Equilibria between pyranoses and furanoses. V. The composition in solution and the 13C N.M.R. spectra of the heptoses and the heptuloses.

The 13C n.m.r. spectra of nine heptoses and of all of the heptuloses were recorded and most of the signals were assigned. From these spectra, the equilibrium compositions of the heptoses and heptuloses were determined in aqueous solution. Those of the heptoses differ, with one exception, little from those of the homomorphous hexoses but some heptuloses occur wholly in the a-pyranose form, and others are predominantly in furanose forms.