lithium-chloride and 4-toluenesulfonyl-chloride

Cellulose acylation by anhydrides (ethanoic to hexanoic) plus tosyl chloride, TsCl, or imidazole in LiCl/N,N-dimethylacetamide solution has been studied. Contrary to a previous claim, TsCl does not catalyze acylation. For the diazole-catalyzed reaction, N-acylimidazole is the acylating agent. Third order rate constants (k(3); 40-70 °C) have been calculated from conductivity data and split, by using information from model compounds, into contributions from the primary- (k(3;Prim(OH))) and secondary- (k(3;Sec(OH))) hydroxyl groups of cellulose. Values of k(3,Prim(OH))/k(3,Sec(OH)) are >1, and increase linearly as a function of increasing the number of carbon atoms of the acyl group. Rate constants and the degree of biopolymer substitution decrease on going from ethanoic- to butanoic-, then increase for pentanoic- and hexanoic anhydride, due to enthalpy/entropy compensation. Relative to the uncatalyzed reaction, the diazole-mediated one is associated with smaller enthalpy- and larger entropy of activation, due to difference of the acylating agent.

Topics: Acetamides; Acylation; Anhydrides; Catalysis; Cellulose; Entropy; Imidazoles; Kinetics; Lithium Chloride; Tosyl Compounds

The tosylation of cellulose in ionic liquids (ILs) was studied. Due to the beneficial effect of different co-solvents, the reaction could be performed at 25°C without the need of heating (in order to reduce viscosity) or cooling (in order to prevent side reactions). The effects of reaction parameters, such as time, molar ratio, and type of base, on the degree of substitution (DS) with tosyl- and chloro-deoxy groups as well as on the molecular weight were evaluated. Products with a DStosyl≤1.14 and DSCl≤0.16 were obtained and characterized by means of NMR- and FT-IR spectroscopy in order to evaluate their purity and distribution of functional groups within the modified anhydroglucose unit (AGU). Tosylation of cellulose in mixtures of IL and a co-solvent was found to result in predominant substitution at the primary hydroxyl group. Size exclusion chromatography (SEC) revealed only a moderate degradation of the polymer backbone at a reaction time of 4-8h. Finally, the nucleophilic displacement (SN) of tosyl- and chloro-deoxy groups by azide as well as recycling of the ILs was studied.

Topics: Acetamides; Allyl Compounds; Cellulose; Chromatography, Gel; Dimethyl Sulfoxide; Ethylamines; Imidazoles; Ionic Liquids; Lithium Chloride; Magnetic Resonance Spectroscopy; Organophosphates; Pyridines; Solvents; Spectroscopy, Fourier Transform Infrared; Tosyl Compounds