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

Abstract

Abstract 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 LiCI with tosylchloride (Tos‐CI) in the presence of triethylamine within 24 h at 8°C. Various cellulosic starting materials with a degree of polymerization from 280 to 5 100 were used. The samples obtained were characterized by means of elemental analysis, FTIR and 13 C NMR spectroscopy, and their intrinsic viscosities. The rise of the molar ratio of Tos‐CI/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 13 C 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.