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Environmentally benign media

Catalysts and their effects on chemical reactions aid in efficiency, effectiveness and selectivity. A recent example of current research is redox and ligand exchange reactions of the oxygenation catalyst (N,N -bis(salicylidene)ethylenediaminato)co-balt(II), Co(SALEN)2 (below), and its one-electron oxidation product, Co(salen) 2-These were investigated in DMF, pyridine, and mixtures of these solvents. Solvent effects on the potentials, the thermodynamics of cross reactions, and the distribution of Co(II) and Co(III) species as a function of the solvent composition are important considerations (Eichhorn, 1997). The results in these solvents should be compared with other work with catalysts using more environmentally benign media (Collins et al., 1998). [Pg.28]

Recently, applications of lion-aqueous solutions in the field of modern electrochemical technologies are increasing. Books [1] and review articles [2] that deal with the technological aspects of non-aqueous electrochemistry have appeared. In this chapter, examples of such applications of non-aqueous solutions are outlined. In the last section, the electrochemical use of supercritical fluids and ionic liquids as environmentally benign media is also discussed. [Pg.313]

Some supercritical fluids and room temperature ionic liquids are attracting attention as environmentally benign media for extractions, separations and chemical reactions. This section outlines their applications as electrochemical solvents. [Pg.326]

In the last decade, a lot of attention has been paid to environmental aspects. As to the Mizoroki-Heck reaction, environmentally benign media currently involved in the design of catalytic systems encompass supercritical carbon dioxide (scCOa), fluorous systems, water and aqueous systems, solvent-free systems [66]. In this context, it should be noted that the so-called solvent-free reactions are actually not literally such, but are performed in media composed of substrates and often liquid amine. This was described as early as in 1972 by Heck himself [2, 8] (microwave heated version [53]). Amines are good coordinating solvents during the reaction, the amine is transformed into amine salt, which, being a major constituent or reaction mixture in the absence of a true solvent, adds to the net media polarity. [Pg.64]

Ionic liquids have been recognized as designer solvents and are now accepted as environmentally benign media in a number of chemical transformations. Their property of acting as heterogeneous catalysts in aldol condensations (Abello et al. 2004) and transesteriflcation (Liu et al. 2012) has emerged as an area of great interest. [Pg.296]

Reddy, V.S. Katti, K.V. Barnes, C.L. (1995) Chemistry in environmentally benign media. 1. Synthesis and characterization of l,2-bis(bis(hydroxymethyl)phosphino)ethane (HMPE) X-ray structure of [Pt((H0H2C)2PCH2CH2P(CH20H)2)2]Cl2, Inorg. Chim. Acta, 240, 367-70. [Pg.214]

Ionic liquids (IL) have received much attention due to their unique properties such as nonvolatility, nonflammability, reusability, and great potential as environmentally benign media [81]. Some of the ionic liquids have been... [Pg.233]

PTC in SCF solvents offers a plethora of opportunities. Certainly the technique will be both applicable and us ul for a wide variety of reactions. With opportunities to tune selectivity, enhance transport, and to remove solvents, all in an environmentally benign medium, this emerging area of research has great potential. With the recent surge of interest in developing technologies for a sustainable society, PTC/SCF systems can play an important role in industrial ecology. [Pg.453]

Environmentally green solvents. Supercritical carbon dioxide presents an environmentally benign medium for polymerizations (and other chemical operations), minimizing pollution from organic solvents and facilitating the isolation of the polymeric product. [Pg.782]

After the seminal work reported by Satoh and Miura in early 2011 on ruthenium-catalyzed oxidative vinylation of heteroarene carboxylic acids with alkenes [17], Ackermann demonstrated a ruthenium(ll)-catalyzed cross-dehydrogenative C-H bond alkenylations of benzoic acid derivatives with acrylonitrile or alkyl acrylates. Following the oxidative C—H bond alkenylation reaction, subsequent intramolecular oxa-Michael reaction occurred leading to phthalides in good yields (Eq. (7.12)) [18]. The reactions took place with water as an environmentally benign medium under mild conditions. [Pg.198]

In addition to the environmentally benign attributes and the easily tunable solvent properties, other important characteristics such as low interfacial tension, excellent wetting behavior, and high diffusion coefficients also make SCCO2 a superior medium for the synthesis of nanoscale materials [2]. Previous works on w/c RMs showed that conventional hydrocarbon surfactants such as AOT do not form RMs in scCOi [3] AOT is completely insoluble in CO2 due to the poor miscibility of the alkyl chains with CO2, restricting the utilization of this medium. Recently, we had demonstrated that the commonly used surfactant,... [Pg.729]

