Green Chemistry (green + chemistry)

Distribution by Scientific Domains
Distribution within Chemistry

Selected Abstracts

Synthetic Applications of Laccase in Green Chemistry

Suteera Witayakran
Abstract Laccases (benzenediol:oxygen oxidoreductase, EC, multi-copper-containing oxidoreductase enzymes, are able to catalyze the oxidation of various low-molecular weight compounds, specifically, phenols and anilines, while concomitantly reducing molecular oxygen to water. Because of their high stability, selectivity for phenolic substructures, and mild reaction conditions, laccases are attractive for fine chemical synthesis. This review provides a discussion of the recent applications of this interesting enzyme in synthetic chemistry, including laccase and laccase-mediator catalyzed reactions. In addition, the review also includes a brief discussion of the distribution of laccase in nature, enzyme structure, and the catalytic mechanism which are of relevance to their applications as biocatalysts. [source]

ChemInform Abstract: 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) and Microwave-Accelerated Green Chemistry in Methylation of Phenols, Indoles, and Benzimidazoles with Dimethyl Carbonate.

CHEMINFORM, Issue 21 2002
Wen-Chung Shieh
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Green chemistry for the second generation biorefinery,sustainable chemical manufacturing based on biomass

James H Clark
The material needs of society are reaching a crisis point. The demands of a growing and developing world population will soon exceed the capacity of our present fossil resource based infrastructure. In particular, the chemical industry that underpins most industries needs to respond to these challenges. The chemical manufacturing and user industries face an unprecedented range and intensity of drivers for change, the greatest of which, REACH (Registration, Evaluation and Authorisation of Chemicals) has yet to bite. In order to address the key issues of switching to renewable resources, avoiding hazardous and polluting processes, and manufacturing and using safe and environmentally compatible products, we need to develop sustainable and green chemical product supply chains. For organic chemicals and materials these need to operate under agreed and strict criteria and need to start with widely available, totally renewable and low cost carbon,the only source is biomass and the conversion of biomass into useful products will be carried out in biorefineries. Where these operate at present, their product range is largely limited to simple materials (e.g. cellulose), chemicals (e.g. ethanol) and bioenergy/biofuels. Second generation biorefineries need to build on the need for sustainable chemical products through modern and proven green chemical technologies such as bioprocessing, controlled pyrolysis, catalysis in water and microwave activation, in order to make more complex molecules and materials on which a future sustainable society will be based. Copyright 2007 Society of Chemical Industry [source]

Supramolecular Dye Laser with Cucurbit[7]uril in Water

CHEMPHYSCHEM, Issue 1 2007
Jyotirmayee Mohanty Dr.
Green chemistry: A highly-efficient (,20,%) supramolecular dye laser, with excellent beam quality, is achieved by addition of the macrocyclic host molecule cucurbit[7]uril (CB7) to aqueous solutions of rhodamine 6G (see figure). In direct comparison to the conventional use of ethanol as solvent, the addition of CB7 improves also the photostability and thermo-optical behavior of the laser medium. [source]

Multicomponent Reactions of 1,3-Cyclohexanediones and Formaldehyde in Glycerol: Stabilization of Paraformaldehyde in Glycerol Resulted from using Dimedone as Substrate

Minghao Li
Abstract Glycerol has proved to be an effective promoting medium for many multicomponent reactions of 1,3-cyclohexanediones and formaldehyde. Styrenes, amines, 2-naphthol, 4-hydroxy-6-methyl-2-pyrone and 4-hydroxy-1-methyl-2-quinolone could easily react with 1,3-cyclohexanediones and paraformaldehyde in glycerol under catalyst-free conditions to afford a variety of complex skeletons in fair to excellent yields. In these reactions, glycerol not only showed a significant promoting effect on the reaction yields but also endowed the reaction system with many typical properties of green chemistry, such as cheap, renewable, recyclable and biodegradable solvent, good safety and easy separation of product. The promoting effect of glycerol for the three-component reaction of styrene, dimedone and paraformaldehyde could be attributed to a restricted formation of the methylene intermediate in glycerol. During the reaction, a physical shell, which is mainly composed of a by-product generated in the beginning of the reaction, might be formed in the surface of paraformaldehyde and plays a key role in controlling the formation of the intermediate by means of restricting the decomposition of paraformaldehyde. [source]

