118 II. CHEMISTRY OF FATTY ACIDS AND GLYCEROL 



As early as 1906, lialler^^^ demonstrated that the methyl esters of fatty 

 acids and glycerol are formed when the fats are heated with an excess of 

 methanol to which 1-2% of hydrochloric acid has been added. The low 

 molecular weight triglycerides such as are present in coconut oil^"" react 

 most readily, since they are more soluble in alcohol than the longer chain 

 triglycerides ; castor oil is easily reactive because ricinoleic acid dissolves in 

 alcohol.^"' Although h3^drochloric acid is generally used as a catalyst, 

 phenylsulfonic acid is also satisfactory.'*"^ The reaction proceeds when 

 alkali hydroxides are used as catalysts,^"* or when the reaction is carried 

 out under pressure. ^"^ In the case of ethanolysis, the ester interchange has 

 been shown to be a stepwise reaction, since it has been demonstrated that 

 di- and monoglj^cerides are intermediate products.'*"^ Thus, from the 

 partial alcoholysis of 3000 g. of tristearin in the presence of hydrochloric 

 acid, Griin et al.^'^^ were able to separate 400 g. of unchanged triglyceride, 

 300 g. of distearin, 200 g. of monostearin, and 1200 g. of ethyl stearate. 

 This process is closely related to interesterification, which is described more 

 thoroughly in Chapter III. 



c'. Reaction of Alkyl Halides (or Dialkyl Sulfates) with the Acids or 

 Their Salts: Typical reactions are given below: 



These reactions are classical methods for the preparation of all of the esters. 

 They have also been used to establish the structure of the esters. 



d'. Reaction of Acid Halides and Alcohol: The acid chlorides readily 

 react with alcohols to form esters according to the following reaction : 



.0 ,0 



RC-CI + HOCH2R ^RC-OCHjR + HCI 



Acid Alcohol Ester 



chloride 



398 A. Haller, Compt. rend., US, 657-661 (1906). 

 «« G. D. Elsdon, Analyst, 38, 8-11 (1913). 

 ^»i A. Haller, Compt. rend., lU, 462-466 (1907). 

 «2 A. Haller and Youssoufian, Compt. rend., I4S, 803-806 (1906). 

 ^«3 Y. Toyama and T. Tsuchiya, /. Soc. Chem. Ind. Japan, 36, suppl., 232-233B (1933). 

 «< V. L. Hansley, U. S. Patent No. 2,177,407 (Oct. 24, 1939). 



«sA. Griin, F. Wittka, and E. Kunze, Chem. Umschau, 24, 15-16, 31-34 (1917); 

 Chem. Abst., 13, 2768 (1919). 



