1 70 GLUCOSIDES 



whilst the enzyme amygdalase,* contained in yeast, is only 

 able to effect a partial hydrolysis to glucose and mandelo- 

 nitrile glucoside.f 



C^H^NO,! + H 2 = C 6 H 12 O 6 + C :4 H 17 NO 6 



On the other hand, emulsin can hydrolyse other gluco- 

 sides, besides amygdalin, such as salicin, arbutin, etc. 



THE CONSTITUTION OF THE GLUCOSIDES. 



The constitution of the natural glucosides can be best 

 understood by a brief consideration of the simplest known 

 artificial glucosides which have been synthesized from glucose. 



The constitution of glucose is ordinarily represented by 

 the formula CH 2 OH CHOH CHOH CHOH CHOH CHO, 

 which shows it to be a pentahydric alcohol and an aldehyde 

 at the same time. When dissolved in water, however, it 

 behaves in a peculiar manner, exhibiting the phenomenon 

 of muta-rotation, that is to say, the optical activity of the 

 resulting solution does not attain a steady value until some 

 time after the solution has been made up. 



The change is supposed to be connected with some altera- 

 tion in its molecular configuration which may be explained by 

 assuming that the compound 



/OH 

 CH 2 OH CHOH CHOH CHOH CHOH CH/ 



is temporarily formed, J but that water is thereupon split off 

 again between one of the hydroxyl groups of the terminal 

 carbon atom and the hydroxyl attached to the fourth carbon 

 atom as follows : 



OH 



/OH 



\OH 



CH a OH CHOH CH CHOH CHOH CH 



CHjOH CHOH CH CHOH CHOH CHOH + H,O 



*Caldwell and Courtauld: " Proc. Roy. Soc., Lond.," B., 1907, 79, 350. 



t Fischer: " Ber. deut. chem. Gesells. ," 1899, 28, 1509. 



Compare the formation of similar compounds from other aldehydes (p. 149). 



