Infrared Absorption Spectra in the Study of Mutarotational Equilibria of Monosaccharides

The infrared absorption spectra (in the range of 5000 to 250 cm(−1)) of 6 anomeric pairs of sugars and of 12 single anomers are presented, together with the spectra (in the range of 5000 to 667 cm(−1)) of the dry lyophilizates of the respective equilibrium solutions of these 18 sugars in water. Analysis of the spectra indicated the presence, in a number (possibly, in all) of the equilibrium mixtures, of some of the carbonyl form (aldehydo or keto) of the respective sugar. Conclusions as to the other components of each equilibrium mixture agreed with those derived from mutarotational studies, except for d-lyxose and d-ribose. Despite the reported absence of mutarotation for d-gluco-heptulose and d-manno-heptulose, the equilibrium mixture of each was found to contain one or more forms different from that originally dissolved.