Премия имени А.А. Баландина 2001 года
Научный совет по катализу РАН -
Отчет о научно-организационной деятельности в 2001 году
За рубежом
Л.М. Кустов
Современные тенденции промышленного катализа
Дж. В. Ньемантсвердрит
Как готовить успешные устные и постерные презентации (часть 1)
The NATO Programme
The NATO Programme on Security-Related Civil Science and Technology announces three deadlines for receipt of applications - 1 February, 1 May and 1 October. Applications can be accepted for Advanced Research Workshops, Advanced Study Institutes, Collaborative Linkage Grants and Expert Visits. The Security-Related Civil Science and Technology area deals with (a) security of the environment in connection with all types of military activity; and (b) technologies for disarmament and conversion. It is aimed more at the application of the appropriate science and technology to the resolution of security-related problems, than at research per se. Topics include security-related biological science and technology (including biochemistry, biophysics, biotechnology, immunology, pharmacology, toxicology, epidemiology and related medical sciences); security-related nuclear science and technology; security-related chemical science and technology; security-related environmental science and technology; hazardous waste storage and disposal science and technology; conversion technologies; risk assessment; detection science and technology; weapons dismantlement technologies; and other security-related science and technology matters affecting both individuals and society.
Further information (and downloadable applications) on the support mechanisms described above can be found on the Internet at http://www.nato.int/science. Alternatively, application forms can be requested by: Tel: +32.2.707.4231; Fax: +32.2.707.4232; E-mail: science.fell@hq.nato.int
SUPRAMOLECULAR CLUSTER CATALYSIS
Conventional wisdom holds that in organometallic catalysis, substr
H-BOND DONORS AS ACID CATALYSTS
Hydrogen-bond donors such as thioureas that form multiple hydrogen bonds with carbonyl oxygen atoms in di-enophiles have been shown to make complexes that function in a fashion similar to traditional metal-containing Lewis acid catalyst adducts in Diels-Alder reactions [Org.Lett., published Jan. 4 ASAP, http://pubs.acs.org/journals/orlef7]. The results point to the potential use of H-bond additives as environmentally friendly replacements for Lewis acids in industrial processes, notes chemistry professor Peter R.Schreiner of the University of Georgia. Using NMR and IR spectroscopy and ab initio calculations, Schreiner and graduate student Alexander Wittkopp determined that complexation of thioureas with N-acyloxazolidinones is "well in line" with that of Lewis acids. In Diels-Alder additions of N-acyloxazolidinone to cyclopentadiene, the thioureas achieve near 75 % yield of the addition product at room temperature in 48 hours, in contrast to uncatalyzed reactions that require high temperature and give lower yields. Reactions with Lewis acids AlCl3 and TiCl4 achieve better than 90% yield in one hour at low temperature with slightly better diastereoselectivity.
C&EN/JANUARY 14, 2002
http://pubs.acs.org/CEN/
HYDROGEL OPALS
What is iridescent like a precious opal, yet soft, elastic, and water-swollen like gelatin? It's a hydrogel opal, a new type of bulk hydrogel that sparkles in many colors because of the way its crystalline structure diffracts light [Adv. Mater., 13, 1708 (2001)]. Polymer physicist Zhibing Hu and coworkers Xihua Lu and Jun Gao at the University of North Texas make the opals by first preparing nanoparticles consisting of N-isopropylacrylamide co-polymerized with acrylic acid or 2-hydroxyethyl acrylate. The nanoparticles are allowed to self-assemble in solutions, after which they are cross-linked to form a stable 3-D network. The resulting gels are as much as 97 % by weight water. The color and volume of the gels respond to changes in temperature and electric field. Temperature changes can make the gels become cloudy, obscuring their iridescence quickly and reversibly. The gel's fast response rate could be a major advantage over conventional colloidal crystal arrays for developing sensor or display technologies.
