T. Rosenau, A. Potthast, A. Hofinger, H. Sixta, P. Kosma
Hydrolytic Processes and Condensation
Reactions in the Cellulose Solvent System N,N-Dimethylacetamide/Lithium Chloride. Part 1.
Summary
Refluxing of cellulose samples in N,N-dimethylacetamide (DMAc, 1), or in DMAc containing low concentrations
of LiCl, is a common protocol to facilitate dissolution of the cellulose for GPC measurements.
The formation of chromophoric condensation products, whose structures have been elucidated
for the first time, and of secondary chromophores by reaction with carbohydrate structures has been
demonstrated.
DMAc containing traces of water is slowly hydrolyzed to dimethylammonium acetate (2) under
reflux conditions. The reaction is accelerated in the presence of lithium chloride. In contrast, absolute
DMAc produces five different condensation products upon thermal treatment, which were isolated by
non-traditional column chromatography approach. The primary condensation product N,N-dimethylacetoacetamide
(3) is formed as the major component and acts as the precursor to the other chromophore
products, namely dehydroacetic acid and isodehydroacetic acid derivatives. Compound 3 is able to form
furan derivatives by reaction with reducing end groups or carbonyls in carbohydrate structures as demonstrated
by reactions with model compounds. As a consequence, it must be concluded that heating/refluxing
in DMAc or DMAc/LiCl generates a number of potent chromophores from the solvent and, furthermore,
can chemically alter pulp samples by introducing reactive structures.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 55, 11/2001
Pages: 661 - 666
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