HILL AND CORxNELISON. — CROTONOLACTONES. 33 



The formation of the crotonolactone through the reduction of the 

 dibromcrotonolactoiie was thus established. Since the salts of the 

 oxycrotonic acid all seemed to possess the same uninviting properties, 

 and our main end was already reached, we made no further study of 

 them. 



a/3-DlCHLORCROTONOLACTONE. 



The a/3-dichlorcrotonolactone may be prepared most easily by the 

 reduction of mucochlorylbromide. This body, which has not yet been 

 described, was readily made by the action of phosphorous tribromide 

 upon mucochloric acid. The reaction ran perfectly smoothly, and but 

 little more than one molecule of phosphorous tribromide was needed 

 for complete reaction with three molecules of mucochloric acid. After 

 heating at 100° until the liquefied product grew turbid with the separa- 

 tion of phosphorous acid, the flask was well cooled, and cold water 

 added with constant shaking. The oil which separated gradually so- 

 lidified, and the granular product which was obtained could readily be 

 collected by filtration. As in the preparation of mucobromylbromide 

 we have found it easy to obtain 88-90 per cent of the theoretical 

 yield, and the crude product was sufficiently pure for further use. An 

 analysis of a sample recrystallized from ligroin gave the required per- 

 centage of halogen. 



0.2721 grm. substance gave 0.5556 grm. AgCl + AgBr. 



Calculated for C 4 HCI 2 2 Br. Found. 



CI + Br 65.09 64.91 



Mucochlorylbromide is very readily soluble in alcohol, ether, chloro- 

 form, carbonic disulphide, or benzol ; in ligroin it is somewhat more 

 sparingly soluble. From a solution in dilute alcohol it may be ob- 

 tained by spontaneous evaporation in large transparent plates which 

 melt at 36°. In alcoholic solution it gives with dilute alkalies a 

 deep purple color, which rapidly passes into a wine-red and finally to 

 yellow. With sodic carbonate we have also frequently noticed the 

 formation of a deep green color after the wine-red. 



The reduction of the mucochlorylbromide is easily effected by means 

 of stannous chloride and hydrochloric acid. The reaction proceeds 

 slowly in the cold, but may be carried to the end at ordinary tempera- 

 tures. On warming gently it runs rapidly with the evolution of heat, 

 and in a short time, if the reaction is promoted by vigorous shaking, 

 the mucochlorylbromide completely disappears. On cooling and add- 

 ing water the dichlorlactone separates in long slender needles, while 

 vol. xxix. (n. s. xxi.) 3 



