C 21 Carboxyalkylation of chitosan in the gel state / Yu. A. Skorik, A. V. Pestov, M. I. Kodess, Yu. G. Yatluk // Carbohydrate Polymers. - 2012. - Vol. 90, № 2. - С. 1176-1181 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): CHITOSAN -- CHEMICAL MODIFICATION -- GEL TECHNIQUE Аннотация: This study presents a new approach for direct carboxyalkylation of chitosan in the gel state by using aza-Michael addition and substitution reactions. Various reagents were applied including acrylic and crotonic acids, and alpha-, beta-, gamma-, delta-, and epsilon-halocarboxylic acids. The reaction of chitosan with gamma- and delta-halocarboxylic acids showed no target product formation either in solution or in the gel state. In the case of acrylic, crotonic, alpha- and beta-halocarboxylic acids, the reaction performed in the gel state (concentration of chitosan 20-40%) shows higher degree of substitution at lower reaction time and temperature than in diluted solutions (concentration of chitosan 0.5-2%). The results were discussed in terms of kinetics of the target and side reactions. H-1 and C-13 NMR confirmed that in all cases the carboxyalkylation of chitosan proceeds exclusively at the amino groups \\\\Expert2\\nbo\\Carbohydrate Polymers\\2012, v. 90, p.1176.pdf |