Knowledge Bank

An interpretation of the CH stretching VCD in sugars has been developed in terms of electronic currents generated by the C(2)H, C(3)H and C(4)H methine stretching vibrations in adjacent intramolecularly hydrogen bonded rings. A comparison of the VCD spectra of D-mannose, D-glucose and D-glucose-2-$d1$ will be presented which illustrate the model. The cancellation of ring current contributions which result in nearly zero VCD in glucose, are prevented in D-glucose-2-$d-1$ by deuteration and in D-mannose by altering the configuration at C(2); in such a way, a large monosignate negative CH stretching VCD is observed for these two sugars. The model is also shown to be consistent with VCD spectra of additional sugars surveyed $previously1$.