Ketonization of 1,5-Cyclooctadiene by Nitrous Oxide

Abstract The kinetics and mechanism of the liquid phase ketonization of 1,5-cyclooctadiene (COD) by nitrous oxide have been studied. The reaction proceeds without catalyst in the temperature range 473,553,K with the activation energy 113,kJ,mol,1 and is first order with respect to the initial reactants. The mechanism includes consecutive ketonization of two CC bonds in the COD molecule, with the intermediate formation of an unsaturated monoketone (MK). Further ketonization of MK leads to two isomeric diketones (DK): 1,4- and 1,5-cyclooctanedione. The 1,5-DK is a stable final product while the 1,4-DK undergoes further intramolecular aldol transformation leading to two bicyclic compounds, that retain the same number of carbon atoms. The distribution of mono- and diketones in the course of reaction is described by theoretical dependences pointing to identical reactivities of the CC double bonds residing in COD and MK molecules. The ketonization of COD by nitrous oxide exemplifies a prospective way for the preparation of valuable organic products in perfect harmony with the strategy of green chemistry. [source]

Enzymatic Production of l -Menthol by a High Substrate Concentration Tolerable Esterase from Newly Isolated Bacillus subtilis ECU0554

Gao-Wei Zheng
Abstract Enzymatic preparation of l -menthol has been attracting much attention in the flavor and fragrance industry. A new ideal strain, Bacillus subtilis ECU0554, which exhibited high hydrolytic activity and excellent enantioselectivity towards l -menthyl ester, has been successfully isolated from soil samples through enrichment culture and identified as Bacillus subtilis by 16S rDNA gene sequencing. The esterase extracted from B. subtilis ECU0554 (BSE) showed the best catalytic properties (E>200) for dl -menthyl acetate among the five menthyl esters examined. Enantioselective hydrolysis of 100,mM dl -menthyl acetate at 30C and pH,7.0, using crude BSE as biocatalyst and 10% ethanol (v/v) as cosolvent, resulted in 49.0% conversion (3,h) and 98.0% ee for the l -menthol produced, which were much better than those using commercial enzymes tested. Moreover, BSE exhibited strong tolerance against high substrate concentration (up to 500,mM), and the concentration of l -menthol produced could reach as high as 182,mM, and more importantly, the optical purity of l -menthol produced was kept above 97% ee, which were not found in previous reports. These results imply that BSE is a potentially promising biocatalyst for the large-scale enzymatic preparation of l -menthol. Using this excellent biocatalyst, the enzymatic production of l -menthol will become a mild, efficient, inexpensive and easy-to-use "green chemistry" methodology. [source]

Heterocyclic synthesis: A convenient route to some 2-mercepto 1,3,4-oxadiazole and green chemistry microwave-induced one-pot synthesis of 2-aryl 1,3,4-oxadiazole in quinazolone and their antibacterial and antifungal activity

A. R. Desai
Several 6-substituted-3-[(5-mercepto-1,3,4-oxadiazol-2-yl)methyl]-2-substituted quinazolin-4(3H)-one or 6-substituted-3-[4-(5-mercepto-1,3,4-oxadiazol-2-yl)phenyl]-2-substituedquinazolin-4(3H)-one 2(a-l) and 6-substituted-3-[(5-phenyl-1,3,4-oxadiazol-2-yl)methyl]-2-substitutedquinazolin-4(3H)-one or 6-substi-tuted-3-[4-(5-phenyl-1,3,4-oxadiazol-2-yl) phenyl]-2-substitutedquinazolin-4(3H)-one 3(a-l) were synthesized using conventional and microwave techniques respectively and were screened for antibacterial and antifungal activity. [source]

Performance of electrospun nanofibers for SPE of drugs from aqueous solutions

Xue-jun Kang
Abstract A novel extraction technique was reported. The solid phase material, nanofiber, was prepared by electrospinning using polystyrene. Twenty different drugs (10 ,g/L in water) were extracted using 1 mg of nanofibers within 5 min. The analytes can be desorpted from the fibers with 50 ,L of the methanol and then monitored by LC coupled to a UV detector. Packed-fiber SPE (PFSPE) provide high recoveries (>50%) for some relatively non-polar drugs (log P >1.5) (n -octanol-to-water partition ratio), and relatively low recoveries (9.9,39.8%) for the drugs within the log P window below 1. Experimental optimization of the technique has been carried out using seven representative drugs, edaravone, cinchonine, quinine, voriconazole, chlordiazepoxide, verapamil, and rutonding. Except for edaravone, the maximum yields of seven drugs (0.2 ,g/L) from water samples were approximately 100%, and were 33.7,88.2% from human plasma. The advantageous aspect of the technique encompasses high throughput, high sensitivity, simplicity, low cost, and green chemistry. [source]

