196 A GENERAL REVIEW OF 



carbon atom. The view prevails that the interchange of 

 positions of the radicles cannot occur directly, but is due to 

 rupture of the oxidic ring, and it has been suggested that the 

 rupture is accompanied by union of the molecule with a 

 molecule of water. The fact that tetramethyl glucose shows 

 marked mutarotation in such solvents as benzene and carbon 

 tetrachloride from which all traces of water have been care- 

 fully removed, at once disposes of all theories of the mechanism 

 of the isodynamic change, which assume the addition of water 

 or of alcohol to the molecule of the sugar (Purdie and Irvine 

 (25) ). Tetramethyl glucose can be obtained in two forms, 

 the a- and )8-isomerides, and these are similar, in their nature 

 and mutarotation, to the corresponding varieties of glucose 

 itself. Tetramethyl a-glucose, when dissolved in water, 

 alcohol, benzene, toluene, or carbon tetrachloride, has initially 

 a high dextro-rotation falling until a constant value is reached ; 

 the /3-isomeride shows a low dextro-rotation initially, and this 

 rises to the same equilibrium value. The values for the 

 initial and equilibrium rotations are little affected by the 

 nature of the solvent, a fact which seems to point to the 

 elimination of the constitutive effect of the hydroxyl groups 

 by methylation. This study of the alkylated glucoses and 

 glucosides was continued by the correlation of the tetramethyl 

 a-glucose with tetramethyl a-methylglucoside and of the 

 /3-sugar with the corresponding glucoside. Irvine and 

 Cameron (28) completed the identification of tetramethyl 

 /3-methylglucoside by preparing it by direct alkylation 

 of ^8-methylglucoside. The ^-glucosides can therefore be 

 alkylated by means of the silver oxide reaction in the same 

 manner as their a-isomerides. The production of tetramethyl 

 /3-methylglucoside by alkylation of tetramethyl glucose in the 

 usual manner has already been mentioned. Curiously enough, 

 this alkylation proceeds at -10 C., and takes exactly the same 

 course as when carried out at higher temperatures (Irvine 

 and Moodie (36) ). Further experiments by the same authors 



