bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactivity of Molecular Dioxygen towards a Series of Isostructural Dichloroiron(III) Complexes with Tripodal Tetraamine Ligands: General Access to μ‐Oxodiiron(III) Complexes and Effect of α‐Fluorination on the Reaction Kinetics
Authors: Thallaj Nasser K. , Rotthaus Olaf , Benhamou Leila , Humbert Nicolas , Elhabiri Mourad , Lachkar Mohammed , Welter Richard , Albrecht‐Gary Anne‐Marie , Mandon Dominique 
Published: June 2008

AbstractWe have synthesized the mono, di‐, and tri‐α‐fluoro ligands in the tris(2‐pyridylmethyl)amine (TPA) series, namely, FTPA, F2TPA and F3TPA, respectively. Fluorination at the α‐position of these nitrogen‐containing tripods shifts the oxidation potential of the ligand by 45–70 mV per added fluorine atom. The crystal structures of the dichloroiron(II) complexes with FTPA and F2TPA reveal that the iron center lies in a distorted octahedral geometry comparable to that already found in TPAFeCl2. All spectroscopic data indicate that the geometry is retained in solution. These three isostructural complexes all react with molecular dioxygen to yield stable μ‐oxodiiron(III) complexes. Crystal structure analyses are reported for each of these three μ‐oxo compounds. With TPA, a symmetrical structure is obtained for a dicationic compound with the tripod coordinated in the κ4N coordination mode. With FTPA, the compound is a neutral μ‐oxodiiron(III) complex with a κ3N coordination mode of the ligand. Oxygenation of the F2TPA complex gave a neutral unsymmetrical compound, the structure of which is reminiscent of that already found with the trifluorinated ligand. On reduction, all μ‐oxodiiron(III) complexes revert to the starting iron(II) species. The oxygenation reaction parallels the well‐known formation of μ‐oxo derivatives from dioxygen in the chemistry of porphyrins reported almost three decades ago. The striking feature of the series of iron(II) precursors is the effect of the ligand on the kinetics of oxygenation of the complexes. Whereas the parent complex undergoes 90 % conversion over 40 h, the monofluorinated ligand provides a complex that has fully reacted after 30 h, whereas the reaction time for the complex with the difluorinated ligand is only 10 h. Analysis of the spectroscopic data reveals that formation of the μ‐oxo complexes proceeds in two distinct reversible kinetic steps with k1≈10 k2. For TPAFeCl2 and FTPAFeCl2 only small variations in the k1 and k2 values are observed. By contrast, F2TPAFeCl2 exhibits k1 and k2 values that are ten times higher. These differences in kinetics are interpreted in the light of structural and electronic effects, especially the Lewis acidity at the metal center. Our results suggest coordination of dioxygen as an initial step in the process leading to formation of μ‐oxodiiron(III) compounds, by contrast with an unlikely outer‐sphere reduction of dioxygen, which generally occurs at negative potentials.
A Materials Approach to Site‐Isolation of Grubbs Catalysts from Incompatible Solvents and m‐Chloroperoxybenzoic Acid
Authors: Mwangi Martin T. , Runge M. Brett , Hoak Kevin M. , Schulz Michael D. , Bowden Ned B. 
Published: June 2008

AbstractThe development of a method for site‐isolation of Grubbs second‐generation catalyst from MCPBA is described. In these reactions, Grubbs catalyst was dissolved in a solvent consisting of a mixture (1:1 v/v) of 1‐butyl‐3‐methylimidazolium hexafluorophosphate and methylene chloride and completely encapsulated within a thimble fabricated from polydimethylsiloxane (PDMS). A series of molecules that react by cross metathesis or ring‐closing metathesis were added to the interior of the thimble and allowed to react. In the last step, m‐chloroperoxybenzoic acid (MCPBA) dissolved in MeOH/H2O (1:1 v/v) was added to the exterior of the PDMS thimble. Small organic molecules diffused through the PDMS to react with MCPBA to form epoxides, but the Grubbs catalyst remained encapsulated. This result is important because Grubbs catalyst catalytically decomposes MCPBA at ratios of MCPBA to Grubbs of 3000 to 1. The yields for this two‐step cascade sequence ranged from 67 to 83 %. The concept behind this sequence is that small organic molecules have high flux through PDMS but large molecules—such as Grubbs catalyst—and ionic reagents—such as MCPBA—have much lower flux through PDMS. Small molecules can thus react both outside and inside PDMS thimbles, whereas incompatible catalysts and reagents remain site‐isolated from each other. This method does not require alteration of structures of the catalysts or reagents, so it may be applied to a wide range of homogeneous catalysts and reagents. To demonstrate further that the catalyst was encapsulated, the Grubbs catalyst was successfully recycled within the cascade sequence.
Thermal Isomerization of (+)‐cis‐ and (−)‐trans‐Pinane Leading to (−)‐β‐Citronellene and (+)‐Isocitronellene
Authors: Stolle Achim , Ondruschka Bernd , Bonrath Werner , Netscher Thomas , Findeisen Matthias , Hoffmann Markus M. 
Published: June 2008

