PURDIE'S REACTION 193 



applicable to the simple hexoses. Glucose dissolved in methyl 

 alcohol and treated with silver oxide and methyl iodide yields 

 an acid syrup which undergoes decomposition when subjected 

 to distillation (Purdie and Irvine (19) ). The only product of 

 the change which can be identified is methyl oxalate, evidently 

 formed by the disruptive oxidation of the sugar molecule. 

 In order to prepare etheric derivatives of aldoses and 

 ketoses, it was found necessary to first mask the aldehydic 

 or ketonic group of the sugar by conversion into methyl 

 glucosides. 



The first of what was to prove a long and important series 

 of communications on the sugar group was made by Purdie 

 and Irvine in 1902 (19 and 22). Starting with a-methyl- 

 glucoside and submitting this, in methyl alcoholic solution, 

 to the action of silver oxide and methyl iodide, trimethyl 

 a-methylglucoside was obtained as a syrup, and was purified 

 by vacuum distillation. The substance was readily hydrolised 

 by dilute aqueous hydrochloric acid, whereby only the 

 glucosidic methyl group was removed and the corresponding 

 sugar, trimethyl glucose, thus obtained. This sugar proved 

 to be a viscous syrup which did not lend itself to further 

 work. Trimethyl a-methylglucoside was, however, found 

 to be soluble in methyl iodide, and, on treating this solution 

 with silver oxide, the remaining hydroxyl group underwent 

 methylation and tetramethyl a-methylglucoside was formed. 

 This substance was a mobile, colourless liquid, readily purified 

 by vacuum distillation. The product of its hydrolysis with 

 aqueous hydrochloric acid was found to be the crystalline 

 sugar tetramethyl glucose, a body which afterwards played 

 an important role in the chemistry of alkylated sugars. 

 Finally, when tetramethyl glucose was itself subjected to 

 alkylation, no oxidation occurred, but there resulted a mixture 

 containing tetramethyl a-methylglucoside and a large excess 

 of a crystalline isomeric substance. This crystalline substance 

 was later proved to be, not a pentamethylated aldehydic 



2B 



