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We report on the direct assessment of the degree of substitution (DS) of carboxymethyl cellulose (CMC) by High Resolution Magic Angle Spinning (HR-MAS) C NMR spectroscopy. The method is applied to industrial CMCs with low and high viscosity and nominal DS, purified and technical samples, and from cellulose linters or wood. The preparation of a set of purified CMC working standards with accurate DS values for the method validation is also described. The DS values determined via HR-MASC NMR on the industrial samples are critically compared to the corresponding values achieved through the USP 37 〈281〉 method (ASH method) and the HPLC method, and the advantages and limitations of the HR-MAS NMR method highlighted. Finally, the HR-MAS NMR approach allowed the accurate DS assessment in CMC with low DS, characterized by a non-negligible fraction of non-functionalized cellulose. The proposed "effective DS" accounts for the DS of the solvent-exposed CMC.

is described. The method is based on the chromatographic separation of diastereo:meric adducts, formed as intermediates in the Homer-Wittig reaction of an all-trans undecatetraenal with a chiral phosphine oxide.A synthesis of the Eand 2-isomers of optically pure (S)-fecapentaene-12