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Translate from English into Russian.



Chemical bond __________________ Electron affinity __________________
Properties ______________________ Saturated hydrocarbons ____________
Breakdown _____________________ Continuous phase _________________
Decomposition reaction ___________ Catalyst _________________________
Precipitation ____________________ Investigator ______________________
Redox reaction __________________ True solution _____________________
Acid-base titration _______________ Equilibrium constant _______________
Flask __________________________ Quantitative analysis _______________
Calibration curve ________________ Bond strength ____________________
Carbohydrates __________________ Elimination reaction _______________

_______ Max 20

Match A and B.

A B
1. This group being inert to most __________, it is impossible to hydrolyze it. a) separate
2. Titanium seems to combine all the best __________ of steel and aluminium with other valuable ones of its own. b) investigation
3. To __________ the thorium from iron, this precipitate is dissolved in hydrochloric acid. c) catalysts
4. Copper and gold oxides are weak bases, the basic character decreasing as the __________ rises. d) reagents
5. Three products are likely to be formed by the electrolytic __________ at a lead cathode e) atomic weight
6. If we prepare some HgCd alloys and allow the alloy to reach the ordinary __________, it will generally solidify if enough Cd is present. f) liquid
7. Having examined it carefully, we found out that the gas under _________ exhibited anomalous behavior. g) acid
8. __________ accelerate the reactions that otherwise would be too slow. h) temperature
9. The acidity of solutions is often expressed in terms of pH; the lower the pH, the more _____ in the solution. i) properties
10. The residue left after most of the __________ air had boiled away consisted of oxygen and nitrogen. j) reduction

_______ Max 20

Fill in the gaps.

1. Carbon is the main common __________ in organic chemistry.

2. The catalyst is the most effective at 840 __________ Celsius.

3. The acid __________ must be about 98% at the final stage.

4. Titration is a technique used to determine amounts present in solution or a physical characteristic of a molecule such as an __________ constant.

5. The color changes when the universal __________ is used.

6. __________ is the scientific study of matter in its various forms that contain carbon atoms.

7. Alcohols are molecules containing the __________ functional group (-OH) that is bonded to carbon atom of an alkyl.

8. Aerosol contains small particles of liquid or solid dispersed in a _________.

9. A colloid is a _________ that has particles ranging between 1 and 1000 nanometers in diameter.

10. Chemical kinetics shows how the _________ of reactions respond to changes in conditions or the presence of a catalyst.

_______ Max 20

Make up sentences using the words.

With, Coordination, complexes, the, of, chemistry, deals, study.

2. acidic, A, substance, be, basic, chemical, can, or.

3. of, studied, both, under, Phenomenon, and, chemistry, radioactivity, inorganic, is, physical.

4. are, methods, Where, analytical, applied?

5. Carbon dioxide, plant very, to, processes, is, necessary, for, chemical, life, important.

Of, studied, both, under, Phenomenon, and, chemistry, radioactivity, inorganic, is, physical.

Double, also, metathesis, reactions, displacement, may, be, reactions, called.

8. methods, do, rely, analytical, What, on?

9. Is, the solution, known, The standard,of, concentration, solution.

10. I’m, know, sure, between, you, solid, and, a, gas, the, a, difference!

_______ Max 20

Translate into English.

1. Вещества, в которых гидроксильная группа связана с ароматическим кольцом, называются фенолами.

2. Белки — это макромолекулы, состоящие из одной или нескольких цепей аминокислотных остатков.

В некоторых случаях коллоид может рассматриваться как гомогенная смесь.



4. Химическая реакция происходит, когда атомы взаимодействуют друг с другом и образуют новые комбинации.

5. Водород — самый легкий химический элемент.

6. Существуют соединения, имеющие одинаковый состав, но разную структуру.

Во время титрования титрант прибавляют к раствору неизвестной концентрации для достижения точки эквивалентности.

Стандартный раствор — это раствор известной концентрации.

9. Органические вещества классифицируют в соответствии с функциональными группами, например, спирты, альдегиды, углеводы, амины и т. д.

10. Химия – это наука, которая изучает вещества и их превращения.

_______ Max 20

TRANSLATION PRACTICE

TEXT 1

CHEMISTRY AROUND US

Chemical reactions influence the stuff around us and there are numerous instances where chemicals and chemistry helps us live a better life. The cooking of food, the clothes we wear, fertilizers that we use for crops, cement used for building our houses, the power plants that generate electricity, and many other processes depend on chemistry. The human dependence on this natural science is increasing and to understand this, here are a few examples that highlight the importance of chemistry around us.