C&EN/November 19, 2001
http://pubs.acs.org/CEN/
TOMATOES WITH A TASTE FOR SALT
You'd hardly look to tomatoes for cutting-edge research news, but advances in genetic engineering have just turned the spotlight on that juicy red salad ingredient. Eduardo Blumwald, pomology professor at the University of California, Davis, and Hong-Xia Zhang, a postdoc in the botany department at the University of Toronto, report that genetically modified tomato plants flourish on a diet of 200-mM salt water and produce fruit that's healthy looking and tasty [Nat. Biotechnol., 19, 765 (2001)]. Extending this salt tolerance to other crops would be a boon to agriculture in vast regions of the world where farming is compromised by the adverse effects of salty irrigation water or salt-damaged soil. Typically, plants exposed to high salt concentrations dehydrate and die. But the genetically modified tomato plants manage to thrive on salt-water because the researchers engineered the plants to produce high levels of Na+/H+ antiport, a transport protein that provides plants with an ion-shuttling service. The protein directs sodium ions away from regions of plant cells where salt can interfere with metabolic functions and holds them in cellular storage compartments known as vacuoles.
C&EN/AUGUST 13, 2001
http://pubs.acs.org/CEN/
CRANKING UP THE TURNOVER NUMBER
High turnover numbers (TONs) have been observed during selective epoxidation of alkenes with molecular oxygen at one atmosphere catalyzed by a polyoxometalate [Angew. Chem. Int. Ed., 40, 3639 (2001)]. Using a di-iron-substituted silicotungstate, chemists Yoshiyuki Nishiyama, Yoshinao Nakagawa, and Noritaka Mizuno at the University of Tokyo find a TON of 10,000 for conversion of cyclooctene to cyclooctene oxide with 98 % selectivity over the alcohol and ketone co-products. That TON is 100 times higher that has previously been achieved with the same substrate and oxidant, the researchers note. Conversion of cyclododecene, 1-octene, 2-octene, 2-heptene, and 2-hexene proceed with TON's ranging from 1,300 to 9,600 with selectivity for the epoxide over the alcohol or ketone co-products. These encouraging results raise "the prospect of using this type of inorganic catalyst for industrial epoxidation processes", the researchers write. But for the reaction to be of practical use, the reaction times and the selectivities must be improved.
LOW-ENERGY ELECTRONS INDUCE SURFACE REACTIONS
Low-energy electrons can be used as selective probes to investigate structure, chemical bonding, and reactivity in thin films of hydrocarbons, according to a new study at the University of Southern California. Chemistry professor Bruce E. Koel and graduate student Denis Syomin find that beams of 30 eV electrons directed at metal surfaces covered with hydrocarbon layers induce C-H bond cleavage in a highly selective manner [Surf. Sci. Lett., 492, L693 (2001)]. The electron-induced dissociation process can be used to examine adsorbed layers of molecules or to modify the films chemically - for example, by covering the molecules to reactive intermediates or to stable products. Using a surface-sensitive IR spectroscopy technique and a mass spectrometry method that analyzes molecules desorbing from a specimen's surface, the researcher observes that under the influence of an electron beam, benzene that is weakly bonded to gold is converted to phenyl fragments. These species subsequently react with one another to form biphenyl. No other products are detected. Similarly, cyclohexane undergoes electron-induced bond cleavage, leaving a gold surface coated with reactive cyclohexyl fragments.
ACIDS, BASES AVOID MUTUAL DESTRUCTION
Chemists at Hebrew University of Jerusalem have managed to carry out sequences of acid- and base-catalyzed reactions in one pot by sequestering the acids and bases from one another [Angew. Chem. Int. Ed., 40, 3647 (2001)]. Chemistry professors David Avnir and Jochann Blum and graduate student Faina Gelman keep the acid and base from neutralizing one another by entrapping them in silica gel matrices. Acids are molybdic acid or a sulfonated perfluoro resin. Bases are N-2-aminoethylamino-propylated silica or 1,5,7-triazabicyclo[4.4.0]dec-5-ene. The chemists demonstrate their technique by heating benzene solutions of pinacol, malononitrile, and entrapped sulfonated resin and aminopropylated silica. In the sequence shown, the acid catalyzes rearrangement of pinacol to pinacolone, which undergoes base-catalyzed condensation with malononitrile to yield 83% overall of a 1,1-dicyano-1-butene.
C&EN/OCTOBER, 1 2001
http://pubs.acs.org/CEN/
FLUOROUS BIPHASIC TRANSESTERIFICATION
Catalyst-solvent system mediates quantitative 1:1 ester-alcohol reactions
A new fluorinated catalyst-solvent system that overcomes some of the traditional limitations of transesterification reactions - thus boosting its potential as a green industrial process - has been developed by a research team at Okayama University of Science in Japan.
