CHEMISTRY OF RIBOSE AND DEOXYRIBOSE 



23 



Table I 

 Oxidation of Ribose with Bromine 



Sugar 



Av. value 

 of velo- 

 city const. 

 X 10' 



Relative 



reaction 



rates ifsugar/ 



■'^a-D -glucose 



Ratio of 



rates for 



a- and 



/3-isomers 



Mutarotation 

 constant at 0.2° db 



0.2°C. 

 wi X 10^ mi X 10^ 



D-Ribose (crystalline) 196 6.1 



;3-D-Ribose (from equilib- 1010 32 



rated solution) 



L-Ribose (crystalline) 195 6.1 



/3-L-Ribose from equilib- 1456 45.5 



rated solution) 



5.2 



6.87 



54.0 



Table II 

 R/? Values (corrected to 20°) of d-Ribose on Whatman No. 1 Filter Paper 



Solvent" 



Additions" 



R/ 



Phenol 

 s-Collidine 



n-BuOH (40%) 

 Acetic acid (10%) 

 Water (50%) 



n-BuOH (40%) 

 Ethanol (10%) 

 Water (50%) 



n-BuOH (45%) 

 Ethanol (5%) 

 Water (49%) 



1-BuOH 



Isobutyric acid 

 Methyl ethj-l ketone 



NH3 (1% wt./vol.) HCN 

 None 



None 



NH3 (1%) 



NH3 (1% wt./vol.) 



NH3 (1% wt./vol.) 



None 



NH3 (1% wt./vol.) 



0.59 

 0.56 



0.31 

 0.285 



0.210 



0.180 

 0.220 

 0.165 



Unless otherwise stated, all percentages are on a vol./vol. basis. 



in this solvent is complex, that of the 5-trityl derivative, which cannot 

 exist in a pyranose form, is of the normal first-order type of reaction. The 

 explanation forwarded for the anomalous results with D-ribose was based on 

 furanose-pyranose interconversions. The bromine oxidation of ribose equili- 

 brated in aqueous solution has been investigated. ^^^^ '^° Initial rapid oxida- 

 tion is followed by a decrease in the reaction rate, a change ascribed to the 

 presence of a small quanity of some form which is oxidized more readily 

 than the crystalline form of the sugar. Table I illustrates the results ob- 

 tained. 



"0 H. S. Isbell and W. Pigman, J. Research Natl. Biir. Standards 18, 141 (1937). 