AbstractCatalyzed and uncatalyzed rearrangement reactions of terpenoids play a major role in laboratory and industrial‐scale synthesis of fine chemicals. Herein, we present our results on the thermally induced isomerization of pinane (1). Investigation of the thermal behavior of (+)‐cis‐ (1 a) and (−)‐trans‐pinane (1 b) in a flow‐type reactor reveals significant differences in both reactivity and selectivity concerning the formation of (−)‐β‐citronellene (2) and (+)‐isocitronellene (3) as main products. Possible explanations for these results are discussed on the basis of reaction mechanism and ground‐state geometries for 1 a and 1 b. To identify side reactions caused from ene cyclizations of 2 and 3, additional pyrolysis experiments were conducted that enabled the identification of almost all compounds in the network of C10H18‐hydrocarbon products formed from 1.
Discovery of New Biocatalysts for the Glycosylation of Terpenoid Scaffolds
Authors: Caputi Lorenzo , Lim Eng‐Kiat , Bowles Dianna J. 
Published: June 2008

AbstractThe synthesis of terpenoid glycosides typically uses a chemical strategy since few biocatalysts have been identified that recognise these scaffolds. In this study, a platform of 107 recombinant glycosyltransferases (GTs), comprising the multigene family of small molecule GTs of Arabidopsis thaliana have been screened against a range of model terpenoid acceptors to identify those enzymes with high activity. Twenty‐seven GTs are shown to glycosylate a diversity of mono‐, sesqui‐ and diterpenes, such as geraniol, perillyl alcohol, artemisinic acid and retinoic acid. Certain enzymes showing substantial sequence similarity recognise terpenoids containing a primary alcohol, irrespective of the linear or cyclical structure of the scaffold; other GTs glycosylate scaffolds containing secondary and tertiary alcohols; the carboxyl group of other terpenoids also represents a feature that is recognized by GTs previously known to form glucose esters with many different compounds. These data underpin the rapid prediction of potential biocatalysts from GT sequence information. To explore the potential of GTs as biocatalysts, their use for the production of terpenoid glycosides was investigated by using a microbial‐based whole‐cell biotransformation system capable of regenerating the cofactor, UDP‐glucose. A high cell density fermentation system was shown to produce several hundred milligrams of a model terpenoid, geranyl‐glucoside. The activities of the GTs are discussed in relation to their substrate recognition and their utility in biotransformations as a complement or alternative to chemical synthesis.
A Shift in Retrosynthetic Paradigm
Authors: Marek Ilan 
Published: June 2008

AbstractThe current state‐of‐the‐art synthesis for the formation of enantiomerically enriched all‐carbon quaternary stereocenters in acyclic system relies on the formation of a single carboncarbon bond per chemical step by asymmetric catalysis. These extraordinary sophisticated methods were logically classified among the most powerful and innovative ones. In this concept article, we are proposing a new retrosynthetic paradigm to solve differently such challenging problems. These new synthetic pathways lead to the diastereo‐ and enantiomerically pure formation of three new carboncarbon bonds in acyclic system, in a one‐pot reaction, including the formation of all‐carbon quaternary stereocenters by using classical reagents and experimental conditions and from common starting materials.
Toxicity Assessment of Industrial Effluent by Bioassays
Authors: Sahu Ranjeev K. , Katiyar Shashwat , Yadav Awadhesh K. , Kumar Narendra , Srivastava Jatin 
Published: June 2008