Professor Junzo Otera, assistant professor Akihiro Orita, and coworkers in the department of applied chemistry report the 1:1 reaction of esters with alcohols using a fluorinated distannoxane catalyst in perfluorohexanes. The method leads to essentially 100 % conversion and yield of the desired esters [Angew. Chem. Int. Ed., 40, 3670 (2001)].
Generally, transesterification involved the acid- or base-catalyzed reaction of an ester and an alcohol that leads to double displacement of substituent groups. They are equilibrium-dependent reactions, meaning a large excess of the ester or alcohol is needed to drive the reaction, with one of the reactants usually acting as the solvent.
Otera and coworkers were looking for the "ultimate practical transesterification" that could satisfy some of the tenets of green chemistry. The goals included having a 1:1 ratio of ester and alcohol reactants (atom economy), a neutral catalyst that is readily recoverable, and 100% conversion and yield.
Earlier work of Otera's group on tetraalkyldistannoxanes led to the idea that such a catalyst with polyfluoroalkyl groups, when dissolved in a perfluorocarbon solvent, could lead to a useful fluorous biphasic reaction system. In this system, the catalyst and solvent form one layer, while the ester and alcohol reactants form a separate organic layer. On heating, the two layers are sufficiently miscible for the reaction to occur; on cooling, the organic and fluorinated layers separate.
The system was tested by carrying out a series of millimolar-scale reactions of methyl and ethyl esters with various high-boiling alcohols, including some acid-sensitive alcohols and protected alcohols. One representative reaction was ethyl-3-phenyl-propionate with 1-octanol at 150 oC for 16 h that gave greater than 99% yield of octyl-3-phenylpropionate. The pure ester was recovered by evaporation of the ethanol coproduct.
The catalyst can be recovered from the perfluorocarbon solvent, the researchers note, but it is more practical to reuse the solution directly in subsequent reactions. The viability of the fluorous phase was thus demonstrated by running a set of 14 different esterifications consecutively with the same catalyst-solvent sample, each of which proceeded in near 100 % conversion and yield. In a future paper, the Okayama group plans to explore how the 1:1 reactions proceed so efficiently. - Steve Ritter
C&EN/OCTOBER, 1 2001
http://pubs.acs.org/CEN/
Trimerization of acetylenes yields aromatic
t-Bu=tert-butyl, Pr=isipropil, Tol=p-tolyl
A trimerization of acetylene derivatives devised by biomolecular researchers at Tokyo Institute of Technology in Kanagawa yields a phenyltitanium reagent that reacts to give a variety of substituted benzenes (J. Am. Chem. Soc., 123, 7925 (2001)]. Their reaction could lead to synthesis of "druglike" combinatorial libraries based on four-component reactions. In one example, biomolecular engineering professor Fumie Sato, graduate student Daisuke Suzuki, and biological information professor Hirokazu Urabe mix tert-butyl 2-nonynoate,1-octyne, and η2-propylene-titanium(II) isopropoxide to get a titanofuran intermediate, which reacts with p-toluenesul-fonylacetylene to give a 3,5-dihexyl-2-carbo-tert-butoxy-phenyltitanium reagent. The phenyltitanium reacts with protons, iodine, or benzaldehyde to replace the titanium. Total overall yields are 46 to 88 %.
FTIR screens catalyst library
Fourier transform IR imaging can be used to analyze the reaction products from an entire array of catalysts at once, according to researchers at Purdue University's School of Chemical Engineering [Angew. Chem. Int. Ed., 46, 3028 (2001)]. They claim that the technique is the first truly parallel high-throughput screening method for monitoring gas-phase reaction products from combinatorial catalysts libraries. Associate professor Jochen Lauterbach, research fellow Chris M. Snively, and graduate student Gudbjorg Oskarsdottir have developed a gas-phase array attached to a multiple sample reactor that currently can investigate 16 supported catalysts simultaneously. They demonstrated the technique by analyzing the oxidation of propene over commercial and custom-synthesized samples of platinum-group metal catalysts, recording FTIR absorbance images every 30 seconds as they increased the temperature. The experiment showed seven catalysts oxidizing propene to CO2 at 440 K, while 12 catalysts were active at 650 K. The technique is capable of screening hundreds to thousands of catalyst samples on a timescale of seconds, they conclude.
