Elsevier

Carbohydrate Research

Volume 84, Issue 1, 8 September 1980, Pages 1-12
Carbohydrate Research

An N.M.R. study of the interactions between cadoxen and saccharides

https://doi.org/10.1016/S0008-6215(00)85424-5Get rights and content

Abstract

Cadoxen, an aqueous solution of cadmium oxide and ethylenediamine, is an effective solvent for cellulose and is known to form complexes with simpler saccharides. The 1H-, 13C-, and 113Cd-n.m.r. spectra of d-glucose, cellobiose, methyl α-d-glucopyranoside, methyl β-d-glucopyranoside, and cellulose in cadoxen are reported. Cellulose gives a well resolved 13C spectrum in this solvent, and it is assigned by comparison with the spectra of simpler sugars. The 113Cd and 13C results are not consistent with the formation of chelate alcoholate complexes involving the 2- and 3-hydroxyl groups. This form of interaction has been suggested in the literature. It seems rather that hydrogen-bonding interactions are dominant. It is suggested that the effectiveness of cadoxen and similar cellulose solvents is a result of enhanced hydrogen-bonding arising from a combination of steric and electronic factors. The metal ion serves the dual purpose of holding two amino groups in a favorable orientation for hydrogen bonding with a pair of equatorial hydroxyl groups on the carbohydrate, and of decreasing the pKa of the amino group by withdrawing electrons.Some analogies with the binding of sugars to concanavalin A are discussed.

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