1. Photosynthesis. Photosynthesis involves energy transformation and is a chemical process wherein plants, algae and some bacteria produce their own food. It is the synthesis of glucose using carbon dioxide and water in presence of sunlight trapped by chlorophyll present in the leaves. The reaction which occurs is depicted as: 6CO2 + 6H2O + Light Energy = C6H12O6 + 6O2. Photosynthesis is the reverse process of respiration. They both are inter-dependent. We get an uninterrupted supply of oxygen, and plants get the carbon dioxide they need. Thus, photosynthesis plays a significant role in our day-to-day life.

2. Color of Meat. There are two types of meat: red and white. Red meat contains a highly pigmented protein called myoglobin that stores oxygen in the muscle cells. More the myoglobin in the cells, the redder is the meat. However, as meat is heated, the proteins break down and shrink in size. When the interior of the meat reaches 170° F, hemichrome (a tan colored compound) levels rise, and the myoglobin becomes metmyoglobin, which gives well-done meat its brown-gray shade. White meat contains glycogen, which has a translucent "glassy" quality when it is raw. When it's cooked, the proteins recombine, or coagulate, and the meat becomes opaque and whitish.

3. Apples Turning Brown. Apples contain an enzyme called polyphenol oxidase (PPO), also known as tyrosinase. Cutting an apple exposes its cells to the atmospheric oxygen and oxidizes the phenolic compounds present in apples. This is called the enzymatic browning that turns a cut apple brown. In addition to apples, enzymatic browning is also evident in bananas, pears, avocados and even potatoes.



4. Crying and Onions. When you cut an onion you break the cells that form the layers in an onion, thus releasing an enzyme alliinase that reacts with a sulfur-containing compound known as 'prensco', which is also released while cutting. This reaction results in the formation of 1-propenyl sulfenic acid. This acid is further converted to propanethiol S-oxide, a volatile sulfur compound, by the enzyme LF-synthase (meaning lachrymatory factor synthesizing enzyme). This gas, known as the lachrymatory factor (crying factor), reacts with the water in our eyes to form sulfuric acid causing a burning sensation in your eyes and indicating the tear gland to secrete tears.

5. Stain Removers. Soap is formed by the reaction between an alkali and a fatty acid. This produces a molecule with one hydrophilic (water-loving) and one lipophilic (fat-loving) ends. The lipophilic ends stick to oil, grease or dirt. These get engulfed in the soap and are washed away with a fresh stream of water, leaving a clean surface behind. This is just a physical reaction that takes place. Soap and stain removers act as emulsifiers which allow oil and water to mix and so the oily mixtures and difficult stains on body and clothes can be removed after application of soap, stain removers and water.

6. Ripening of Fruits. A simple hydrocarbon gas ethylene switches on the necessary genes that stimulate the secretion of the ripening enzymes which catalyze reactions to change the properties of the fruit. Ethylene channelizes the action of several other chemicals called hydrolase, amylase, kinase and pectinase. These enzymes convert starch to sugar, alter the cell walls to make them softer, neutralize acids and cause the fruit to emit an aroma.
7. Fermentation. Fermentation is the conversion of complex substances to simpler ones under anaerobic conditions. The specific product from fermentation is driven by the type of micro-organisms acting on the substance in which the fermentation occurs. The products of fermentation are alcohols or acids and the release of carbon dioxide. For example, wine produced from fruit juice is an alcohol as a result of fermentation by yeast, whereas beer is the result of yeast fermentation of grain. Antibiotics are obtained through fermentation by molds and some bacteria. Yogurt, cheese and vinegar are products of bacterial fermentation. Leavened bread is obtained by yeast fermentation.

8. Sunscreens. Sunscreens are a combination of organic and inorganic compounds. Inorganic chemicals like titanium dioxide or zinc oxide form a physical barrier that reflects or scatters UV waves. Organic components like octyl methoxycinnamate (OMC) or oxybenzone absorb UV rays and release their energy as heat. This protects our skin from sunburns and detrimental effects like cancer.

9. Nail Paint Removers. Nail paint consists of three types of ingredients which are organic solvents and drying agents, thickeners and hardening agents along with coloring agents. The remover is actually an organic solvent that is used as an ingredient in nail paint which may be acetone or ethyl acetate. So when you apply the remover you are just bringing it back to its original state. The solvent molecules get in between the chains of polymers and separate them, making it easy to wipe it off with a ball of cotton.

