Alternative reaction conditions, Green

Alternative reaction conditions. Green Chemistry, 132-175 Alternative syntheses characterization, 223-227 computer generation of synthesis routes, 215-218... 

Keywords Green chemistry alternative feedstocks benign reagents catalytic synthetic pathways natural processes biocatalysis alternative solvents safer chemicals alternative reaction conditions minimization of energy consumption... 

Alternative Reaction Conditions. The conditions that are used in synthesizing a chemical can have a significant effect on the pathway s overall environmental impact. Considerations of the amount of energy us by one process versus another is quite easily evaluated in economic terms but is not currently as easily evaluated in environmental terms. It appears that because of this difficulty in measurement, and not necessarily as a judgement on relative importance, that the majority of Green Chemistry research on reaction conditions has been centered around the substances utilized as part of those conditions. 

Another interesting alternative combines catalysis and electrochemistry [35]. In the reductive coupling cycle of two bromobenzene molecules to biphenyl, the Pd catalyst provides just two electrons. This reaction can be performed in an electrochemical cell, where the electrons are supplied from an outside source [36]. We thus see that catalysis gives us a variety of green alternatives to the classic stoichiometric process. There are no hard and fast rules as to which route to choose - it all depends on the reaction conditions, and on the chemicals available. 

Biocatalysis has many advantages in the context of green chemistry, e.g. mild reaction conditions and often fewer steps than conventional chemical procedures because protection and deprotection of functional groups are often not required. Consequently, classical chemical procedures are increasingly being replaced by cleaner biocatalytic alternatives in the fine chemicals industry (see later). 

Enzyme-catalyzed reactions based on such biphasic systems have been shown to be promising alternatives for developing green chemical processes because of their physical and chemical characteristics [9]. By combining these media with enzymes, the possibilities of carrying out integral green biocatalytic processes has been already demonstrated [10-12]. Such biphasic systems can be used for both the biotransformation and extraction of products simultaneously, even under extremely harsh conditions, because of the different miscibilities of ILs and SC-CO2. 

Dandia A, Singh R, Jain AK et al (2008) Versatility of alternative reaction media water-mediated domino and green chemical synthesis of pyrimido[l, 2-a]benzimidazole under nonconventional conditions. Synth Commun 38 3543-3555... 

The Future of Glycerol New Uses of a Versatile Raw Material 2 Alternative Solvents for Green Chemistry 3 Eco-Friendly Synthesis of Fine Chemicals 4 Sustainable Solutions for Modern Economies 5 Chemical Reactions and Processes under Flow Conditions 6 Radical Reactions in Aqueous Media... 

Many of the traditional solvents that are favoured by organic chemists have been blacklisted by international regulations, for instance chlorinated hydrocarbon solvents have been severely curtailed. Thus, the question of the solvent requires a major rethink in terms of green chemistry issues this need is driving the search for alternative reaction media. Such media are the basis of many of the cleaner chemical technologies that have reached commercial development. Typical non-conventional reaction media are supercritical carbon dioxide (31.1 °C, 73 atm)22 and supercritical water (374 °C, 218 atm), water under PjT standard conditions, " room-temperature ionic liquids,up to and including solvent-free conditions. ... 

Biodiesel (long-chain monoalkyl fatty acid esters), a renewable and green fuel, is made from vegetable oil or animal fats. At present, the high cost of biodiesel, of which the raw material amounts to 75%, prohibits its wide application. Compared with chemical method, enzymatic process seems to be a promising alternative because of its mild reaction conditions, easy recovery of product, being free of chemical wastes and low demangding on raw materials, which makes it possible to use waste oil as substrate for enzymatic production of biodiesel. 

Green Solvents/Reaction Conditions Database Provides detailed information about solvents and reaction conditions and supplies selected solvent properties that help to identify alternative, less hazardous solvents. 

A great deal of the environmental concern associated with chemical manufacture comes from not merely the chemicals that are made or the chemicals from which they are made, but from all of the substances associated with their manufacture. In the manufacture, processing, formulation and use of chemical products, there are a variety of associated substances that contribute to the environmental loading from chemical manufacture. The most visible of these associated substances are the solvents used in reaction media, separations and formulations. Many solvents, especially the widely used volatile organic solvents, have come under increased scrutiny and regulatory restriction based on concerns for their toxicity and their contributions to air and water pollution. It is for these economic and environmental reasons that much of the research and development in Green Chemistry reaction conditions is focussed on alternative solvents. 

The "Green solvents/reaction conditions" module contains technical information on green alternatives to traditional solvent systems. Users can search for green substitute solvents based on physicochemical properties. 

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