FT-IR and FT-raman spectroscopy study of the cyclic anhydride intermediates for the esterification of cellulose: III. Cyclic anhydrides formed by the isomers of cyclohexanedicarboxylic acid |
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Authors: | Charles Q Yang Guobao Zhang |
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Institution: | (1) Department of Textiles, Merchandising and Interiors, The University of Georgia, Athens, GA 30602, USA |
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Abstract: | Multifunctional carboxylic acids have been used as crosslinking agents for cotton and wood pulp cellulose. In our previous
research, we found that a polycarboxylic acid esterifies cellulose through the formation of a 5-membered cyclic anhydride
intermediate by the dehydration of two carboxyl groups. In this research, we studied the formation of cyclic anhydride intermediates
by different isomers of cyclohexanedicarboxylic acid (CHA) so that we can elucidate the effects of molecular structure on
the formation of the anhydride intermediates. We found that both cis-and trans-1,2-CHA form 5-membered anhydride intermediates
when temperature reaches their melting points and that cis-1,2-CHA forms the cyclic anhydride at temperatures lower than does
trans-1,2-CHA. 1,3-CHA forms 6-membered cyclic anhydride at temperatures much higher than its melting point. The formation
of a 5-membered cyclic anhydride intermediates takes place at temperatures lower than that of a 6-membered anhydride. This
is probably the main reason why those polycarboxylic acids with their carboxylic acid groups bonded to the adjacent carbons
of the molecular backbones are more effective crosslinking agents for cellulose than those with their carboxylic groups bonded
to the alternative carbons. No formation of cyclic anhydride was found for 1,4-CHA. The formation of a five-membered cyclic
anhydride was accelerated by monosodium phosphate, which is used as a catalyst for the esterification of cotton cellulose
by polycarboxylic acids. |
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