24 PROCEEDINGS OP THE AMERICAN ACADEMY. 



obtained substantially the same result, while prolonged heating at 200° 

 brought about decomposition. We had no better success when we 

 employed hydriodic acid saturated at 0°, although in this case decom- 

 position set in at a lower temperature. 



/?-Bromcrotonolactone. 



When /38-dibrompyromucic acid is boiled with concentrated hydro- 

 bromic acid, it is slowly decomposed, carbonic dioxide is evolved, and 

 /3-bromcrotonolactone is formed. The reaction does not run as 

 smoothly as it does with tribrompyromucic acid, and more or less car- 

 bonization ensues. When the reaction appears to be completed, the 

 dilution of the dark brown solution usually precipitates a small amount 

 of dark-colored unaltered acid, but no lactone is thus thrown down. 

 The filtered solution is then extracted with ether, the ethereal extract 

 washed with a dilute solution of sodic carbonate, and dried with calcic 

 chloride. The residue left after distilling off the ether gradually 

 solidifies on standing, and the crude product, which amounts to about 

 one quarter of the dibrompyromucic acid taken, may be recrystallized 

 from small quantities of alcohol or from ether. The same body may 

 be prepared much more conveniently by the reduction of the a/3-di- 

 bromcrotonolactone with zinc dust and acetic acid. The dibromcro- 

 tonolactone is suspended in its own weight of 80 per cent acetic 

 acid, and somewhat more than the calculated weight of zinc dust is 

 then added with careful cooling. At first the reduction proceeds rap- 

 idly with the evolution of heat, but several hours at ordinary tempera- 

 tures are necessary for its completion. When the zinc has nearly 

 disappeared the viscous solution is warmed, filtered, and the clear fil- 

 trate cautiously diluted with water. The bromlactone is thus precipi- 

 tated as an oil, which after cooling and shaking soon solidifies in the 

 form of colorless feathery crystals. The precipitated lactone amounts 

 to 45 per cent of the weight of the dibromcrotonolactone taken, and 

 somewhat more may be obtained by extracting the mother liquor 

 with ether. 



T. 0.2417 grm. substance gave 0.2609 grm.C0 2 and 0.0440 grm. H 2 0. 

 II. 0.1913 grm. substance gave 0.2214 grm. AgBr. 



Found. 



II. 



49.24 



