Structural Characterization of 6-Halo-6-Deoxycelluloses by Direct-Dissolution Solution-State NMR Spectroscopy.

Regioselective modifications of cellulose using activated cellulose derivatives such as 6-halo-6-deoxycelluloses provide a convenient approach for developing sustainable products with properties tailored to specific applications. However, maintaining precise regiochemical control of substituent distribution in 6-halo-6-deoxycelluloses is challenging due to their insolubility in most common solvents and the resulting difficulties in precise structure elucidation by modern instrumental analytical techniques. Herein, we present an accessible NMR-based approach toward detailed characterization of 6-halo-6-deoxycelluloses, including the determination of the degrees of substitution at carbon 6 (DS 6 ). We show that the direct-dissolution cellulose solvent, tetrabutylphosphonium acetate:DMSO-d 6 , converts 6-halo-6-deoxycelluloses to 6-monoacetylcellulose, enabling in situ solution-state NMR measurements. We employ a range of one- and two-dimensional NMR experiments to demonstrate the quantitivity of the conversion and provide optimum dissolution conditions. In comparison with other NMR-based derivatization protocols for elucidating the structure of 6-halo-6-deoxycelluloses, the presented approach offers major advantages in terms of accuracy, speed and simplicity of analysis, and minimal requirements for reagents or NMR instrumentation. This article is protected by copyright. All rights reserved.