Electrochemical Incorporation of Carbon Dioxide into Fluorotoluene Derivatives under Mild Conditions

One of the main challenges to combat climate change is to eliminate or reuse Carbon dioxide (CO2), the largest contributor to the greenhouse gases that cause global warming. It is also important to synthesize compounds through greener technologies in order to obtain more environmentally friendly solutions. This study describes the electrocarboxylation process of α,α,α-trifluorotoluene using different working electrodes (glassy carbon, silver and copper) and electrolytes (polar aprotic solvent and ionic liquid). Carboxylated compounds were obtained in the same way in both electrolytic medias with more than 80% conversion rates, high yields, good selectivity, and moderate efficiencies using silver and copper as cathodes in organic electrolytes and ionic liquids.

Hyaluronic Acid Functionalization with Jeffamine® M2005: A Comparison of the Thermo-Responsiveness Properties of the Hydrogel Obtained through Two Different Synthesis Routes

Hyaluronic acid (HA) of different molar masses (respectively 38,000, 140,000 and 1,200,000 g.mol−1) have been functionalized with a commercial poly(etheramine), Jeffamine® M2005, in order to devise physical thermo-responsive hydrogels. Two routes have been studied, involving the use of either water for the first one or of N,N’-Dimethylformamide (DMF), a polar aprotic solvent, for the second one. In the case of the water route, the reaction was performed using a mixture of N-(3-Dimethylaminopropyl)-N’-ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS) as coupling reagents. The reaction was optimized while making sure no free M2005 remained in the final material, leading to M2005 grafting degrees of about 4%, which enabled the formation of hydrogels by increasing the temperature. In the case of the organic solvent route, propylphosphonic anhydride T3P® was used as a coupling reagent in DMF, resulting in a M2005 grafting degree of around 8% with better thermo-responsive properties of HA-g-M2005 compared to those obtained when the reaction was performed in water. However, the reaction systematically led to covalent cross-linking in the case of the HA, with the highest starting molar masses resulting in a very different rheological behaviour and with higher gel strength retaining thermo-responsive behaviour but being only poorly soluble in water.

Dissolution Behavior of Cellulose In The Binary Solvent of Polar Aprotic Solvent And TBAA

We have found that cellulose could be dissolved rapidly in the binary solvent of polar aprotic solvents (PAS) and tetrabutylammonium acetate (TBAA) in a high solubility. The polar aprotic solvents includes dimethyl sulfoxide, pyridine, dimethylacetamide, dimethylformamide and N-Methyl-2-pyrrolidone. The factors affecting the dissolution behavior of cellulose was investigated and it is indicated that the solubility and dissolution rate of cellulose in the binary solvent are significantly dependent on the species of PAS and the molar ratio of PAS/TBAA. Among all the polar aprotic solvents, dimethyl sulfoxide is the best one, being attributed to its high diffusivity and strong solvation ability. The optimal molar ratio of PAS/TBAA was determined by donor number of the polar aprotic solvents. The dissolution of cellulose in the binary solvent was proposed to involve three processes, namely solvent diffusion, solvation of TBAA as well as disruption of the intermolecular or intramolecular hydrogen bonds (H-bonds) of cellulose.

Rationalization of the effects of hydrogen bond donor solvent and nucleofugicity of fluoride ion on nucleophilic aromatic substitution reactions in non-polar aprotic solvent: reaction of 2,4-dinitrofluorobenzene with cyclohexylamine in toluene and toluene

The kinetics of the reaction of 2,4-dinitrofluorobenzene with cyclohexylamine were studied at different concentrations in toluene and toluene-alkanol mixtures. The reaction was not base-catalysed in toluene. Addition of small amounts of hydrogen-bond donor solvent, alkanol (ranging from methanol to hexanol) to the toluene medium of the reactions produced a different effect in comparison to uncatalysed reactions — slight increase in rate of reaction. The results are rationalized in terms of the effect of amine-solvent interaction on the nucleophilicity of the amine in addition to some other factors operating through cyclic transition states leading to products. It is also attributed to the peculiar nature of fluoride ion as a leaving group.