10. Static Shocks. All materials are made up of electrical charges in the atoms of the material. There are equal quantities of electrons (negative charges) and protons (positive charges) that try to balance each other in the universe. Friction between two materials causes these charges to redistribute. The electrons from one atom are transferred to the other. As we know, like charges repel each other and unlike charges attract each other. Whenever you touch anything that is a good conductor of electricity, the transfer of the extra electrons that have accumulated takes place, and it gives you the static shock. For example, generally in winters, you get a shock when you get out of the car or when you touch the door knob or filing cabinet.

 

TEXT 2

ENZYMES

Enzymes are macromolecular biological catalysts. They are responsible for thousands of metabolic processes that sustain life. Enzymes are highly selective catalysts, greatly accelerating both the rate and specificity of metabolic chemical reactions, from the digestion of food to the synthesis of DNA. Most enzymes are proteins, although some catalytic RNA molecules have been identified. Enzymes adopt a specific three-dimensional structure, and may employ organic (e.g. biotin) and inorganic (e.g. magnesium ion) cofactors to assist in catalysis.

Enzymes act by converting starting molecules (substrates) into different molecules (products). Almost all chemical reactions in a biological cell need enzymes in order to occur at rates sufficient for life. Since enzymes are selective for their substrates and speed up only a few reactions from among many possibilities, the set of enzymes made in a cell determines which metabolic pathways occur in that cell, tissue and organ. Organelles are also differentially enriched in sets of enzymes to compartmentalize function within the cell.

Like all catalysts, enzymes increase the rate of a reaction by lowering its activation energy (Ea). As a result, products are formed faster and reactions reach their equilibrium state more rapidly. Most enzyme reaction rates are millions of times faster than those of comparable un-catalyzed reactions and some are so fast that they are diffusion limited. As with all catalysts, enzymes are not consumed by the reactions they catalyze, nor do they alter the equilibrium of these reactions. However, enzymes do differ from most other catalysts in that they are highly specific for their substrates. Enzymes are known to catalyze about 4,000 biochemical reactions. A few RNA molecules called ribozymes also catalyze reactions, with an important example being some parts of the ribosome. Synthetic molecules called artificial enzymes also display enzyme-like catalysis.

Enzyme activity can be affected by other molecules: decreased by inhibitors or increased by activators. Many drugs and poisons are enzyme inhibitors. Activity is also affected by temperature, pressure, chemical environment (e.g., pH), and the concentration of substrate. Some enzymes are used commercially, for example, in the synthesis of antibiotics. In addition, some household products use enzymes to speed up biochemical reactions (e.g., enzymes in biological washing powders break down protein or fat stains on clothes; enzymes in meat tenderizers break down proteins into smaller molecules, making the meat easier to chew). The study of enzymes is called enzymology.

The term enzyme comes from zymosis, the Greek word for fermentation, a process accomplished by yeast cells and long known to the brewing industry, which occupied the attention of many 19th-century chemists.

Louis Pasteur recognized in 1860 that enzymes were essential to fermentation but assumed that their catalytic action was inextricably linked with the structure and life of the yeast cell. Not until 1897 was it shown by German chemist Edward Büchner that cell-free extracts of yeast could ferment sugars to alcohol and carbon dioxide; Büchner denoted his preparation zymase. This important achievement was the first indication that enzymes could function independently of the cell.

The first enzyme molecule to be isolated in pure crystalline form was urease, prepared from the jack bean in 1926 by American biochemist J. B. Sumner, who suggested, contrary to prevailing opinion, that the molecule was a protein. In the period from 1930 to 1936, pepsin, chymotrypsin, and trypsin were successfully crystallized; it was confirmed that the crystals were protein, and the protein nature of enzymes was thereby firmly established.

 

TEXT 3

VITAMINS

A vitamin is an organic compound and a vital nutrient that an organism requires in limited amounts. An organic chemical compound (or related set of compounds) is called a vitamin when the organism cannot synthesize the compound in sufficient quantities, and must be obtained through the diet; thus, the term "vitamin" is conditional upon the circumstances and the particular organism. For example, ascorbic acid (vitamin C) is a vitamin for humans, but not for most other animal organisms. Supplementation is important for the treatment of certain health problems, but there is little evidence of nutritional benefit when used by otherwise healthy people.

By convention, the term vitamin includes neither other essential nutrients, such as dietary minerals, essential fatty acids, or essential amino acids (which are needed in greater amounts than vitamins) nor the great number of other nutrients that promote health, and are required less often to maintain the health of the organism. Thirteen vitamins are universally recognized at present. Vitamins are classified by their biological and chemical activity, not their structure. Thus, each "vitamin" refers to a number of vitamer compounds that all show the biological activity associated with a particular vitamin. Such a set of chemicals is grouped under an alphabetized vitamin "generic descriptor" title, such as "vitamin A", which includes the compounds retinal, retinol, and four known carotenoids. Vitamers by definition are convertible to the active form of the vitamin in the body, and are sometimes inter-convertible to one another, as well.

