Oxidation of regenerated cellulose with NaClO2 catalyzed by TEMPO and NaClO under acid-neutral conditions

A new TEMPO-mediated oxidation with catalytic amounts of TEMPO and NaClO, and NaClO2 as the primary oxidant under aqueous conditions at pH 3.5-6.8 was used to prepare water-soluble beta-(1 -> 4)-linked polyglucuronic acid Na salts (cellouronic acids, CUAs) with high molecular weight in good yield. When regenerated cellulose with original degree of polymerization (DP) of 680 was oxidized by the 4-acetamide-TEMPO/NaClO/NaClO2 system at pH 5.8 and 40 degrees C for 3 days, CUA with weight average DP (DPw) of 490 was obtained quantitatively. No peaks other than six signals from beta-(1 -> 4)-linked anhydroglucuronic acid units of CUA were detected in the solution-state C-13 NMR spectra of the oxidized products. Although the oxidized product prepared under the above conditions contained about 20% unoxidized cellulose particles, the non-CUA fraction was separable from CUAs by filtration or salt precipitation. The DPw values and yields of CUAs after the filtration or salt precipitation treatment were 250380 and 45-71%, respectively. (C) 2009 Elsevier Ltd, All rights reserved.