In recent years, supercritical fluids such as scC02 were considered to be modern green solvents they were non-toxic, readily available, inexpensive, and environmentally benign. They are studied as a reaction medium for catalytic applications because of their interest in product separation and catalyst recovery, and... [Pg.236]

More recently, an environmentally benign method using air as oxidant has been developed for the oxidative cyclization of arylamine-substituted tricarbonyl-iron-cyclohexadiene complexes to carbazoles (Scheme 19). Reaction of methyl 4-aminosalicylate 45 with the complex salt 6a affords the iron complex 46, which on oxidation in acidic medium by air provides the tricarbonyliron-complexed 4a,9a-dihydrocarbazole 47. Aromatization with concomitant demetalation by treatment of the crude product with p-chloranil leads to mukonidine 48 [88]. The spectral data of this compound are in agreement with those reported by Wu[22j. [Pg.130]

Kabalka and co-workers reported the direct cross-coupling of cinnamyl alcohols with aryl- and vinylboronic acids using simple rhodium salts in an environmentally benign ionic liquid medium (Eq. 6) [30]. The ability to utilize allylic alcohols, without activation, is significant from the viewpoint of atom economy, yet challenging due to the poor leaving group ability of hydroxide. [Pg.200]

Water is cheap, relatively abundant in many part of the world, safe, and, when pure, environmentally benign [40]. It is also true that some reactions show unusual selectivity and/or rate enhancements when run in, or more accurately, on water [41]. However, a closer examination of many reactions in water reveals that in fact one or more liquid reagents have been used in large excess, so they are in fact biphasic reactions. There is also a misguided perception that water, after use as a reaction medium, can be poured down the drain [42]. On an industrial scale, there can be a considerable cost and environmental burden associated with remediation of waste water streams contaminated with solvents and organic and metal residues-see Chapters 2 and 3. [Pg.345]

The desire for a sustainable development in chemistry lays the foundation for environmentally benign processes. From the view point of organic chemistry, the construction of carbon skeletons plays the pivotal role. The extraordinarily mild reaction conditions in addition to the non-toxic and non-bumable properties and ubiquitous availability of water as the reaction medium make enzyme-catalyzed C-C-bond formation the first choice even for industrial production. Thanks to subtle selectivity features of the corresponding enzymes a rather broad range in substrate specificity meets with a highly conserved stereospecificity at the newly connected carbon centers. In addition, these features and the availability of the respective biocatalysts are open to intervention by recombinant genetechnological techniques. [Pg.210]

The procedure towards an environmentally benign process starts with the selection of raw materials in addition to conventional raw materials from the petrochemical industry based on low- to medium-boiling aliphatic and aromatic hydrocarbons, replenishable raw materials from nature are increasingly available nowadays. In the simplest cases, these can be carbon sources, such as glucose and sucrose for fermentation, but also more complex molecules, frequently obtained from the chiral pool or through inexpensive fermentation from carbon sources, such as glutamic acid or citric acid. Table 20.2 lists a selection of raw materials from the chiral pool, with their estimated costs per kilogram. [Pg.576]

The environmentally benign, nontoxic, and nonflammable fluids water and carbon dioxide (C02) are the two most abundant and inexpensive solvents on Earth. Water-in-C02 (w/c) or C02-in-water (c/w) dispersions in the form of microemulsions and emulsions offer new possibilities in waste minimization for the replacement of organic solvents in separations, reactions, and materials formation processes. Whereas the solvent strength of C02 is limited, these dispersions have the ability to function as a universal solvent medium by solubilizing high concentrations of polar, ionic, and nonpolar molecules within their dispersed and continuous phases. These emulsions may be phase-separated easily for product recovery (unlike the case for conventional emulsions) simply by depressurization. [Pg.135]

Over the past decade, carbon dioxide has become an attractive alternate solvent for a variety of polymer synthesis and processing applications due to its environmentally benign nature and chemical inertness I T Properties of CO2, such as dielectric constant and density are sensitive to the temperature and pressure of the system. The fluid density and dielectric constant, can be fine tuned using temperature and pressure profiling. In addition, CO2 offers an environmentally sound medium with the potential to eliminate organic and aqueous waste streams in manufacturing facilities. [Pg.23]

Leitner, W. Carbon dioxide as an environmentally benign reaction medium for chemical synthesis. Appl. Organomet. Chem. 2000, 14, 809-814. [Pg.2924]

Development of environmentally benign industrial processes utilizing CO2, which is a cheap and safe Ci resource as well as a nontoxic reaction medium, has received much interest. One of the attractive reactions is the synthesis of dimethyl carbonate (DMC) from CO2 and methanol. The reaction is reversible and can be expressed by eqn. (3) ... [Pg.117]


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