Single-Mode Microwave Ovens as New Reaction Devices: Accelerating the Living Polymerization of 2-Ethyl-2-Oxazoline

Frank Wiesbrock
Abstract Summary: The ring-opening cationic polymerization of 2-ethyl-2-oxazoline was performed in a single-mode microwave reactor as the first example of a microwave-assisted living polymerization. The observed increase in reaction rates by a factor of 350 (6 h,,,1 min) in the range from 80 to 190,C could be attributed solely to a temperature effect as was clearly shown by control experiments and the determined activation energy. Because of the homogenous microwave irradiation, the polymerization could be performed in bulk or with drastically reduced solvent ratios (green chemistry). Monomer conversion, represented by the ratio ln{[M0]/[Mt]}, plotted against time for six temperatures in the range from 80 to 180,C, and polymerization reaction vials, showing an increase in yellow color for those reactions performed (well) above and below 140,C, indicating side reactions. [source]

An overview of inherently safer design,

Dennis C. Hendershot
Inherently safer product and process design represents a fundamentally different approach to safety in the manufacture and use of chemicals. The designer is challenged to identify ways to eliminate or significantly reduce hazards, rather than to develop add-on protective systems and procedures. In the chemical process industries, risk management layers of protection are classified as inherent, passive, active, and procedural. Inherently safer design focuses on eliminating hazards, or minimizing them significantly, to reduce the potential consequence to people, the environment, property, and business. Inherently safer design is considered to be the most robust way of dealing with process risk and can be considered to be a subset of green chemistry and green engineering. It focuses on safety hazards,the immediate impacts of single events such as fires, explosions, and short-term toxic impacts. Many of the strategies of inherently safer design are not specific to the chemical industry, but apply to a broad range of technologies. Strategies for identifying inherently safer options are discussed, with examples. However, for most facilities, a complete risk management program will include features from all categories of layers of protection. Also, the designer must be aware that all processes and materials have multiple hazards and that there can be conflicts among the risks associated with different alternatives. Design alternatives that reduce or eliminate one hazard may create or increase the magnitude of others. Recognition and understanding of these conflicts will enable the designer to make intelligent decisions to optimize the design. 2006 American Institute of Chemical Engineers Process Saf Prog, 2006 [source]

The integration of green chemistry into future biorefineries

James H. Clark
Abstract The use of biorefineries for the production of chemicals as well as materials and energy products is key to ensuring a sustainable future for the chemical and allied industries. Through the integration of green chemistry into biorefineries, and the use of low environmental impact technologies, we can establish future supply chains for genuinely green and sustainable chemical products. The first step in these future biorefineries should be the benign extraction of surface chemicals; here the use of greener solvents, such as supercritical carbon dioxide and bioethanol, should be considered. The residues will often be rich in lignocellulosics and the effective separation of the cellulose is a major challenge which may, in the future, be assisted by greener solvents, such as ionic liquids. Lignin is nature's major source of aromatics; we need new ways to produce small aromatic building blocks from lignin in order to satisfy the enormous and diverse industrial demand for aromatics. Fermentation can be used to convert biomass into a wide range of bioplatform chemicals in addition to ethanol. Their green chemical conversion to higher value chemicals is as important as their efficient production; here clean technologies such as catalysis , notably biocatalysis and heterogeneous catalysis , the use of benign solvents, and energy efficient reactors are essential. Thermochemical processes for the conversion of biomass, such as the production of pyrolysis oil, will also play an important role in future biorefineries and here again green chemistry methods should be used to go to higher value downstream chemicals. Published in 2008 by John Wiley & Sons, Ltd [source]

Graphite-Supported Gold Nanoparticles as Efficient Catalyst for Aerobic Oxidation of Benzylic Amines to Imines and N -Substituted 1,2,3,4-Tetrahydroisoquinolines to Amides: Synthetic Applications and Mechanistic Study

