1H and 13C chemical shift assignment of the monomers that comprise carboxymethyl cellulose

H-1 and C-13 chemical shift assignment of the anhydroglucose units (AGUs) that comprise sodium carboxymethyl cellulose (CMC) with a degree of substitution (DS) of 0.70 was performed using 2D NMR spectra obtained from COSY, TOCSY, HSQC, and HSQC-TOCSY experiments. In the 2D COSY and TOCSY spectra, there are eight correlation networks for the H1 to H6' atoms of AGU; each H-1 resonance of the eight AGUs was assigned from the changes in the intensities of the resonances with mixing times during the TOCSY experiments. The ring C-13 resonances were assigned via analysis of HSQC-TOCSY spectra and confirmed via the HSQC spectra. Comparison of the shift data enabled the assignment of the eight AGUs as two types of both 2,3,6-tri-O- and 3,6-di-O-carboxymethylated, one type each of 2,6-di-O-, 2-mono-O-, and 6-mono-O-carboxymethylated AGU, and unsubstituted AGU. The obtained shift data will also be useful for characterization of the substitution distribution of other cellulose derivatives. (C) 2013 Elsevier Ltd. All rights reserved.