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Версия для печати | Главная > Центр > Научные советы > Научный совет по катализу > ... > 2006 год > № 38

№ 38

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СОДЕРЖАНИЕ

Поздравление
В.Б.Казанский (к 75-летию со дня рождения)

М.Г.Слинько
"Истоки и основы журнала "Катализ в промышленности"

Е.З.Голосман
"40 лет ИКАРУ "НИАП"

Е.З.Голосман
"Научный потенциал Тульского региона"

Т.В.Замулина, А.Н.Загоруйко, В.Я.Якововлев
"Химреактор-17"

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ВЛАДИМИР БОРИСОВИЧ КАЗАНСКИЙ (К 75-ЛЕТИЮ СО ДНЯ РОЖДЕНИЯ)

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ИСТОКИ И ОСНОВЫ ЖУРНАЛА "КАТАЛИЗ В ПРОМЫШЛЕННОСТИ"

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XVII Международная конференция по химическим реакторам ХИМРЕАКТОР-17

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Новости науки

Ultrafast electron microscopy

By integrating fast laser methods with transmission electron microscopy (TEM), researchers at Caltech have developed a microscopy technique that combines Angstrom spatial resolution with femtosecond time resolution (Proc. Natl. Acad. Sci. USA 2005, 102, 7069). The procedure, which was developed by Ahmed H. Zewail, Vladimir A. Lobastov and Ramesh Srinivasan, has been used to image various types of samples including gold crystals, amorphous carbon, and cells from rat intestines. Unlike conventional TEM, in which a hot cathode supplies electrons continuously via thermionic emission, in the Caltech method, electron emission is caused by illuminating the cathode with weak femtosecond laser pulses. Because it liberates very few electrons per pulse, the procedure sidesteps some of the difficulties that tend to broaden the electron beam and limit resolution. It also enables TEM images and videos to be recorded with unprecedented time resolution, thereby providing a route to atomic-scale dynamics studies of complex systems.

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С & EN / MAY 16, 2005

LG develops green route

structureLG Chem has developed a nonchlorine process for making the chemical intermediate terephthaldehyde. Current terephthaldehyde plants, which are mostly in China and India, use chlorine as a reactant and yield, the coproduct hydrochloric acid, LG says. It expects the new process to lower the price of terephthaldehyde by 50%: or more. The South Korean company plans to license the technology and start operating its own plant in 2008.

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С & EN /DECEMBER 5, 2005

Moving subsurface hydrogen atoms

Scientists at Pennsylvania State University have demonstrated a technique for imaging and manipulating hydrogen atoms just below the surface of a palladium crystal (Proc. Natl. Acad. Sci. USA 2005, 102,17907). Hydrogen interactions with precious metals are of key importance in hydrogen-storage applications, fuel cells, and other areas. In particular, subsurface H atoms have been fingered as intermediates in hydrogenation reactions on Pd, but until now the species has not been observed directly By treating a Pd crystal with hydrogen at elevated temperature and pressure, E. Charles H. Sykes, Paul S. Weiss, and coworkers prepare samples in which a small amount of H atoms are absorbed into the crystal’s bulk. .Then, by applying voltage pulses to select positions on the crystal surface with a scanning tunneling microscope tip, the team induces the atoms to accumulate at stable sites just below the top Pd layer, where they can form patterns of lines measuring just a few nanometers wide, as shown.

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С & EN / DECEMBER 12, 2005

Microwaves do enhance reaction rates

Microwave ovens have become popular tools to facilitate chemical reactions, but it has been unclear if the observed enhanced reaction rates result from rapid heating or from interactions of microwaves with the bonds of the reactants. Chemical engineer Roshan Jachuck of Clarkson University, Potsdam, N.Y., and his coworkers have now shown that microwave radiation indeed has a significant impact on reaction rates (Green Chem. 2006, 8, 29). Jachuck’s group designed and built a continuous capillary microreactor that can be maintained at a constant temperature while being irradiated with microwaves. The researchers used the reactor to study the iron-catalyzed conversion of benzyl alcohol to benzaldehyde. The reactor produced benzalde hyde in about 75% yield under optimized conditions, which equated to a reaction time of about 15 seconds and a flow rate of about 1 mL/minute. The key observation was that increasing the microwave intensity at constant temperature increased die yield of benzaldehyde. Jachuck envisions that frequency-tunable microwave microreactors could be used for lab- or pilot-scale projects or for production of low-volume active pharmaceutical ingredients.

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С & EN / JANUARY 30, 2006

Enzyme activity: Out with the old, in with the new

Mimicking the natural process of evolution, researchers have redesigned a natural enzyme, thereby causing it to lose its original activity and adopt a new one (Science 2006, 311, 535). Hak-Sung Kim of the Korea Advanced Institute of Science & Technology, Daejon, South Korea, and coworkers started with a core structure of the enzyme glyoxalase II that has thiolester hydrolysis activity. They subjected the protein to an approach called SIAFE (simultaneous incorporation and adjustment of functional elements) in conjunction with directed evolution (iterative modification and selection for desirable activity). The result was evMBL8, a designed enzyme with the ability to hydrolyze (b -lactam amide bonds, a type of activity on which bacterial resistance to (b-lactam antibiotics is based. Key to the change was the replacement of several of the enzyme’s surface loop structures. The researchers say they hope the technique can be extended to convert other structures into enzymes that catalyze diverse reactions, including some not found in nature.

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С & EN / JANUARY 30, 2006

Double C-F/C-H bond activation

structureSuperstrong C-F bonds don’t readily lend themselves to activation and subsequent reaction, but that hasn’t stopped chemists from edging closer to a general method for C-F activation. In one of the latest efforts, Kohei Fuchibe and Takahiko Akiyama of Gakushuin University, in Tokyo, report a "double activation" reaction in which a C-F bond and a C-H bond in close proximity in the same molecule are jointly activated, leading to ring-closing and formation of a new molecule (J. Am. Chem. Soc. 2006,128, 1434). The researchers reacted o-phenyl-a,a,a -trifluorotoluene with NbCl5 and LiAlH4 to form fluorene in up to 82% yield (shown). They also synthesized a series of substituted fluorenes from various substituted phenyltrifluorotoluenes. "This is a pretty cool reaction," notes Oleg V. Ozerov of Brandeis University, Waltham , Mass., who also works on C-F activation chemistry. "This chemistry goes beyond what anyone else has been able to accomplish in that C-F activation is coupled with C-H activation in a C-C bond-forming step," he says. The substituted fluorenes are potential core structures for pharmaceuticals and for polymers used in molecular electronics.

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С & EN / JANUARY 30, 2006


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