AbstractIn the present study, the toxicity assessment of tannery effluent was carried out in terms of percent phytotoxicity and shoot/root dry weight ratio. The effluent used in the study was collected from the outlet of an effluent treatment plant situated in the Jajmau area of Kanpur, U. P. India. Three varieties each of rice (Surya‐52, Jaya‐14 and Pant‐10), pulses (Lens‐(Type‐9), Gram Bahar, and Mung‐C‐K‐851) and oil seeds (Mustard RS‐30, B‐9 and T‐69) containing different kinds of reserve food materials, i. e., starch, protein and fat were taken for the toxicity study. The accumulations of heavy metals, i. e., Cr, Cu, Zn, and Ni, by these different crop varieties through pot culture irrigated with effluent were estimated at maturity. The concentration of heavy metals in the effluent was found to be Cr = 0.135, Cu = 0.065, Zn = 0.052, and Ni = 0.036 mg/L. The maximum concentration found in the plant tissue was seen in the mustard variety RS 30, i. e., Cr = 15.2, Cu = 4.4, Zn = 3.2, and Ni = 2.6 μg/g dry weight (d.w.) and the minimum concentration was found in Gram Bahar, i. e., Cr = 8.5, Cu = 2.0, Zn = 1.6 μg/g d.w., whereas, in 0.98 μg/g d.w. of Ni was found in the Surya rice variety. The percent phytotoxicity was found to be in the range of 10.4 to 25.6% amongst the different test varieties. The average percent phytotoxicity was found to be highest in rice followed by oilseed and pulses. The shoot/root dry weight ratio ranged between 10.82 to 14.22, with the highest value seen for rice (Pant‐10) and the lowest for a pulse (Gram‐Bahar). The results revealed that cultivation of these crops irrigated with the tannery effluent may pose a potential risk to humans as well as animals because of their bioaccumulation properties and ability to transfer metals from one trophic level to the next trophic level through the food chain. Since the percent phytotoxicity and shoot/root dry weight ratio behaves in a similar manner for the effluent, these parameters can be considered for the assessment of toxicity of industrial effluents.
Sustainability of Biobased and Biodegradable Plastics
Authors: Sudesh Kumar , Iwata Tadahisa 
Published: June 2008

AbstractAdvances in science and technology have resulted in the rapid development of modern society, which is clearly unsustainable because of the strain it places on current resources. The energy and materials needed to sustain the present society are derived primarily from non‐renewable fossil resources, which will be depleted at some point. Plastics are one example of an important commodity in the modern lifestyle. While plastics are undoubtedly superior materials in terms of their costs, processability and functional properties, they are currently derived from fossil resources and they are not readily assimilated by the various ecosystems upon disposal. The search for biodegradable plastics that are derived from renewable resources has been ongoing since the 1970s. Two of the most promising biobased plastics, i. e., polylactic acid and polyhydroxyalkanoates, have received much attention as potential alternatives to existing processes. This article will discuss the current status and sustainability of these two next generation biobased plastics by taking into consideration the raw materials required, as well as the post‐consumption effects of these materials on the environment. In addition, important issues surrounding the development and sustainability of biobased and biodegradable plastics will be highlighted.
Study on Ammonia‐Nitrogen and Humic Acid Removal Using Aluminum Oxide Molecular Sieve and Modified Clinoptilolite
Authors: Liu Chen , Wu Xin‐Wu , Bao Zhi‐Yu , Dong Yan‐Mao 
Published: June 2008

AbstractThe removal of ammonia‐nitrogen (NH4+–N) and humic acid (HA) in water by aluminum oxide molecular sieve (AOMS)/modified clinoptilolite (MC) was investigated using a flow system. The study focuses on the effect of AOMS on the removal of NH4+–N and HA. The dependence of ion‐exchange of MC on the organic contaminants was also investigated. The results show that the NH4+–N is difficult to remove by AOMS only. However, the effective removal of HA by AOMS brings about a higher efficiency of NH4+–N removal by AOMS‐MC, so that the NH4+–N and HA are removed simultaneously.
Environmental Conflicts and Activism with Industrialization in South Korea
Authors: Kim Jung Wk 
Published: June 2008

