'. Methods of Preparation of Acid Halides: The principal method of 

 preparation of the acid chlorides is by the action of chlorinating agents on 

 the fatty acid or the sodium soaps. The reaction may proceed in the 

 presence or absence of solvents. The most widely employed compounds 

 for chlorination are phosphorus pentachloride (PCI5), phosphorus tri- 

 chloride (PCI3), thionyl chloride (SOCI2), silicon tetrachloride (SiCU), and 

 related compounds. Phosphorus pentachloride was the first reagent to be 

 used, and an exhaustive study was made by Krafft and Burger, ^" as early 

 as 1884, on the mechanism of its action. Many acid chlorides, including 

 lauroyl, myristoyl, palmitoyl, and stearoyl chlorides, and later undecenoyl, 

 oleoyl, and elaidoyl chlorides,"^ have been satisfactorily prepared by the 

 use of PCI5. Phosphorus trichloride has the advantage that after giving 

 up its chlorine atoms it is converted to phosphorous acid, which separates 

 as an insoluble residue from the newly synthesized acid chlorides. Taufel 

 and Kiinkele"* found that this chlorinating agent is well adapted for the 

 preparation of oleoyl chloride from its acids. 



Thionyl chloride is a useful reagent, since the end products formed from 

 the chlorination reaction are both gaseous and thus can be readily removed. 

 A theoretical yield of caproyl chloride"^ and an 82% yield of oleoyl chlo- 



651 A. W. Ralston, W. O. Pool, and J. Harwood, U. S. Patent No. 2,053,045 (Sept. 1, 

 1936). 



«2 A. W. Ralston, W. 0. Pool, and J. Harwood, U. S. Patent No. 2,053,046 (Sept. 1, 

 1936). 



663 A. W. Ralston, U. S. Patents Nos. 2,116,472 and 2,125,853 (May 3, Aug. 2, 1938). 



ss-* A. W. Ralston and J. P. Barrett, Oil & Soap, 18, 89-91 (1941). 



665 J. Harwood and W. O. Pool, U. S. Patent No. 2,166,093 (July 11, 1939). 



666 F. Krafft and J. Burger, Ber., 17, 1378-1380 (1884). 



667 F. Krafft and F. Tritschler, Ber., 33, 3580-3585 (1900). 



668 K. Taufel and F. Kiinkele, Fettchem. Umschau, 4'^, 27-29 (1935); Chem. AbsL, 29, 

 3307 (1935). 



669 D. Bardan, Bull. soc. chhn. [5], 1, 141-146 (1934). 



