THE ALKALOIDS 355 



Cocaine. C 17 H 21 O 4 N. 



Cocaine is found in the leaves of coca, Erythroxylon Coca, from 

 which it is prepared as follows : 



The leaves are treated with hot water at a temperature of about 80. The 

 filtered solution is precipitated with lead acetate to remove tannins, proteins, 

 etc. The excess of lead is removed from the filtrate by adding sodium 

 sulphate, and the solution, after again filtering, is made alkaline with soda 

 and extracted with ether. The residue obtained on evaporation of the ether 

 is crystallised from alcohol. 



Properties. 



Cocaine separates out in colourless prisms which melt at 98. It is 

 not easily soluble in water, but is soluble in organic solvents. It is a 

 strong base forming salts, the hydrochloride being the salt most fre- 

 quently used in medicine. Its use in medicine depends upon its being 

 a local anaesthetic. 



Constitution. 



On hydrolysis by acids cocaine is converted into methyl alcohol, 

 benzoic acid and ecgonine. 



Ecgonine has been found to be closely related to tropine and is a 

 carboxylic acid of tropine : 



CH 3 



Cocaine is the double ester of ecgonine with benzoic acid and 

 methyl alcohol and has the following constitution : 



CH-COOCH 3 



This formula has been proved by the synthesis of cocaine from 

 these constituents. 



Other esters of ecgonine have been prepared using different acids in 

 the place of benzoic acid and different alcohols in the place of methyl 

 alcohol. 



