Homogeneous synthesis of cellulose p-toluenesulfonates in N,N-dimethylacetamide/LiCl solvent system

Pure cellulose p-toluenesulfonates (tosylates) with an insignificant formation of chlorodeoxy groups were prepared by reacting cellulose dissolved in a solution of N,N-dimethylacetamide and LiCl with tosylchloride (Tos-Cl) in the presence of triethylamine within 24 h at 8 degrees C. Various cellulosic starting materials with a degree of polymerization from 280 to 5100 were used. The samples obtained were characterized by means of elemental analysis, FTIR and C-13 NMR spectroscopy, and their intrinsic viscosities. The rise of the molar ratio of Tos-Cl/anhydroglucose unit (AGU) from 0.6 to 9.0 leads to an increase in the degree of substitution (DS) from 0.4 up to a maximum value of 2.3. The cellulose tosylates are readily soluble in common organic solvents like dimethyl sulfoxide (within the whole DS range) and in N,N-dimethylacetamide, N,N-dimethylformamide, acetone, tetrahydrofuran and trichloromethane depending on DS. As revealed by C-13 NMR spectroscopy a faster tosylation takes place at the O-6 atom of AGU compared with the O-2/3 atoms. This was additionally confirmed by analysis of the corresponding iododeoxy celluloses synthesized with NaI in acetylacetone. Furthermore, some important properties as stability against alkaline and heat were studied as well.