Man-Ho So
Abstract Selective oxidation of amines using oxygen as terminal oxidant is an important area in green chemistry. In this work, we describe the use of graphite-supported gold nanoparticles (AuNPs/C) to catalyze aerobic oxidation of cyclic and acyclic benzylic amines to the corresponding imines with moderate-to-excellent substrate conversions (43,100,%) and product yields (66,99,%) (19,examples). Oxidation of N -substituted 1,2,3,4-tetrahydroisoquinolines in the presence of aqueous NaHCO3 solution gave the corresponding amides in good yields (83,93,%) with high selectivity (up to amide/enamide=93:4) (6,examples). The same protocol can be applied to the synthesis of benzimidazoles from the reaction of o -phenylenediamines with benzaldehydes under aerobic conditions (8,examples). By simple centrifugation, AuNPs/C can be recovered and reused for ten consecutive runs for the oxidation of dibenzylamine to N -benzylidene(phenyl)methanamine without significant loss of catalytic activity and selectivity. This protocol "AuNPs/C+O2" can be scaled to the gram scale, and 8.9,g (84,% isolated yield) of 3,4-dihydroisoquinoline can be obtained from the oxidation of 10,g 1,2,3,4-tetrahydroisoquinoline in a one-pot reaction. Based on the results of kinetic studies, radical traps experiment, and Hammett plot, a mechanism involving the hydrogen-transfer reaction from amine to metal and oxidation of M-H is proposed. [source]

Methyltrioxorhenium Catalysis in Nonconventional Solvents: A Great Catalyst in a Safe Reaction Medium

Marcello Crucianelli Dr.
Abstract The requirement that chemical processes are sustainabable, reflected in waste reduction and the use of safe reagents and reaction conditions, is becoming even more stringent as a result of pressure by society and governments to preserve the environment and protect human health. Catalysis offers numerous benefits related to green chemistry, including lowered energetic reaction requirements; catalytic, rather than stoichiometric, amounts of materials; increased selectivity; lowered consumption of processing and separation agents; and, in many cases, the use of less-toxic compounds. Our research group has for a long time been studying methyltrioxorhenium in the oxyfunctionalization of different substrates, by using H2O2 or its urea-hydrogen peroxide complex as the primary oxidant. In this Review paper we aim to provide a full literature account on the catalytic activity and selectivity of methyltrioxorhenium in the oxyfunctionalization reaction, either in nonconventional solvents or under solvent-free conditions, with a particular emphasis on the use of ionic liquids as green reaction media. [source]

Molecularly imprinted polymers as a tool for separation in CEC

Zhao-Sheng Liu Dr.
Abstract Molecularly imprinted polymers (MIPs) are synthesized in the presence of a template which results in the formation of specific recognition cavities complementary to the template in shape and chemical functionality. One of the most successful application areas of MIPs is chromatographic sorbents, which are tailor-made synthetic polymers for a given analyte. However, low efficiency of MIP columns is often observed because of slow kinetics of the template. CEC-based MIPs are thought to improve efficiency of MIP-based separation due to the enhanced flow dynamics of CEC. Another attractive feature is the miniaturized format of CEC, so that fewer templates or monomers for the molecular imprinting are consumed, a characteristic desired for ,green chemistry'. The small dimensions of a capillary demand the development of novel polymer formats that can be applied to a miniaturized system. This review discusses the various formats, i.e., the micro- or nanoparticle, the coating and the monolith, for application in CEC as well as the use in MIP syntheses and characteristics. [source]

Cover Picture: Biotechnology Journal 5/2006

Article first published online: 11 MAY 200
Cover illustration: Chirality is omnipresent in nature: Many compounds contain an asymmetric center and thus can occur in two non-superimposable mirror-image forms (enantiomers). The two enantiomers of a chiral compound often have dramatically different effects, as exemplified by the thalidomid catastrophe. Therefore, only one enantiomer is needed for the production of active substances in the pharmaceutical or agricultural industry. It is an important aspect in white biotechnology, to take advantage of highly specific catalysts of (micro-) biological origin for the synthesis of enantiopure compounds. Biocatalysis indeed is a highly efficient process and an example of environmentally friendly, ,green' chemistry, requiring relatively low energy inputs, mild solvents and generating minimal byproducts. Image Wacker. [source]