22 W. G. OVEREND AND M. STAGEY 



been used'^^ successfully for indicating the position of D-ribose on paper 

 chromatograms. 



Ribose may be determined by conversion into furfuraldehyde which 

 may be estimated as the phloroglucide'-"' '-' by colorimetric methods'^^' ^^^ 

 or by separation on the paper-partition chromatogram and subsequent 

 estimation by sodium metaperiodate.^-'*' '-^ Under standard conditions the 

 formation of crystalline o-ribose p-toluenesulf onylhydrazone is quantitative 

 and may be used for the determination of D-ribose.*^ Solutions of the pentose 

 (1-4%) in methanol may be determined with an accuracy of ±1 %. 



3. Properties and Derivatives 



a. Physical Properties 



Ribose (d-, l- and DL-forms) crystallizes without water of hydration. 

 Values reported by various workers for the melting point and specific 

 rotation are listed in the Appendix (Table VII) (p. 65). The refractive in- 

 dex and optical crystallographic properties of the D-isomer have been de- 

 scribed/-^ and Ellinghaus^" has reported the heat of combustion for the 

 sugar. From results of a polarographic study of D-ribose, Cantor and 

 Peniston^28 concluded that in aqueous solution 8.5 to 30 % of this sugar is 

 present in the aldehyde form. (The corresponding value for arabinose is 

 0.13 to 0.4 %.) The mutarotation of d- and L-ribose in aqueous solution at 1° 

 was studied by Isbell and his colleagues/-^ and was shown to be complex. 

 The mutarotation takes place rapidly and the direction of the change re- 

 verses after a few minutes so that the initial and final rotations are not very 

 different. On account of the rapidity w^ith which the reaction takes place, 

 the mutarotational changes are best observed at low temperatures. It was 

 concluded that in solution, equilibria probably exist involving both pyra- 

 nose and furanose forms. The initial mutarotational change of D-ribose 

 suggests that in the usual crystalline form it exists as the /3-anomer. Bred- 

 ereck et al.^^ examined the mutarotation of D-ribose (at 20°) and 5-0-trityl- 

 D-ribose (at 3°) in pyridine solution. Whereas the mutarotation of D-ribose 



"9 E. Pacsu, T. P. Mora, and P. W. Kent, Science 110, 446 (1949). 

 "0 A. W. Schorger, Ind. Eng. Chem. 15, 742 (1923). 



121 C. Dor^e, "Methods of Cellulose Chemistry," p. 381. Chapman & Hall, London, 

 1947. 



122 Sonia Dunstan and A. E. Gillam, /. Chertl. Soc. 1949, S. 140. 

 >23 G. R. Barker, J. Chem. Soc. 1950, 1636. 



124 E. L. Hirst and J. K. N. Jones, J. Chem. Soc. 1949, 1659. 



12* E. L. Hirst, L. Hough, and J. K. N. Jones, /. Chem. Soc. 1949, 928. 



i2« G. T. Keenan, J. Wash. Acad. Set. 16, 433 (1926). 



1" J. Ellinghaus, Z. physiol. Chem. 164, 308 (1927). 



128 S. M. Cantor and Q. P. Peniston, /. Am. Chem. Soc. 62, 2113 (1940). 



123 F. P. Phelps, H. S. Isbell, and W. Pigman, /. Am. Chem. Soc. 56, 747 (1934). 



