102 OXONIUM COMPOUNDS MCIXTOSH 



has 59.0 per cent. Methyl acetate-bromine. This sub- 

 stance was found to contain 77.3, 78.7 per cent, bromine; one 

 with three bromine atoms requires 76.4 per cent. 



Normal propyl acetate. The compound melted at — 38**, 

 and contained 67.7, 66.4 per cent, halogen. The tribrom acetate 

 requires 70.2 per cent. 



The chlorine addition product was made, but its melting 

 point was so low that it M^as not analysed. 



Isoamyl acetate. The chlorine compound contained 

 45.2, 43.1 per cent. For three atoms of chlorine 45.0 is re- 

 quired. The corresponding bromine substance could not be 

 made. 



It will be noticed that the difficulty in making the oxonium 

 compound increases with the complexity of the organic compo- 

 nent. Perhaps the mobility of the hydrogen atom is largely 

 responsible for the existence of compounds such as HBr ^Hfi, 

 etc. 



Substitution takes place quickly in acetoacetic ether even 

 at a very low temperature. Knorr'^has shown that in this ester 

 the enol and keto forms are in equilibrium. Possibly compounds 

 could be made from the keto isomeridc. 



Acetic anhydride. The 94 per cent, material was separated 

 from acetic acid by cooling to a low temperature, and then 

 fractionated repeatedly, the part distilling between 139° and 

 140» being retained. This had a density of 1.0753 at 20°/4° 

 and froze at -72". Walten and Withrow''' give a freezing-point 

 of -86° to this anhydride. 



Apparently compounds were formed witli both halogens. 

 They were analysed, and the complete freezing point curves 

 determined. But neither method fixed their exact composi- 

 tions; for the maxima on the curves showed compounds con- 

 taining three halogen atoms, while the analyses indicated only 

 two. This point will be examined later. 



13. B. B. 44,1138 (1911). 



14. Jour. Am. Chem. Soc. 45,2690. (1923V 



