12 



THE CARBOHYDRATE ECONOMY OF CACTI. 



complex reciprocal transformations of the hexoses as discovered by Lobry 

 de Bmyn and van Ekenstein. 1 Here the sugar is not decomposed, but under 

 the influence of the alkali the structural arrangement of the sugar molecule 

 is affected in such a manner as to produce a number of substances which 

 differ from each other only in respect to the position of certain chemical 

 groups within the molecule. The nature of these most important reactions 

 has been worked out by Nef. He demonstrated that an aqueous solution 

 of either d-glucose, d-mannose, or d-levulose with 1/20 equivalent of calcium 

 hydroxide attains equilibrium when kept at 15 to 20. There is thus 

 formed, when starting with any one of the above sugars, a mixture of 



OH 



OH OH 



CH 2 OH 



CH:0, CH 2 OH- 



OH OH 



OH 



OH OH 



-CH:0 



D-glucose. 

 H H OH O 



CH a OH- 



OH OH 



-CH,OH, CH a OH 



CH 2 OH 



OH OH OH 



D-fructose. 



H O OH 



CH,OH- 



OH OH 



-CH..OH, CH,OH 



CH 2 OH 



OH OH 



OH 



and a- and /?- d-glutose. 



In a similar manner the d-galactose series yields d-galactose, d-talose, 

 d-tagatose, d-sorbose, and a- and ft- d-galtose. It is noteworthy that a mem- 

 ber of the d-glucose series is never converted into a member of the d-galactose 



1 LOBBY DE BBUTN, C. A., and W. A. VAN EKENSTEIN. Action des alcalis sur les sucres. 

 II: Transformation r6ciproque des uns dans les autres des sucres glucose, 

 fructose et mannose. Rec. des trav. chim. des Pays-Bas., 14, 203-216, 1895. 



, . Action des alcalis sur les sucres. Ill: Transformations des sucres 



sous 1'influence de 1'hydroxide de plomb. Rec. des trav. chim. des Pays-Bas., 

 15, 92-96, 1896. 



Action des alcalis sur les sucres. IV: Remarques generates. Rec. 

 des trav. chim. des Pays-Bas., 16, 257-273, 1897. 



