PROTON MAGNETIC RESONANCE SPECTRA OF D-GLUCOPYRANOSE POLYMERS

Abstract

The proton magnetic resonance spectra of carbohydrates in deuterium oxide solution were obtained and considered with respect to probable conformation. The anomeric proton signal occurred at lowest field and was easily recognized. In the various glucose derivatives investigated, this signal occurred from 4.62 to 5.25 τ for equatorial protons and from 5.12 to 5.65 τ for axial protons. Within each of these ranges, the chemical shifts varied inversely with the electronegativity at the C1 site, as calculated by the technique of Gordy (1). Variable electronegativity at C1 accounts for the overlap of ranges for equatorial and axial protons, thereby bringing the n.m.r. data into agreement with assignment of the C1 chair form of the pyranose ring to the linear polymers of D-glucopyranose. The orientation of the glucopyranose rings in cyclodextrins is shown to preclude ring current effects, and the up-field chemical shifts of these materials are shown to be consistent with the C1 form.