Файл: М.М. Герасимцева Тексты для аудиторного и внеаудиторного чтения (Английский язык).pdf

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FULLERENES

This somewhat puzzling term stands for a special crystalline form of carbon. This chemical element - the basic component of all organic life on our planet – seems to have been investigated down to the finest details in two of its best-known forms – diamond and graphite – which differ by their physical and chemical properties. In the former atoms are "packed" in the form of spatial tetra-hedrons, and in the latter – in hexagonal and rhombohedral laminated structures.

Over the past few decades, however, scientists came to question the finality of these two forms of carbon; some suggested the existence of other spatial chemically stable structures of carbon atoms. Speaking in metric terms, one such structure could be an icosahedron whose geometry was originally described by Archimedes. This structure is a hollow spatial configuration which can be compared to a football with a multitude of pentahedral and hexahedral sides, or

facets. Its molecule should have the chemical formula of C6O. And after a long search astrophysicists finally traced in the mass spectra of carbon vapor a characteristic peak which suggested the existence of a matching molecule.

These, however, were but purely theoretical assumptions which could not be confirmed by any practical findings, here on Earth. And it was only in 1985 that a team of American researchers, investigating carbon by what is called the atomic cluster method using laser evaporation, identified for the first time ever as C6O molecule with the help of time-of-flight mass-spectrometer. What is more, in subsequent experiments not only C6O, but also C7O could be identified.

More detailed studies of the new substance suggested the existence of a carbon molecule in the form of a closed hexagonal cell, or cage. The latter reminded the investigators of a geodesic dome with 60 apexesa structure brainstormed by the US inventor and architect Richard Buckminster Fuller

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which was translated into building construction reality at the EXPO-67 in Montreal. This similarity suggested the name for the new molecule which was called – buckminsterfullerene - a mouthfull which was later reduced to just fullerene. However, the unit which helped trace C6O molecules for the first time could be used for analytical studies only, and not for any quantitative isolation of the substance in question.

This problem was finally solved in 1990 by the German scientist W. Kretschmer who not only developed an appropriate unit, but also designed a technology for obtaining sample amounts of fullerene. He demonstrated for the first time that using arc discharges with graphite electrodes and helium (as buffer gas), one can obtain carbon condensate containing C6O molecules. That marked the start of what we call fullerene technologies. Within a short span of time researchers were able to discover what were called lower, or base fullerenes (up to 22 atoms) and higher ones (up to 270 atoms), all of them possessing a range of specific properties. Because of all that they were regarded not just a new and challenging object of basic research, but also as the basis for a range of promising applied innovations.

Studies of this amazing phenomenon led the researchers to the conclusion that it can be used in some very different areas of science and technology, above all in electronics and optoelectronics, organic chemistry and metallurgy and in the manufacture of tyres and jewellery, to name but a few. And the range of the newly discovered and unique properties of fullerenes continues to grow just as does the scale of their applications.

With all that, there is but one snag in using this material on a really broad scale, and this is the cost. In 1994, for example, the price of pure C6O fullerene on the world market was 550 US dollars for one gram, and it was 1,600 dollars for C7O.

Studies of fullerenes at the Physics Institute (named after L. Kirensky) of the Siberian Branch of the Russian Academy of Sciences (Krasnoyarsk) were initiated in 1992. Dr. G. Churilov, a specialist in plasmotrons, or plasma generators*, offered to his colleagues-physicists his own experimental unit for the production of this material. It took them two years to make the necessary adjustments before they were finally able to isolate the material from a carbonic jet in the plasma generator. All of these efforts finally led to the development of a very simple and productive, while likewise unique, technology of synthesis of this variety of carbon. The new area of research focused on fullerenes found a

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most fitting "niche" in the Federal Program of INTEGRATION adopted in this country in 1995. Within the frame-work of this program a PhysicoTechnological Research Institute was set up with a special chair of plasmochemical technologies. And this form of carbon has since caught the attention of scientists in various fields of research. Chemists, for example, focused on ways of obtaining fullerene solutions and their purification, while physicists have been trying to identify this unique substance with the help of electron spectroscopy in the visible, ultraviolet and infrared bands, while medical experts try using them as biological solutions and biophysicists take special interest in their water-soluble complexes.

The latter studies provided an incentive for research in a promising area linked with practical uses of the new material in biology and medicine. The point is that fullerenes, having a definite number of non-saturated bonds, are unique objects capable of gaining electrons, and are also ideal components for reactions with free radicals. This makes it possible to use them as "traps" (antioxidants) in the hyperproduction of active forms of oxygen - the predominant mechanism of body ageing and pathologies. Specialists are now studying the effect of various water-soluble complexes, containing both higher and lower fullerenes, upon oxygen metabolism in the blood of patients with different pathologies. It has been demonstrated that higher fullerenes are hyperactive and have a strong effect on redox processes in organic compounds. This is very important, for it thus becomes possible to develop new anti-cancer and anti-viral medicines.

