HILL AND CORNELISON. — CROTONOLACTONES. 11 



could hardly be explained except by assuming that the aldehyde group 

 was itself first attacked, and the lactone then formed by the elimination 

 of hydrobromic acid from the body 



B ^ - cgfe 



BrC - COBr 



This explanation seemed to us exceedingly improbable, and we fur- 

 thermore showed by direct experiment that no perceptible amount of 

 the dibromcrotonolactone could be formed by the action of stannous 

 chloride and hydrochloric acid upon mucobromic acid itself, or by its 

 reduction with zinc and acetic acid, while the alcohol acid 



Br {[ - C OH 

 BrC - COOH 



which would be formed if the aldehyde group were readily reduced 

 would certainly yield the lactone with facility. The ready formation 

 of mucobromylbromide by the action of bromine at 100° upon the 

 dibromcrotonolactone seemed equally conclusive, and the lactone 

 formula for mucobromylbromide established. Since phosphorous tri- 

 bromide converts mucobromic acid almost quantitatively into its brom- 

 anhydride, the lactone structure of mucobromic acid itself seemed to be 

 proved. It can hardly be supposed that a bromide of the lactone 

 formula could be formed from the aldehyde acid, for this would im- 

 ply the replacement of the aldehyde oxygen through the phosphorous 

 tribromide leaving the hydroxyl of the carboxyl group to form the 

 lactone by the elimination of hydrobromic acid. Although Hill and 

 O. R. Jackson * showed many years ago that mucobromic acid could 

 readily be converted into dibrommaleic acid by means of argentic 

 oxide, it was evident that even this mode of oxidation no longer war- 

 ranted a definite conclusion as to its aldehyde character. We there- 

 fore thought it necessary to take up the study of the behavior of 

 mucobromic and mucochloric acids, as well as the related acids con- 

 taining the phenoxy group, toward hydroxylamine. We found that 

 these four acids gave oximes with ease, and in studying more in detail 

 the compounds formed from mucobromic acid we found that they were 

 perfectly analogous to the bodies formed by the action of hydroxyl- 

 amine upon opianic, phthalaldehydic, and pseudopianic acids as 



* These Proceedings, XVI. 186. 



