BROMINE WATER IN SYNTHETIC ORGANIC CHEMISTRY. 561 



The processes involved in the above reaction are sum- 

 marised in the appended scheme: — 



Br 2 + HOH ZT± HBr + HO Br 



j i 



C 6 H 5 CHBrCHBrCOOH 6 H 5 OHOHOHBrCOOH. 



From this it is apparent that the production of every 

 molecule of bromohydrin involves the formation of a mole- 

 cule of hydrogen bromide. An excess of hydrobromic acid 

 in the aqueous solution, over the amount arrived at in this 

 way, will be due to decomposition of hypobromous acid in to 

 hydrogen bromide and oxygen : — 



HO • Br = HBr + O. 

 Any wastage of bromine occurring in this way may there- 

 fore be traced by estimating the amount of hydrobromic 

 acid in the aqueous solution. 



In a carefully conducted operation, 20 grams of cinnamic 

 acid yielded 6*55 grams of cinnamic acid dibromide and 27*1 

 grams of phenyl-a-bromolactic acid, CeHsOHOHOHBr* 

 OOOH + H 2 0. It is thus evident that the relative per- 

 centage amounts of cinnamic acid converted to dibromide 

 and bromohydrin were 17*1 and 82*9, respectively. 



The amount of bromine used in this operation was 21*3 

 grams; from the data just quoted, the quantities utilised 

 in forming dibromide and bromohydrin were 3*40 and 16'49 

 grams, respectively. Consequently, the wastage of bromine 

 in the operation, due to the combined causes of decom- 

 position of hypobromous acid and possible diffusion of 

 unaltered halogen, was only 6*6 per cent. This result 

 compares favourably with that obtained with ethylene, in 

 which case the loss of bromine was 8*1 per cent. In both 

 cases, however, since a certain loss of the reaction-products 

 is unavoidable during the process of their isolation, the 

 actual wastage of bromine will be somewhat less than the 

 above figures indicate. 



J j— December 5, 1917. 