Vitamins have diverse biochemical functions. Some, such as vitamin D, have hormone-like functions as regulators of mineral metabolism, or regulators of cell and tissue growth and differentiation (such as some forms of vitamin A). Others function as antioxidants (e.g., vitamin E and sometimes vitamin C). The largest number of vitamins, the B complex vitamins, function as precursors for enzyme cofactors that help enzymes in their work as catalysts in metabolism. In this role, vitamins may be tightly bound to enzymes as part of prosthetic groups: For example, biotin is part of enzymes involved in making fatty acids. They may also be less tightly bound to enzyme catalysts as coenzymes, detachable molecules that function to carry chemical groups or electrons between molecules. For example, folic acid may carry methyl, formyl, and methylene groups in the cell. Although these roles in assisting enzyme-substrate reactions are vitamins' best-known function, the other vitamin functions are equally important.

Until the mid-1930s, when the first commercial yeast-extract vitamin B complex and semi-synthetic vitamin C supplement tablets were sold, vitamins were obtained solely through food intake, and changes in diet (which, for example, could occur during a particular growing season) usually greatly altered the types and amounts of vitamins ingested. However, vitamins have been produced as commodity chemicals and made widely available as inexpensive semisynthetic and synthetic-source multivitamin dietary and food supplements and additives, since the middle of the 20th century.

Vitamins are classified as either water-soluble or fat-soluble. In humans there are 13 vitamins: 4 fat-soluble (A, D, E, and K) and 9 water-soluble (8 B vitamins and vitamin C). Water-soluble vitamins dissolve easily in water and, in general, are readily excreted from the body, to the degree that urinary output is a strong predictor of vitamin consumption. Because they are not as readily stored, more consistent intake is important. Many types of water-soluble vitamins are synthesized by bacteria. Fat-soluble vitamins are absorbed through the intestinal tract with the help of lipids (fats). Because they are more likely to accumulate in the body, they are more likely to lead to hypervitaminosis than are water-soluble vitamins. Fat-soluble vitamin regulation is of particular significance in cystic fibrosis.

The term vitamin was derived from "vitamine," a compound word coined in 1912 by the Polish biochemist Kazimierz Funk when working at the Lister Institute of Preventive Medicine. The name is from vital and amine, meaning amine of life, because it was suggested in 1912 that the organic micronutrient food factors that prevent beriberi and perhaps other similar dietary-deficiency diseases might be chemical amines. This was true of thiamine, but after it was found that other such micronutrients were not amines the word was shortened to vitamin in English.

 

 

TEXT 4

MICELLE

A micelle or micella (plural micelles or micellae, respectively) is an aggregate of surfactant molecules dispersed in a liquid colloid. A typical micelle in aqueous solution forms an aggregate with the hydrophilic "head" regions in contact with surrounding solvent, sequestering the hydrophobic single-tail regions in the micelle centre. This phase is caused by the packing behavior of single-tail lipids in a bilayer. The difficulty filling all the volume of the interior of a bilayer, while accommodating the area per head group forced on the molecule by the hydration of the lipid head group, leads to the formation of the micelle. This type of micelle is known as a normal-phase micelle (oil-in-water micelle). Inverse micelles have the head groups at the centre with the tails extending out (water-in-oil micelle). Micelles are approximately spherical in shape. Other phases, including shapes such as ellipsoids, cylinders, and bilayers, are also possible. The shape and size of a micelle are a function of the molecular geometry of its surfactant molecules and solution conditions such as surfactant concentration, temperature, pH, and ionic strength. The process of forming micelles is known as micellisation and forms part of the phase behaviour of many lipids according to their polymorphism.

The ability of a soapy solution to act as a detergent has been recognized for centuries. However, it is only at the beginning of the twentieth century that the constitution of such solutions was scientifically studied. Pioneering work in this area was carried out by James William McBain at the University of Bristol. As early as 1913, he postulated the existence of “colloidal ions” to explain the good electrolytic conductivity of sodium palmitate solutions. These highly mobile, spontaneously formed clusters came to be called micelles, a term borrowed from biology and popularized by G.S. Hartley in his classic book Paraffin Chain Salts: A Study in Micelle Formation.

