Interpretation of Carboxymethylation in Cellulose Pretreatment by 1H-NMR Spectroscopy

Carboxymethylation reaction in cellulose was investigated with sodium hydroxide concentration, monochloroacetic acid concentration, temperature, and reaction time as main variables. The degree of carboxymethylation in cellulose was analyzed by phenolphthalein titration, IR spectroscopy, and 1H-NMR spectroscopy methods. The NMR spectroscopic method showed more accurate DS (degree of substitution) values than other IR spectroscopy or titration methods. IR method had the advantage of quick measurement but was difficult in baseline correction. The titration method needed longer data acquisition time and higher deviation to less accuracy. Carboxymethylation in cellulose was run in SN2 reaction by sodium hydroxide and monochloroacetic acid concentration with main variables. Substitution position was analyzed by 1H-NMR spectroscopic with acid hydrolysates of carboxymethylated cellulose. Carboxymethylation in lower reaction temperatures led to more C6-hydorxyl substitution reactions in cellulose, but the C6- and C2-hydroxyl group position competed with increasing reaction temperature. KCI Citation Count: 0