The results obtained point to a very promising nature of the current studies of fullerenes. For example, a method developed by Dr. G. Churilov, using an HF plasma jet in the range of up to 0.75 m, makes it possible to design various fullerene complexes at the molecular level. These complexes (obtained by introducing various fractions of other substances or combinations thereof into a C6O molecule) may reveal some very unexpected and useful properties. If, let us say, an excited hydrogen atom is implanted into a fullerene structure and fixed therein, the resulting substance can become what we call an absolute absorbent of electromagnetic emissions, so that any object coated with a paint of this kind will become absolutely invisible to radars. Apart from the above, a "sustained" source of plasmochemical synthesis should make it possible to boost the production of fullerenes and cut back their cost.

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The problem of synthesis of such minute particles is drawing considerable attention and interest on the part of specialists, including theoreticians, experimenters and practical, or applied researchers. This area of research is in the list of what we call critical national technologies, which proves how important and promising it is. At Krasnoyarsk this line of research began with studies of ultra-dispersed diamond powders and has since branched out into many fields, including studies of nanostructures of various materials and some theoretical and practical problems of nuclear engineering.

* Plasmotron (plasma generator) – gas discharge unit for generating lowtemperature plasma (T104 K).

4. Say in English:

Исследовать до мельчайших деталей, пространственные химически устойчивые структуры, чисто теоретические предположения, атомный пучковый метод, последующие эксперименты, обсуждаемое вещество, короткий промежуток времени, обладать рядом особых свойств, спорный объект исследований, экспериментальная установка, видимый спектр, водорастворимые комплексы, ненасыщенные связи, кислородный метаболизм, противораковые и противовирусные медикаменты, неожиданные свойства.

5. Answer the following questions:

What forms of carbon do you know?

Who identified C6O molecule for the first time? When was C6O molecule identified?

In what areas of science and technology can fullerenes be used?

Where was a very simple and productive technology of synthesis of fullerenes developed?

Why can higher fullerenes be used in development of new medicines? What useful properties do fullerene complexes reveal?

What can cut back the cost of the production of fullerenes?

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TEXT 4

Pre-reading tasks:

1. Read the words and try to memorize their pronunciation:

Pyroxene, authenticity, discredit, meteorite, kalininite, nataliite, feorensovite, rare, chromphillite, mica.

2. Words and phrases to be learnt:

3. Guess the meaning of the following words:

mineral, pyroxene, chemist, vanadium, zinc, chromium, museum, group, mineralogical.

DISCOVER YOUR MINERAL

Some 150 years ago Russian mineralogist, Member of. the St. Petersburg Academy of Sciences, Nikolai Koksharov, made an interesting discovery while visiting a small village, Slyudyanka, on the shore of Lake Baikal in Siberia. What he found was a mineral of an unusual salad color which belonged to the pyroxene group. He named his find "lavrovite" in honor of the then President of the All-Russia Imperial Society of Mineralogy Lavrov. 20 years later the find was studied for the first time by a team of German chemists. During more than one hundred years since Koksharov's discovery none of the mineralogists who studied the mineral has confirmed the "vanadium-related" color of lavrovite, although the fact that it contains vanadium was common knowledge among experts. Quite recently a team of German chemists have published an article under an intriguing title questioning the "authenticity" of lavrovite. This was followed by a report on a discredit of the very name "lavrovite".

The controversy has attracted the attention of Dr. Leonid Reznitsky, a research scientist of the Institute of the Earth Crust of the Siberian Branch of the Russian Academy of Sciences (Irkutsk). He and his team visited the site of the original discovery – the village of Slyudyanka in Siberia. What they found there was not only the mineral in question, but five new ones as well.

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The first of these turned out to be a very unusual one: it belonged to the spinel group which contains zink, chromium and sulphur – a very rare group earlier encountered only in meteorites. The mineral was given the name of "kalininite" in honor of a scholar who studied the Pribaikalye (near Baikal) region - Professor Pyotr Kalinin of the Moscow Institute of Geological Prospecting.

The second mineral in the group – and contrary to the claims of the German scientists - was vanadium pyroxene. Dr. Reznitsky called it "nataliite" after a prominent Siberian geologist Dr. Natalya Frolova.