Individual surfactant molecules that are in the system but are not part of a micelle are called "monomers". Lipid micelles represent a molecular assembly, in which the individual components are thermodynamically in equilibrium with monomers of the same species in the surrounding medium. In water, the hydrophilic "heads" of surfactant molecules are always in contact with the solvent, regardless of whether the surfactants exist as monomers or as part of a micelle. However, the lipophilic "tails" of surfactant molecules have less contact with water when they are part of a micelle—this being the basis for the energetic drive for micelle formation. In a micelle, the hydrophobic tails of several surfactant molecules assemble into an oil-like core, the most stable form of which having no contact with water. By contrast, surfactant monomers are surrounded by water molecules that create a "cage" of molecules connected by hydrogen bonds. This water cage is similar to a clathrate and has an ice-like crystal structure and can be characterized according to the hydrophobic effect. The extent of lipid solubility is determined by the unfavorable entropy contribution due to the ordering of the water structure according to the hydrophobic effect.

Micelles composed of ionic surfactants have an electrostatic attraction to the ions that surround them in solution, the latter known as counterions. Although the closest counterions partially mask a charged micelle (by up to 90%), the effects of micelle charge affect the structure of the surrounding solvent at appreciable distances from the micelle. Ionic micelles influence many properties of the mixture, including its electrical conductivity. Adding salts to a colloid containing micelles can decrease the strength of electrostatic interactions and lead to the formation of larger ionic micelles. This is more accurately seen from the point of view of an effective charge in hydration of the system.

TEXT 5

ENVIRONMENTAL CHEMISTRY

 

Environmental chemistry is the scientific study of the chemical and biochemical phenomena that occur in natural places. It should not be confused with green chemistry, which seeks to reduce potential pollution at its source. It can be defined as the study of the sources, reactions, transport, effects, and fates of chemical species in the air, soil, and water environments; and the effect of human activity and biological activity on these. Environmental chemistry is an interdisciplinary science that includes atmospheric, aquatic and soil chemistry, as well as heavily relying on analytical chemistry and being related to environmental and other areas of science. Environmental chemistry involves first understanding how the uncontaminated environment works, which chemicals in what concentrations are present naturally, and with what effects. Without this it would be impossible to accurately study the effects humans have on the environment through the release of chemicals. Environmental chemists draw on a range of concepts from chemistry and various environmental sciences to assist in their study of what is happening to a chemical species in the environment. Important general concepts from chemistry include understanding chemical reactions and equations, solutions, units, sampling, and analytical techniques.

Contamination. A contaminant is a substance present in nature at a level higher than typical levels or that would not otherwise be there. This may be due to human activity. The term contaminant is often used interchangeably with pollutant, which is a substance that has a detrimental impact on the surrounding environment. Whilst a contaminant is sometimes defined as a substance present in the environment as a result of human activity, but without harmful effects, it is sometimes the case that toxic or harmful effects from contamination only become apparent at a later date. The "medium" (e.g. soil) or organism (e.g. fish) affected by the pollutant or contaminant is called a receptor, whilst a sink is a chemical medium or species that retains and interacts with the pollutant.

Environmental indicators. Chemical measures of water quality include dissolved oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD), total dissolved solids (TDS), pH, nutrients (nitrates and phosphorus), heavy metals (including copper, zinc, cadmium, lead and mercury), and pesticides.

Applications. The major application areas of environmental chemistry are as below.

Risk or hazard assessments of environmental impact. The risk factor of the chemicals is determined for safety of environment. This is detected by various techniques.

Management of environment. Environmental chemistry studies the development of new chemical products and their behavior in the atmosphere. The complete life cycle of chemical is used for proper handling and storage methods of chemicals that are helpful for detecting the adverse effect on environment.

Groundwater protection. The ground water is polluted by polluted soil and waste site leachate. So the pollutant identification is done in environmental chemistry by knowing the concentration, distribution and fate of hazardous chemicals.

Protection of surface water. The effect of contaminants in the water and sediments phase is measured for checking the quality of surface water. This is done by sedimentation processes, bacteriological processes, radiation processes, etc.

Soil protection.The soil quality is checked by measuring the impact of soil contaminants on the soil. This is analyzed by various chemical and eco-toxicological indicators.

Cleaner production and waste management. This includes the management and re-use of waste and site remediation. The re-use and site remediation are done by analyzing the pollutants in environmental samples and knowing about their nature. The re-use of waste involves the innovative uses of waste products.

TEXT 6

CELL PHONE CHEMISTRY

A typical cell phone contains some of the most valuable elements on Earth. With everything from gold to silver, it’s like having a little treasure chest in your pocket. A smart phone is packed with at least 40 elements.

