168 PREPARATION OF METHYLATED SUGARS 



Again, in view of their convenient solubilities and the 

 tendency of partially methylated sugars to display suspended 

 mutarotation, it is evident that these compounds are suit- 

 able substances for the study of the rotatory powers of a- 

 and y8-forms and of the rotatory changes shown in the forma- 

 tion of equilibrium mixtures, as it is possible to obtain an 

 accurate polarimetric record of the tautomeric changes without 

 calculation of the true initial values. In this way we have 

 shown that both monomethyl and dimethyl glucose conform 

 to the generalisation established recently by C. S. Hudson 

 regarding rotatory power in the sugar group. The general 

 question of the optical effect of methylation on the rotatory 

 powers of glucose has also been studied in the course of the 

 work. The results will shortly be published, but the discus- 

 sion is beyond the scope of this paper. 



With regard to the application of the new compounds in 

 testing the theories of alcoholic fermentation it is evident that 

 the use of monomethyl glucose offers special advantages. 

 The current theories are chiefly based on the analogy of other 

 reactions of sugars, and can thus be tested by the isolation of 

 the intermediate products of the change. Although research 

 in this direction has been highly profitable, the results obtained 

 are in many cases conflicting or even contradictory. It will, 

 however, be seen that, using monomethyl glucose as a sub- 

 strate, the destiny of the methyl group at once gives a clue 

 to the mechanism of alcoholic fermentation, as the position 

 of the alkyloxy group in the molecule is known. Thus, 

 according to Baeyer's dehydration theory, the fermentation 

 products should be (1) methyl alcohol, (2) ethyl alcohol, 

 (3) lactic acid, and (4) carbon dioxide. Wohl's theory, on the 

 other hand, admits of a greater number of possibilities, but the 

 most feasible should result in the formation of 7i-propyl alcohol, 

 ethyl alcohol, a-hydroxybutyric acid, and carbon dioxide. 



Similarly the dimethyl glucose now described should give 

 either (1) dimethyl ether and ethyl alcohol, or (2) methyl 