AbstractWhen South Korea launched the first 5‐year economic development plan in 1962 to industrialize Korea, little attention was given to the environment. The industrialization process has been successful and as a result, the quality of the environment has been continually deteriorating in South Korea resulting in numerous environmental conflicts. The earliest environmental activism that arose was the struggles of the inhabitants in industrial complexes for survival. The government removed inhabitants from the affected areas instead of solving the root causes of the environmental problems. The activism began to disperse into areas surrounding metropolitan cities and industrial areas and even into rural areas as environmentally‐susceptible facilities such as nuclear waste repositories and landfills, which often resulted in violent riots. The environmental conflicts have been aggravated since numerous construction projects have boomed in the country. In particular, the so‐called National Policy Projects such as large‐scale reclamation as well as dam and road construction brought forth nationwide environmental conflicts and activism. Such conflicts often resulted in the breakdown of communities as well as serious economic loss to their inhabitants. Most of these conflicts share common causes, i. e., undemocratic processes in decision making, lack of fair impact assessment procedures, and severe economic loss to the local inhabitants. All of the processes used to resolve the conflicts, e. g., negotiation, mediation, arbitration, and ultimately lawsuits have been painful and costly. Transparency and democracy in the decision‐making process and the fairness in impact assessment are essential to prevent such conflicts or to resolve them. In addition, the voice of the minority victims should not be ignored. In order to ensure this, sustainable governance building is necessary incorporating the government, corporations and citizens. Sustainable development is the key issue to help prevent environmental conflicts arising. There have been positive aspects of the environmental activism, e. g., through the activism, the communities have been strengthened, environmental awareness has risen and social capital has built up.
Air Pollution and Urban Air Quality Management in Indonesia
Authors: Santosa Sri Juari , Okuda Tomoaki , Tanaka Shigeru 
Published: June 2008

AbstractThe trade‐led industry and economic development after the Asian financial crisis a decade ago has been accelerated in Indonesia to improve the quality of life of its population. This rapid development of Indonesia was in fact heavily fueled by fossil fuels, especially oil, followed by natural gas and coal. The exploitation of fossil fuel in fueling the development resulted in significant environmental quality degradation. Air pollution is perhaps Indonesia's most severe environmental problem. Industry and transportation were the typical main sources of urban air pollutants. Moreover, Indonesia also failed to reach its original 2005 target for a complete phase‐out of leaded gasoline. As a result, the level of Pb together with other pollutants such as CO, NOx, SO2, and total suspended particulates has exceeded or at least approached the designated ambient air quality standards. The urban air pollution will not be lesser in extent, but surely will be more severe in the future. Unfortunately, the capability of the Indonesian authorities to manage the urban air quality is still very limited and the portion of the budget allocated to the improvement of urban air quality is still remarkably low, typically 1% of total. This is why the efforts to enhance the capability to manage the urban air quality could not be handled by the environmental authorities in Indonesia's cities themselves, but outside stimulation in the form of man power, consultant and equipment assistance along with financial support has been very important.
Palm Oil Boom in Indonesia: From Plantation to Downstream Products and Biodiesel
Authors: Santosa Sri Juari 
Published: June 2008

AbstractIndonesia has been the biggest producer of palm oil (PO) in the world since 2005. The total production in 2007 was 17.0 and 1.9 million tons of crude palm oil (CPO) and crude palm kernel oil (CPKO), respectively. More than 70% of the CPO was exported and 87% of the domestic consumption was used for food. The production and subsequent refining and fractionation of CPO and CPKO generated biomass by‐products that consists of trunk, frond, empty fruit bunch (EFB), fiber, shell, and palm kernel meal (PKM), and discharged wastes of palm oil mill effluent (POME) as well as palm fatty acid distillate (PFAD). The amount of by‐products and wastes produced has been growing very rapidly and efforts to diversify and improve their utilization are a great challenge. As claimed in many research reports, the by‐products and wastes could be potentially utilized as sources of energy, animal feed, chemicals, paper pulp, advanced materials, medicines and food ingredients. A more important role may be played by PO as the Indonesian Government took further steps in 2006 to become the world's largest producer of biodiesel. As a starting point, Presidential Instruction No. 1/2006 for the Production and Use of Biofuel as Alternative Fuel was issued in January 2006. Responding to this Presidential Instruction, at least 15 companies are planning to establish new larger biodiesel refineries to enhance the currently produced 82.5 million L of biodiesel. It is planned to start production in 2008/2009 with two new refineries that have a total capacity of ca. 1,600 million L/year.
Electrogenerative Processes for Environmental Applications
Authors: Yap Chin Yean , Mohamed Norita 
Published: June 2008