BATTERY. When you turn on your phone, positively charged lithium ions move through a lithium-salt solution that conducts electricity. Electrons flow out of the battery, producing the electric current that powers your phone. The rechargeable battery’s casing is made of aluminum.

CIRCUITRY. The circuit board has gold, copper, and silver—good electrical conductors. The connectors (pins that join circuits to the circuit board) are coated in gold because it’s highly resistant to corrosion. The wiring is copper. Solder—an alloy of tin, silver, and copper—binds parts of the circuit board.

COMPUTER CHIP. The chip is the phone’s brain. It has many transistors made of antimony, phosphorus, and gallium arsenide (GaAs). Transistors act as paths and switches that tell the phone to follow or stop following commands. The chip is embedded with silicon—which has low conductivity—to channel electricity only through the conductive transistors.

TOUCH SCREEN. A thin layer of indium tin oxide—a mixture of indium oxide (In2O3) and tin oxide (SnO2)—conducts electricity. When you touch the screen, a change in the electrical field occurs and communicates your finger’s location to the phone’s chip.

GLASS. Smartphone screens contain aluminosilicate glass, made from the compounds alumina (Al2O3) and silica (SiO2). If you’ve ever dropped your phone and its screen has stayed intact, you can thank potassium ions (atoms that have gained or lost electrons). They help strengthen the glass.

DISPLAY. A cell phone’s display contains several rare earth elements. These elements are spread out widely in Earth’s crust, making them hard to mine. Small quantities of yttrium, europium, and dysprosium help produce the colors on the phone’s liquid crystal display (LCD) screen. Gadolinium, lanthanum, and terbium give the screen its glow.

MICROPHONE AND SPEAKERS. The microphone’s wafer-thin diaphragm, which vibrates when sound waves strike it, is made of nickel. The vibrations are converted into an electrical current that becomes the audio signal.

Magnets vibrate in the speaker to create audible sound. Magnets of neodymium (Nd2Fe14B) are used because they’re the strongest magnets, so even though they’re small, they’re powerful.

 

TEXT 7

ALCOHOLS

In chemistry, an alcohol is any organic compound in which the hydroxyl functional group (-OH) is bound to a saturated carbon atom. The term alcohol originally referred to the primary alcohol ethyl alcohol (ethanol), the predominant alcohol in alcoholic beverages.

Alcohols have an odor that is often described as “biting” and as “hanging” in the nasal passages. Ethanol has a slightly sweeter (or more fruit-like) odor than the other alcohols.

In general, the hydroxyl group makes the alcohol molecule polar. Those groups can form hydrogen bonds to one another and to other compounds (except in certain large molecules where the hydroxyl is protected by steric hindrance of adjacent groups). This hydrogen bonding means that alcohols can be used as protic solvents. Two opposing solubility trends in alcohols are: the tendency of the polar OH to promote solubility in water, and the tendency of the carbon chain to resist it. Thus, methanol, ethanol, and propanol are miscible in water because the hydroxyl group wins out over the short carbon chain. Butanol, with a four-carbon chain, is moderately soluble because of a balance between the two trends. Alcohols of five or more carbons (pentanol and higher) are effectively insoluble in water because of the hydrocarbon chain's dominance. All simple alcohols are miscible in organic solvents.

Because of hydrogen bonding, alcohols tend to have higher boiling points than comparable hydrocarbons and ethers. The boiling point of the alcohol ethanol is 78.29 °C, compared to 69 °C for the hydrocarbon hexane (a common constituent of gasoline), and 34.6 °C for diethyl ether.

Alcohols, like water, can show either acidic or basic properties at the -OH group. With a pKa of around 16-19, they are, in general, slightly weaker acids than water, but they are still able to react with strong bases such as sodium hydride or reactive metals such as sodium. The salts that result are called alkoxides, with the general formula RO- M+.

Meanwhile, the oxygen atom has lone pairs of nonbonded electrons that render it weakly basic in the presence of strong acids such as sulfuric acid. For example, with methanol.

Alcohols can also undergo oxidation to give aldehydes, ketones, or carboxylic acids, or they can be dehydrated to alkenes. They can react to form ester compounds, and they can (if activated first) undergo nucleophilic substitution reactions. The lone pairs of electrons on the oxygen of the hydroxyl group also makes alcohols nucleophiles. For more details, see the reactions of alcohols section below.

As one moves from primary to secondary to tertiary alcohols with the same backbone, the hydrogen bond strength, the boiling point, and the acidity typically decrease.

