BROMINE WATER IN SYNTHETIC ORGANIC CHEMISTRY. 559 



hydrin were 40'8 and 59*2, respectively. This yield of 

 ethylene bromohydrin is equal to the highest recorded as 

 obtainable by the action of a carefully prepared solution of 

 hypobromous acid upon ethylene. 



In view of the laborious and unsatisfactory methods used 

 in the preparation of aqueous solutions of hypochlorous and 

 hypobromous acids and the consequent difficulty of obtain- 

 ing halogenohydrins directly from unsaturated substances, 

 it was considered of importance to ascertain whether the 

 readily accessible reagent bromine water could be utilised 

 as a source 'of hypobromous acid in other reactions of a 

 similar type. 



The second substance to be selected for investigation in 

 this connection was cinnamic acid. The result in this case 

 was even more striking than with ethylene. We have been 

 able to demonstrate that under suitable conditions cinnamic 

 acid reacts speedily and quantitatively with bromine water, 

 giving a yield of over 80 per cent, of the bromohydrin, i.e., 

 /3-phenyl-a-bromohydracrylic acid (commonly known as 

 phenyl-a-bromolactic acid). The other product of the reac- 

 tion is cinnamic acid dibromide: — 



(1) 6 H 5 OH:OHOOOH + HO Br = 



OeHsOHOHOHBrOOOH; 



(2) 6 H 5 OH:OHOOOH + Br 2 = 



6 H 5 OHBrOHBrOOOH. 



In order to obtain the maximum yield of the bromohydrin, 

 the cinnamic acid is subjected to vigorous mechanical 

 stirring in contact with about thirty times its weight of 

 ice-cold water, into which a slow current of air charged 

 with bromine vapour is introduced through a perforated 

 glass bulb. 



Under these conditions absorption of the bromine takes 

 place rapidly at first, but slackens gradually towards the 

 end of the reaction. A very slight excess over the calcu- 



