10 CHOLINE 



Ducet^^ observed that free choline can be quantitatively adsorbed on 

 silica gel whereas the combined water-soluble choline remains in the solvent. 



The isolation of choline by paper chromatography was investigated by 

 Munier and Macheboeuf.^^ These workers report that non-alkaloidal sub- 

 stances such as choline and betaine are readily separated from alkaloids 

 because their partition coefficients in various solvent systems are different. 

 Choline is detected on the paper strips by the blue color formed when the 

 chromatograms are treated with solutions containing phosphomolybdic 

 acid, acetic acid and stannous chloride. Rf values are given by these workers 

 for choline when it is chromatogrammed with various solvent mixtures 

 containing n-butanol, acetic acid, and water. 



B. PHYSICAL AND CHEMICAL PROPERTIES 



Choline, hydroxyethyltrimethylammonium hydroxide, can be obtained 

 with difficulty as a colorless crystalline mass by drying under high vacuum 

 over P205.^^' ®^ It is a strong base, decomposes ammonium salts, and has 

 a marked tendency to absorb water and carbon dioxide from the air. 

 Choline has no well-defined melting or boiling point but breaks down when 

 heated into trimethylamine and glycol. Dimethylaminoethanol and di- 

 methylvinylamine are also formed in lesser amounts by thermal decompo- 

 sition of the base.^^ Dilute water solutions of the base are stable to heat, 

 but concentrated solutions give off trimethylamine when boiled. ^^ 



Choline is soluble in water, in formaldehyde, and in absolute methyl and 

 ethyl alcohols. It is sparingly soluble in amyl alcohol, chloroform, dry 

 acetone, and wet ether. Choline is insoluble in dry ether, carbon tetra- 

 chloride, carbon sulfide, toluene, benzene, and petroleum ether. ^^' ^^ 



Edsall^^ reported the Raman spectrum for choline chloride, and the 

 ultraviolet absorption spectrum of the base is described by Castille and 

 RuppaP" and by Graubner.^^ 



C. CONSTITUTION AND SYNTHESIS 



The correct structure of choline was determined by Baeyer'^^ and by 

 Wurtz," who carried out the first syntheses, using the reaction of tri- 

 es G. Ducet, Com'pt. rend. 226, 1045 (1948). 



" R. Munier and M. Macheboeuf, Bull. soc. chim. biol. 31, 1144 (1949). 

 6s K. H. Meyer and H. Hopff, Ber. 54, 2274 (1921). 

 «6 A. Wurtz, Compt. rend. 66, 772 (1868). 



67 W. Roman, Biochem. Z. 219, 218 (1930). 



68 G. Klien and H. Linser, Biochem. Z. 250, 220 (1932). 

 63 J. T. Edsall, /. Am. Chem. Soc. 65, 1767 (1943). 



70 A. Castille and M. Ruppal, Bull acad. roy. mH. Belg. 56, 263 (1926). 



71 W. Graubner, Z. ges. exptl. Med. 63, 527 (1928). 



72 A. Baeyer, Ann. 140, 306 (1866); 142, 322 (1867). 



73 A. Wurt/, Compt. rend. 65, 1015 (1867). 



