356 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Cinchonine. C 19 Hjj 2 ON 2 . 



Cinchonine is present together with quinine in the varieties of cin- 

 chona bark, the grey bark containing as much as 2-5 per cent. 



It is prepared from the solutions remaining from the preparation of quinine ; 

 they are made alkaline with caustic soda and the precipitate so formed is 

 dissolved in a small quantity of boiling alcohol; on cooling, cinchonine is 

 deposited. It is purified by converting it into its sulphate and crystallising 

 from water. 



Cinchonine separates in colourless prisms which melt at 255, is soluble 

 with difficulty in water, but more easily soluble in alcohol, ether, etc. It is a 

 weak base and it forms salts with acids. It is a tertiary base, combining with 

 two molecules of methyl iodide. 



Constitution. 



Cinchonine is an unsaturated compound and combines with two atoms of 

 bromine, or with one molecule of hydrochloric acid. 



On oxidation it yields cinchonic acid or quinoline-y-carboxylic acid and 

 another product which has been shown to be a piperidine derivative. 



Cinchonine is thus a derivative of quinoline and contains a piperidine 

 ring. Its constitution is the following : 



H 



OH H 



17 



Quinine. C 20 H 24 N 2 O 2 . 



Quinine, together with cinchonine, is contained in cinchona bark 

 up to about 3 per cent, ; the yellow bark of Calisaya contains up to 

 1 2 per cent. 



Preparation. 



The bark is powdered and treated with dilute sulphuric acid ; from the acid 

 solution the bases are precipitated by adding soda. The mixture of bases is 

 dissolved in alcohol and the solution is neutralised with sulphuric acid. The 

 sulphates, which are so obtained, are recrystallised from water. Quinine sul- 

 phate is the most insoluble and separates out first. It is converted into 

 quinine by precipitation with ammonia. 



Properties. 



Quinine crystallises from water with three molecules of water of crystallisa- 

 tion. The anhydrous substance melts at 173. It is very slightly soluble in 

 water, but is soluble in alcohol and ether. It has a bitter taste and is a feeble 

 base. It forms salts with acids. The sulphate and hydrochloride are used in 

 medicine. Like cinchonine it is a ditertiary base and combines with two mole- 

 cules of methyl iodide. 



Quinine may be tested for by the following reaction : 



A solution of a quinine salt on the addition of chlorine water or bromine 

 water followed by ammonia gives a green precipitate. This dissolves in ex- 

 cess of ammonia giving an emerald-green solution. 



