CHOLINE AND ALLIED SUBSTANCES 57 



/Br 



(CH,), ; N + Br . CH 2 . CH 3 . Br . (CH,), : N( 



\CH,.CH,Br. 



By acting on the latter substance with silver oxide, Hofmann obtained 

 the vinyl base instead of choline. Choline is however obtainable from 

 it in two ways : 



(a) by boiling for eight days with silver nitrate (Bode [1892]) 



/Br /Br 



(CH,), ; N( + AgNO, + H 2 = (CH,), : N( + AgBr + HNO, 



\CH a .CH 3 .Br \CH 2 .CH 3 OH 



(ti) by heating with twenty-five parts of water to 160 for a few 

 hours (Kriiger and Bergell [1903]) 



/Br /Br 



(CH,), : N/ + H 2 = (CH 3 ), : N/ + HBr. 



\CH, . CH a Br X CH 2 . CH 2 OH 



3. Rather more than one equivalent of trimethylamine gas is passed 

 into ethylene chlorohydrin cooled to - 1 2 to - 20 in a tube which 

 is subsequently warmed to 80-90 ; the yield is almost quantitative 

 (Renshaw [1910]). . 



/Cl 



(CH 3 ) 3 : N + Cl . CH 2 . CH,OH = (CH 3 ) 3 N/ 



\CH 2 .CH a OH. 



4. By the methylation of amino-ethyl alcohol (Trier [1912, 2; 

 under amino-ethyl-alcohol]) 



3(CH 3 )I + zNaOH + NH,CH 2 . CH,OH = (CH 3 ) a : N<^ + 2NaI + 2H 3 O. 



\CH 2 . CH a OH 



The methods of Kruger and Bergell and of Renshaw appear to be the 

 most convenient. 



A method for the estimation of choline in animal tissues has been 

 described by Kinoshita [1910, 2]. For the isolation of choline from 

 plant extracts, Jahns [1885] has employed potassium bismuth iodide 

 (Kraut's reagent), Schulze has used phosphotungstic acid and mercuric 

 chloride and Stane'k utilises potassium tri-iodide. The two last named 

 methods are more or less quantitative. Stane'k 's method [1905, 1906, 

 I, 2] is the most convenient for the quantitative estimation of choline 

 in the presence of betaine when other bases yielding periodides are ab- 

 sent (compare Kiesel [1907]). For a description of Stanek's and 

 Schulze's methods see the appendix (Chapter VIII). The tests for, 

 and chemical properties and salts of, choline are also described in the 

 appendix (Chapter VIII). 



