PURDIE'S REACTION 201 



Now it has been shown that methylglucoside and sucrose yield 

 methylated derivatives when alkylated, and these two 

 methylated substances yield the same tetramethyl glucose 

 upon hydrolysis. It follows, therefore, that the constitution 

 and linkage of the glucose group in sucrose must be the same 

 as in the simple glucoside. In view of the experimental 

 evidence, obtained in this work, bearing on the constitution 

 of methylglucoside, it will be seen that the above formula is 

 verified so far as it represents the glucose half of the molecule. 

 The only other disaccharide which has been alkylated 

 by the silver oxide method is maltose. The sugar, in methyl 

 alcoholic solution, was twice subjected to the action of silver 

 oxide and methyl iodide, and the product being now soluble 

 in methyl iodide, received two further treatments without the 

 addition of alcohol. Methylation was here accompanied by 

 oxidation of the free aldehydic group and subsequent esteri- 

 fication of the resultant carboxyl group. The viscid product 

 was hydrolysed by dilute hydrochloric acid, and eventually 

 yielded a syrup from which, after distillation in a vacuum, 

 crystalline tetramethyl glucose was isolated. Evidence as 

 to the mode of linkage of the glucose residues in maltose has 

 been lacking, but was furnished by these experiments. Fischer 

 suggested that such linkage might be either of an acetal or of 

 a glucosidic type. In the latter case the molecule of maltose= 

 may be represented thus : 



CHO . (CHOH) 4 . CH 2 . . CH . (CHOH) 2 . CH . CHOH . CH 2 OH 



Q 



(or by the corresponding y-oxidic formula). Whether the link- 

 age be of the acetal or of the glucosidic nature, the glucose 

 residue containing the free aldehydic group would undergo 

 oxidation during alkylation. The remaining half of the 

 maltose molecule would yield a pentamethyl glucose on 

 hydrolysis of the alkylation product if the linkage were of the 

 acetal form. But such is not the case ; maltose cannot 



2c 