Hydroxyl groups (-OH), found in alcohols, are polar and therefore hydrophilic (water loving) but their carbon chain portion is non-polar which make them hydrophobic. The molecule increasingly becomes overall more nonpolar and therefore less soluble in the polar water as the carbon chain becomes longer. Methanol has the shortest carbon chain of all alcohols (one carbon atom) followed by ethanol (two carbon atoms.)

Alcohols have applications in industry and science as reagents or solvents. Because of its relatively low toxicity compared with other alcohols and ability to dissolve non-polar substances, ethanol can be used as a solvent in medical drugs, perfumes, and vegetable essences such as vanilla. In organic synthesis, alcohols serve as versatile intermediates.

TEXT 8

KETO-ENOL TAUTOMERISM


In organic chemistry, keto–enol tautomerism refers to a chemical equilibrium between a keto form (a ketone or an aldehyde) and an enol (an alcohol). The enol and keto forms are said to be tautomers of each other. The interconversion of the two forms involves the movement of alpha hydrogen and the shifting of bonding electrons; hence, the isomerism qualifies as tautomerism.

A compound containing a carbonyl group (C=O) is normally in rapid equilibrium with an enol tautomer, which contains a pair of doubly bonded carbon atoms adjacent to a hydroxyl (−OH) group, C=C-OH. The keto form predominates at equilibrium for most ketones. Nonetheless, the enol form is important for some reactions. The deprotonated intermediate in the interconversion of the two forms, referred to as an enolate anion, is important in carbonyl chemistry, in large part because it is a strong nucleophile.

Normally, the keto–enol tautomerization chemical equilibrium is highly thermodynamically driven, and at room temperature the equilibrium heavily favors the formation of the keto form. A classic example for favoring the keto form can be seen in the equilibrium between vinyl alcohol and acetaldehyde (K = [enol]/ [keto] ≈ 3 × 10−7). However, it is reported that in the case of vinyl alcohol, formation of a stabilized enol form can be accomplished by controlling the water concentration in the system and utilizing the kinetic favorability of the deuterium produced kinetic isotope effect (kH+/kD+ = 4.75, kH2O/kD2O = 12). Deuterium stabilization can be accomplished through hydrolysis of a ketene precursor in the presence of a slight stoichiometric excess of heavy water (D2O). Studies show that the tautomerization process is significantly inhibited at ambient temperatures ( kt ≈ 10−6 M/s), and the half life of the enol form can easily be increased to t1/2 = 42 minutes for first order hydrolysis kinetics.

Mechanism. The acid catalyzed conversion of an enol to the keto form proceeds by a two step mechanism in an aqueous acidic solution. For this, it is necessary that the alpha carbon (the carbon closest to functional group) contains at least one hydrogen atom known as alpha hydrogen.This atom is removed from the alpha carbon and bonds to the oxygen of the carbonyl carbon to form the enol tautomer. The existence of hydrogen atom at alpha carbon is necessary but not sufficient condition for enolization to occur. To be acidic, the alpha hydrogen should be positioned such that may line up parallel with antibonding pi-orbital of the carbonyl group. The hyperconjugation of this bond with C–H bond at alpha carbon reduces the electron density out of C–H bond and weakens it. Thus the alpha hydrogen becomes acidic. When this requirement is not enforced, for example in the adamantanone or other polycyclic ketones, the enolization is impossible or very slow.

First, the exposed electrons of the C=C double bond of the enol are donated to a hydronium ion (H3O+). This addition follows Markovnikov's rule, thus the proton is added to the carbon with more hydrogens. This is a concerted step with the oxygen in the hydroxyl group donating electrons to produce the eventual carbonyl group.

One of the early investigators into keto–enol tautomerism was Emil Erlenmeyer. His Erlenmeyer rule, developed in 1880, states that all alcohols in which the hydroxyl group is attached directly to a double-bonded carbon atom become aldehydes or ketones. This conversion occurs because the keto form is, in general, more stable than its enol tautomer. The keto form is therefore favored at equilibrium because it is the lower energy form.

Keto–enol tautomerism is important in several areas of biochemistry. The high phosphate-transfer potential of phosphoenolpyruvate results from the fact that the phosphorylated compound is "trapped" in the less stable enol form, whereas after dephosphorylation it can assume the keto form. Rare enol tautomers of the bases guanine and thymine can lead to mutation because of their altered base-pairing properties.

 

 

TEXT 9

COORDINATION CHEMISTRY

Complexes or coordination compoundsare molecules that posess a metal center that is bound to ligands (atoms, ions, or molecules that donate electrons to the metal). These complexes can be neutral or charged. When the complex is charged, it is stabilized by neighboring counter-ions.

