Electrochemistry biocatalysis

New methodologies in the synthesis of total synthesis (photochemistry, electrochemistry, biocatalysis, etc.)... 

This chapter is intended to cover the progress made in the study of the physicochemical properties of DESs and their applications as environmentally-friendly reaction media in a variety of chemical applications (i.e., electrochemistry, biocatalysis, metal extraction, material chemistry, and metal-catalyzed organic reaction). As this is a fast growing and widespread field, the author will try to give a general trend of this research area. 

There is huge potential in the combination of biocatalysis and electrochemistry through reaction engineering as the linker. An example is a continuous electrochemical enzyme membrane reactor that showed a total turnover number of 260 000 for the enantioselective peroxidase catalyzed oxidation of a thioether into its sulfone by in situ cathodic generated hydrogen peroxide - much higher than achieved by conventional methods [52],... 

Wang, S.F., Chen, T., Zhang, Z.L., Pang, D.W., and Wong, K.Y., Effects of hydrophobic room-temperature ionic liquid l-butyl-3-methylimidazolium tetrafluoroborate on direct electrochemistry and biocatalysis of heme proteins entrapped in agarose hydrogel films, Electrochem. Commun., 9, 1709-1714, 2007. 

Alternative synthetic pathways based on atom (and mass) economy, achievable through catalysis and biocatalysis, natural processes, such as photochemistry, electrochemistry and biomimetic synthesis. 

Especially, the eco-friendly ionic liquids have obtained extensive attention in organic synthesis with the merits provided as above. The ionic liquids as the unusual green solvents are applied extensively in various organic synthesis reactions, such as Friedel-Crafts reactions, oxidation reactions, reduction reactions, addition reactions, C-C formation reactions, nucleophilic substitution reactions, esterifications, rearrangements, hydroformylations, and nitration reactions [7-14]. Besides, the ionic liquids also have applications in the extraction separation, the electrochemistry, and preparation of nanostructured materials, the production of clean fuel, environmental science, and biocatalysis. This chapter would present in detail the application of the ionic liquids as the unusual green solvents (also as dual green solvent and catalyst) for the alkylation and acylation. 

The interest in ILs has been generated due to their unique properties and potential uses in areas as diverse as synthesis, biocatalysis, electrochemistry, etc. Thus, this class of molecules is increasingly employed in organic chemistry, material sciences and physical chemistry [3,4], ILs are salts - substances composed exclusively of cations and anions. This fact differentiates them from simple ionic solutions, in which ions are dissolved in a molecular medium. They are also different from inorganic molten salts because their melting points are lower than 100°C (most of them exist in liquid form at or near room temperature). 

During 2003 we saw the first published process based on ILs [6], In its BASIL process (see Section 5.3.2), BASF has disclosed the involvement of an imidazolium-based ionic-liquid in the production of alkoxyphenylphosphines. This constitutes an impressive demonstration that IL technology can result in significant financial savings. Another process said to be poised for licensing is the French Petroleum Institute s butene dimerization process, the Difasol process (see Section 5.3.1). Besides these, some more promising applications are currently under investigation, and are hoped to be disclosed in the near future. Notable examples of research areas are in electrochemistry (batteries), biocatalysis, and the application of ILs in extraction processes, e.g., the deep desulfurization of diesel oil. 

Carboxymelhylated chitosan (CM-chitosan) has a similar molecular structure with amino acids and can be obtained by carboxymethylated reactions between chitosan and monochloroacetic acid [57]. Chitosan and CM-chitosan are attractive nontoxic, biocompatible, biodegradable, and film-forming biomaterials that can be used as biosensors and biocatalysis [58]. Despite a composite system based on chitosan and RTILs for electrochemistry applications presented by Lu et al. [59], to date, there are no other reports on the synthesis of ionic liquids composed of natural oligosaccharides. Furthermore, it will be helpful to improve the biocompatibility of ionic liquid by introducing CM-chitosan as an anion compound. Recently, RTIL based on l-ethyl-3-methylimidazolium hydroxide, [C2mim][OH], and CM-chitosan was prepared by a neutralization reaction (Fig. 7.7) [57]. 

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