CHOLINE AND ALLIED SUBSTANCES 57 



/Br 

 (CH 3 ) 3 : N + Br . CH 2 . CH 3 . Br = (CH 3 ) 3 : N( 



\CH 2 .CH 2 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 3 ) 3 : N( + AgN0 8 + H,O = (CH 3 ) 3 1 N/ + AgBr + HNO 3 



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



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

 hours (Kriiger and Bergell [1903]) 



/Br /Br 



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



\CH 2 . CH 2 Br X CH 2 . CH 2 OH 



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

 into ethylene chlorohydrin cooled to - 12 to - 20 in a tube which 

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

 (Renshaw [1910]). 



/Cl 



(CH 3 ) 3 i N + Cl . CH 2 . CHoOH = (CH 3 ) 3 N/ 



\CH 2 . CH 2 OH. 



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

 under amino-ethyl-alcohol]) 



/I 



3(CH 3 )I + 2NaOH + NH,CH 2 . CH a OH = (CH 3 ) 3 1 N/ + 2NaI + 2H 2 O. 



\CH 2 . CH 2 OH 



The methods of Kriiger 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 Stanek utilises potassium tri-iodide. The two last named 

 methods are more or less quantitative. Stanek '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). 



