577 



establishment of the internal equilibrium between two stereo-isomeric 

 forms. ' 



Constitution of the mono-hydrates in the sugar series. 



Tollens was the first who ascribed a lacton structure to the «- 

 and i^J-modifications of the sugar series. 



For glucQse we should e.g. have the two following contigurations : 



CH,OH . CHOH . CH . CHOH . CHOH . C<^j^and 



I — I 



CH,OH . CHOH . CH . CHOH . CHOH . C<^^ 



I 1 



which, therefore, only differ hy the asymmetry of the final carbon 

 atom. These compounds contain, therefore, no aldehyde group, and 

 it is in accordance with this that they do not colour fuchsine sulphuric 

 acid, form no bi-sulphite compounds, and do not exhibit any tendency 

 to polymerisation. 



Simon, aud especially Armstrong have succeeded in showing the 

 probability of this structure, the latter by demonstrating that the 

 two methylglucosides « and /?, which certainly do not contain an 

 aldehyde group, are converted to « and ^ glucose by hydrolysis 

 with enzymes. 



Hudson ^) advanced facts in 1909, which gave a very great probability 

 to this formula. 



He says namely this-, if we assume that the «- and ^-modifications 

 of the aldoses possess the structure proposed by Tollens, the molecular 

 rotation of one may be represented by the sum -{- A -{- B (^ = 

 rotation of the asymmetric tinal carbon atom, Z? := rotation of the 

 rest of the molecule) and of the other by — A -\- B (rotation of the 

 group B diminished by that of the levo-rotatory tinal carbon atom). 



The difference between the molecular rotations of the «- and /?- 

 modifications is therefore 1A and the sum 2B. From this it follows 

 that all the aldoses not substituted at the final carbon atom will 

 have to exhibit a constant difference of 2^, whereas the same aldoses 

 with different groups at the final carbon atom must all yield the 

 same values of 2B. 



Hudson found this prediction actually confirmed, not only for the 



^) The signification of certain numerical relations in the sugar group. J. Amer. 

 Ghem. See. 81 66. 



