HILL AND CORNELISON. — CR0T0N0LACT0NE3. 19 



point (G4°), and other characters, to be tetrabromfurfuran. Hill 

 and Sanger * had previously found that this substance was formed in 

 considerable quantities when bromine was gradually added to the 

 dibrompyromucic acid suspended in water. 



Action of Oxidizing Agents. 



As we already have said, dibromcrotonolactone may be crystallized 

 without alteration from concentrated nitric acid, but on long boiling 

 it is slowly oxidized, and mucobromic acid or dibrommaleic acid 

 formed. Even fuming nitric acid attacks it with difficulty, and after 

 boiling for half an hour the greater part of the lactone taken may be 

 recovered unchanged. We dissolved the lactone in 8 times its weight 

 of concentrated nitric acid (sp. gr. 1.42), and boiled the solution for 

 three hours under a reverse condenser. The unaltered lactone was 

 then driven off with steam, and the acid solution evaporated to small 

 volume. On cooling, mucobromic acid separated in abundance, which 

 melted at 119-120°, after recrystallization from hot water. Even 

 after boiling for six hours with concentrated nitric acid the oxidation 

 was far from complete, but it was then easy to establish the formation 

 of dibrommaleic acid through the melting point (114-115°) of its 

 anhydride. On boiling the lactone with bromine water, it is slowly 

 converted into mucobromic acid. The reaction may be hastened 

 greatly by using concentrated hydrobromic acid as a solvent, and the 

 oxidation is then completed in a comparatively short time. The 

 mucobromic acid which we obtained, when recrystallized from water, 

 melted at 120-121°. With chromic acid the action is also very slow, 

 and we have been unable to identify any products of the oxidation 

 except carbonic dioxide. If an amount of chromic acid was used 

 which corresponded to one atom of oxygen for each molecule of the 

 lactone, several hours at 100° were needed for the complete reduction 

 of the chromic acid. On distillation large quantities of the unaltered 

 lactone were obtained (melting point 90-91°), and the retort residue, 

 when evaporated to small volume, deposited nothing on cooling. This 

 residue was therefore extracted with ether, the ethereal extract shaken 

 with a dilute solution of sodic carbonate, and this alkaline solution 

 immediately acidified with hydrochloric acid, and again extracted with 

 ether. The ether then left upon evaporation a small syrupy residue, 

 which was strongly acid to test paper. After standing for several 

 days, several minute clusters of rhombic plates could be seen under 



* These Proceedings, XXI. 172. 



