THE CHEMISTRY OF COFFEE 169 



The decomposition products of caffeine include methylhydantoin. 



CH3 



/ 



CH2 N 



^O 



CO NH 



Comparison shows that the caffeine molecule and also the uric acid 

 molecule are formed by the union of two nitrogenous rings. The 

 one found in dimethylalloxan is a hexatomic ring and the one in 

 methylhydantoin is a pentatomic ring. Thus there are two possible 

 atomic groupings for caffeine; namely, 



c , c 



/\ CH3 /\ 



/ \ / / \ 



CH3 N C N CH3 N C N 



I i /^ I I /^ 



C C N C C N 



\ / or \ / \ 



N N 



I I 



CH3 CH3 



Fischer has shown that the first form is correct, as it alone possesses 

 the atomic grouping which contains the chain of dimethylamide, 

 CH3-NH-CO-CO-NH-CH3, which is another decomposition prod- 

 uct obtained by him. This being the case, the position of the double 

 bond, of the two oxygen atoms, and of the hydrogen atom was solved 

 by Fischer from his research on oxycaffeine and hydroxycaffeine. 



Caffeine reacts with halogens to form substitution products in 

 which the substituted halogen atom readily exchanges for other 

 radicles. Caffeine also forms unstable addition products with bro- 

 mine. Chlorcaffeine, C8H9CIN4O2, is converted into methoxy- 

 caffeine, C8H9N402(OCH3), when treated with caustic soda in 

 methyl alcohol. Methoxycaffeine, boiled with dilute hydrochloric 

 acid, eliminates methyl chloride; and oxycaffeine, C8H10N4O3, is 

 formed. 