AbstractThe applications of electrogenerative processes which could be an alternative to current environmental treatment technologies are briefly reviewed. This process does not require an external supply of energy due to the spontaneous chemical reaction that takes place in the reactor and generates an external flow of current as a by‐product. The operation is attractive in reducing operational costs, especially when dealing with solutions of low ion concentrations. Electrogenerative reactors which can be operated in various configurations and their designs are described. The rate and selectivity for particular reactions can be controlled by varying electrode potentials and with suitable choices of electrodes. This review paper aims to invoke the interest of industries to consider the merits of electrogenerative processes as a replacement for the current processes and practices. The applications of electrogenerative processes to the removal and recovery of metal ions, electrosynthesis of organic chemicals and leaching of sulfide minerals are discussed.
Fabrication of Pt/TiO2 Nanocomposites in Alginate and Their Applications to the Degradation of Phenol and Methylene Blue in Aqueous Solutions
Authors: Chen Peng , Zhang Xiaogang 
Published: June 2008

AbstractNew Pt‐containing titania composites have been produced by a conducting sol‐gel method within Pt/alginate hydrogels. The alginate gel was used as a template to prevent the conglomeration of the inorganic materials. During the calcination process, the Pt nanoparticles, which had been loaded in the alginate porous networks were transferred to the titania system, and formed the Pt/TiO2 composites. The amount of Pt embedded was studied from 0 to 0.74 mol.‐% (where mol.‐% refers to the Pt/TiO2 molar ratio), and the morphology and structure of the Pt/TiO2 composites were characterized by SEM, TEM, HAADF‐STEM, XPS, XRD, in addition to a study of the photocatalytic efficiency of these composites in aqueous methylene blue and phenol. Higher photocatalytic activity was observed at higher levels of Pt added to the titania system. The 0.37 mol.‐% sample was found to present the highest photocatalytic activity for the photodecomposition of aqueous methylene blue and phenol.
Enhancement of Methanol Tolerance in DMFC Cathode: Addition of Chloride Ions
Authors: Uhm Sunghyun , Noh Taegeun , Kim Yong Dok , Lee Jaeyoung 
Published: June 2008

AbstractIn the operation of a direct methanol fuel cell, the modification by chloride ions on the surface of a Pt cathode can facilitate the extraordinary increase of power performance and long‐term stability. Analyzing the results of cyclic voltammograms and electrochemical impedance spectroscopy, the positive shift of Pt oxidation onset potential and the depression of oxidation current are observed, which results from the role of chloride as surface inhibitor. In addition, O2 temperature‐programmed desorption and X‐ray photoelectron spectroscopy also reveal that the suppression of Pt surface oxide can be best understood in terms of lower binding of oxygen species by the alteration of electronic state of Pt atoms. Such a reduced surface oxide formation not only provides more efficient proton adsorption sites with high selectivity but also decreases the mixed potential by crossover methanol, resulting in higher performance and stability even under high voltage long‐term operation.
Fabrication of Stable Polyaniline Foams and Their Photoelectric Conversion Behaviors
Authors: Heng Liping , Wang Xinyi , Zhai Jin , Sun Zhongwei , Jiang Lei 
Published: June 2008

AbstractWe report a foaming‐polymerization method to prepare stable polyaniline (PANI)/polyvinyl alcohol (PVA) foams. The formation mechanism of the foam materials is investigated and the photoelectric conversion properties of PANI/PVA foams are studied in detail. The enhancement of photoelectric conversion behavior in foams is achieved, which has potential application in solar cells and nano‐electronics devices.