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Green solvents: chemistry and applications of ionic liquids in catalysis, colloid chemistry and derivatization of biopolymers


Solvents affect reactions in several ways: It is the agent of heat-, and mass-transfer; It changes the free-energy of activation by solvating the reactants/transition states; It mediates proton transfers for acid-base catalyzed reactions, etc. Green chemistry principles dictate "atom efficiency", process safety, use of renewable starting materials, and production of biodegradable products. Applying these principles requires that: We understand the role of solvent, and the mechanisms of solvation; Optimize the use of solvent in the process; Substitute several solvents in current use (chlorinated; inflammable; high-pressure solvents) with convenient ones. Of these, ionic liquids, ILs, are most promising. The explosive interest in the latter is due to their favorable characteristics. They are polar, chemically- and thermally stable, and have extremely low vapor pressure. More importantly, however, is their structural versatility: an unlimited number of ILs can be synthesized by the combination of the proper cations and anions. On the other hand, ILs are much more expensive than conventional solvents, this calls for use of minimum volume of the IL, coupled with its recycling in the process. The use of solvent mixtures of conventional and green solvents is attractive because the properties of the mixtures can be continuously "tuned" by varying the composition of the mixture. Solvation by mixtures, however, is complex because of the preferential solvation of the solutes by one component of the mixture, and the micro-heterogeneity of these mixtures. The main Project is divided into sub-projects 1 and 2 "Aplication of solvatochromism in catalysis and colloid chemistry" and "cellulose derivatization in homogenneous systems: Use of conventional solvents and ionic liquids", respectively; both will be carried out in the labs of the project coordinator. Sub-projects 3 and 4 "use of electrochemical techniques in the study of micellar systems" and "Rheological behavior of cellulose solutions in conventional solvents and ionic liquids" will be carried out in collaboration with Mauro Bertotti and Elizabeth P. G. Arêas, both Professors of this Institute. (AU)

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