The third of the newly discovered mineral also features an unusual composition – some of its chromium is replaced with) antimony (such compound was found for the first time). It was given the name of "florensovite" in honor of Nikolai Florensov the founder of the Institute of the Earth Crust of the Siberian Branch of the Russian Academy of Sciences, Corresponding Member of the Academy.

The fourth and fifth of the newly discovered minerals can be described as varieties of vanadium spinel and rare chromium mica. The latter is an analog of muscovite mica in which aluminum is replaced with chromium that gives the mineral its beautiful bright-emerald color. And it was called "chromphillite".

Dr. Reznitsky's fellow partner in nearly all of the discoveries is Corresponding Member of the Russian Academy Yevgeny Sklyarov – Director of the Institute of the Earth Crust of the Siberian Branch of the Russian Academy.

Over the past few decades the Institute's scientists have discovered more than 20 new minerals. In addition to those mentioned above, seven were discovered by a leading researcher of the same Institute Alexander Konev, another five (including charoite – a fine stone of a violet color) by Vera Rogova, and still another seven by researchers from the Vinogradov Institute of Geo-chemistry -Vladimir Ivanov, Yevgeny Vorobyev and Nikolai Vladykin. And the search continues now, adding to Slyudyanka's unique record of more than 200 years as a "natural" mineralogical museum.

5. Answer the following questions:

Where did the interesting discovery of minerals take place? What minerals does the spinel group contain?

What does “Lavrovite” mean?

Who discovered more than 20 new minerals?

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Where did discovery of the rare chromium take place?

Nikolai Florensov – what is he?

What minerals belong to the pyroxene group?

4. Say in English:

пироксеновая группа, ванадиевая шпинель, состав минерала, редкая хромовая слюда, яркий изумрудный цвет, институт по исследованию земной коры, минералогический музей.

TEXT 5

Pre-reading tasks:

1. Read the words and try to memorize their pronunciation:

Ketone, application, heterocyclic, tautomerism, cis-tran-isomerism, aminodienone, aminopolyenone, aminovinyl, comprehensively, accessible, conjugate.

2. Words and phrases to be learnt: conjugate - сочленять

heterocyclic - многоцикличный reactivity - реактивность

3. Guess the meanings of the following words:

Electron-donor, electron-acceptor, fundamental, tautomerism, cis-trans- isomerism, monograph, traditional, chemical transformation, methyl group, polyene, carbonyl, ω-amino, aminopolyenones, aminovinyl, diketones, isoxazoles, nitriles, alkoxy.

METHODS FOR THE SYNTHESIS OF CONJUGATED

ω-AMINO KETONES

Conjugated ω-amino ketones represent a vast class of organic compounds, which draw attention of researchers engaged in various fields. Owing to their high reactivity, these compounds find application in the synthesis of various biologically active heterocyclic systems, natural products, dyes and lightsensitive materials. The presence in ω-amino ketones of electron-donor and

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electron-acceptor groups separated by conjugated double bonds makes them convenient models for investigations into fundamental theoretical problems such as the nature of chemical bond, excitation, transfer of electrons along the chain of conjugation, colour, sensitivity to various types of external treatment, tautomerism, cis-trans-isomerism, etc.

This review surveys the data on the synthesis of β-enamino ketones, δ-aminodienones and conjugated ω-aminopolyenones of various structures.

Methods for the synthesis of β-aminovinyl ketones have been studied fairly comprehensively; they were discussed in reviews and in a monograph published in the 70s and 80s. In recent years, traditional methods for the synthesis of β-aminovinyl ketones have been modified to increase the yields of the target products and to simplify the experimental procedures. The methods of regioand stereospecific synthesis - of enamino ketones containing additional functional groups are being rapidly developed now. The review covers those methods which either are very convenient and readily accessible or involve unusual chemical transformations such as reactions of β-diketones with ammonia or amines, reactions of unsaturated alkoxy ketones with amines, reductive cleavage of isoxazoles, condensation of acid nitrites with methyl ketones, modification of β-aminovinyl ketones with the use of their lithium salts, and reactions with amideor lactam acetals with compounds containing an active methyl group or a methylene unit.

As a rule, the conventional methods cannot be used to synthesise conjugated δ-aminodienones and, especially, polyene ω-amino ketones containing more than two conjugated double bonds between the NMe2 and CO groups. Several specific methods are described for this purpose.

Data on the structures and properties of the compounds synthesised are given.

Considerable attention is paid to conjugated ω-aminopolyenones. Methods for the synthesis of these compounds have been developed only recently. A specific type of these compounds is represented by α,α'-bis(ω-aminopolyenyl) ketones containing two polymethyl chains linked by a carbonyl group. These compounds exhibit unusual spectral - luminescence properties.