SYNTHESIS AND CARBOXYMETHYLATION OF ORGANO-SOLUBLE TRIFLUOROACETATES AND FORMATES OF CELLULOSE

Soluble cellulose intermediates are converted into carboxymethyl cellu lose (CMC) with a high degree of substitution (DSCMC) of up to 2.2 by removing the solubilizing ester groups in an one-step synthesis in dim ethylsulfoxide (DMSO) with suspended solid NaOH powder as a base and m onochloroacetate within 4 hours at 70 degrees C. The reaction is a pse udohomogeneous conversion, i.e., it proceeds under temporary inhomogen eity of the substrate (cellulose). As confirmed by means of HPLC analy sis, these CMCs contain a significantly higher amount of both 2,3,6-tr i-O-carboxymethylated and unsubstituted units in the polymer chain tha n those obtained in a slurry of cellulose in isopropanol/water (totall y heterogeneous conversion) at comparable DSCMC. In contrast to hetero geneously prepared samples, the CMCs show a distribution of carboxymet hyl groups within the anhydroglucose unit in the order O-6 > O-3 > O-2 as revealed by means of C-13 and H-1-NMR studies. As intermediates fo r subsequent carboxymethylation, organo-soluble cellulose trifluoroace tates (CTFA) and cellulose formates (CF) have been synthesized and stu died. The CFs were obtained by a new, convenient synthesis method cons isting of the acylation of cellulose with mixtures of formic acid and phosphorus oxychloride within 4 hours at room temperature. The CFs wit h a degree of substitution (DSCF) of 2.2 are soluble in DMSO and DMF, and they show a complete substitution of the primary OH groups as conf irmed by C-13-NMR studies and HPLC analysis after permethylation and c hain degradation. The CTFAs (DSCTFA = 1.5) prepared by acylation of ce llulose with a mixture of trifluoroacetic acid/trifluoroacetic anhydri de also show a preferred substitution of the C-6 position.