38 PROCEEDINGS OF THE AMERICAN ACADEMY. 



was removed by distillation, the residue transferred to a weighing 

 tube and heated to 60-80° in vacuo. The liquid residue which 

 remained weighed 0.13 grm., and on cooling to 13° it almost com- 

 pletely solidified. The well pressed crystalline solid remained friable 

 at the temperature of the room (20°) and melted at 25-26°. Ee- 

 crystallization from a mixture of ether and ligroiu failed to raise this 

 melting point. It was thus proved that the /3-chlorcrotonolactone had 

 been formed by the decomposition of the /38-dichlorpyroruucic acid. 



a-CHLORCROTONOLACTONE. 



The a-chlorcrotonolactone melting at 52-53° was prepared several 

 years ago by Hill and L. L. Jackson * through the decomposition of 

 the yS(x)-dichlorpyromucic acid. The close relationship between this 

 substance and a body of similar composition containing bromine, 

 which had been discovered by Hill and Sanger,f was recognized at 

 the time, but no attempt was made to establish experimentally this 

 connection. The body containing bromine, which was described by 

 Hill and Sanger, has already been shown to be the a-bromcrotono- 

 lactone, and it is easy to establish the identity in structure of the 

 bromine and chlorine derivatives through the reaction with aniline. 

 The a-chlorcrotonolactone when dissolved in dilute alcohol yields with 

 aniline the a-phenylamidocrotonolactone melting at 217-218°, which 

 we have already described as prepared in the same way from the 

 a-bromcrotonolactone. 



Since the a-bromcrotonolactone had been made from the /3S-dibrom- 

 pyromucic acid through the reduction of the brommaleylbromide, 

 which is formed from it by the action of bromine, it seemed to us of 

 interest to prepare the a-chlorcrotonolactone by the same method 

 from the /38-dichlorpyromucic acid. Pure /38-dichlorpyromucic acid 

 was suspended in 25 times its weight of cold water, and dissolved by 

 the cautious addition of sodic carbonate. Two molecules of bromine 

 were then added to the feebly alkaline solution, and the whole al- 

 lowed to stand over night. As the oil which had separated would 

 not crystallize when strongly cooled and scratched, it was taken up 

 with ether, and the residue left on the evaporation of the ether dis- 

 solved in 80 per cent acetic acid. Zinc dust was then added to this 

 solution with careful cooling. When the reaction appeared to be 

 complete, the filtered solution was diluted, extracted with ether, the 

 ethereal solution washed with sodic carbonate and distilled. The 



* These Proceedings, XXIV. 353. t Ibid., XXI. 158. 