Coordination chemistry emerged from the work of Alfred Werner, a Swiss chemist who examined different compounds composed of cobalt (III) chloride and ammonia. Upon the addition of hydrochloric acid, Werner observed that ammonia could not be completely removed. He then proposed that the ammonia must be bound more tightly to the central cobalt ion. However, when aqueous silver nitrate was added, one of the products formed was solid silver chloride. The amount of silver chloride formed was related to the number of ammonia molecules bound to the cobalt (III) chloride. For example, when silver nitrate was added to CoCl3·6NH3, all three chlorides were converted to silver chloride. However, when silver nitrate was added to CoCl3·5NH3, only 2 of the 3 chlorides formed silver chloride. When CoCl3·4NH3 was treated with silver nitrate, one of the three chlorides precipitated as silver chloride.

The resulting observations suggested the formation of complex or coordination compounds. In the inner coordination sphere, which is also referred to in some texts as the first sphere, ligands are directly bound to the central metal. In the outer coordination sphere, sometimes referred to as the second sphere, other ions are attached to the complex ion. Werner was awarded the Nobel Prize in 1913 for his coordination theory. The following table is a summary of Werner's observations:

 

Initial compound Resulting compounds upon adding AgNO3
CoCl3·6NH3 [Co(NH3)6]3+(Cl-)3
CoCl3·5NH3 [Co(NH3)5Cl]2+(Cl-)2
CoCl3·4NH3 [Co(NH3)4Cl2]+(Cl-)
CoCl3·3NH3 [Co(NH3)3Cl3]

 

As the table above shows, the complex ion [Co(NH3)6]3+ is countered by the three chloride ions. The multi-level binding of coordination complexes play an important role in determining the dissociation of these complexes in aqueous solution. For example, [Co(NH3)5Cl]2+(Cl-)2 dissociates into 3 ions while [Co(NH3)4Cl2 ]+(Cl-) dissociates into 2 ions. By applying a current through the aqueous solutions of the resulting complex compounds, Werner measured the electrical conductivity and thus the dissociation properties of the complex compounds. The results confirmed his hypothesis of the formation of complex compounds. It is important to note that the above compounds have a coordination number of 6, which is a common coordination number for many inorganic complexes. Coordination numbers for complex compounds typically range from 1 to 16.

Properties of Coordination Complexes.Some methods of verifying the presence of complex ions include studying its chemical behavior. This can be achieved by observing the compounds' color, solubility, absorption spectrum, magnetic properties, etc. The properties of complex compounds are separate from the properties of the individual atoms. By forming coordination compounds, the properties of both the metal and the ligand are altered.

Metal-ligand bonds are typically thought of Lewis acid-base interactions. The metal atom acts as an electron pair acceptor (Lewis acid), while the ligands act as electron pair donors (Lewis base). The nature of the bond between metal and ligand is stronger than intermolecular forces because they form directional bonds between the metal ion and the ligand, but are weaker than covalent bonds and ionic bonds.

Common Ligands.Monodentate ligands donate one pair of electrons to the central metal atoms. An example of these ligands are the haldide ions (F-, Cl-, Br-, I-). Polydentate ligands, also called chelates or chelating agents, donate more than one pair of electrons to the metal atom forming a stronger bond and a more stable complex. A common chelating agent is ethylenediamine (en), which, as the name suggests, contains two ammines or: NH2 sites which can bind to two sites on the central metal. An example of a tridentate ligand is bis-diethylenetriammine. An example of such a coordination complex is bis-diethylenetriamine cobalt III.

Complex ions can form many compounds by binding with other complex ions in multiple ratios. This leads to many combinations of coordination compounds. The structures of certain coordination compounds can also have isomers, which can change their interactions with other chemical agents. The binding between metal and ligands is studied in metals, tetrahedral, and octahedral structures. There are many pharmaceutical and biological applications of coordination complexes and their isomers.

 

TEXT 10

LIQUID-LIQUID EXTRACTION

Liquid–liquid extraction (LLE) consists in transferring one (or more) solute(s) contained in a feed solution to another immiscible liquid (solvent). The solvent that is enriched in solute(s) is called extract. The feed solution that is depleted in solute(s) is called raffinate.

Liquid–liquid extraction also known as solvent extraction and partitioning, is a method to separate compounds based on their relative solubilities in two different immiscible liquids, usually water and an organic solvent. It is an extraction of a substance from one liquid into another liquid phase. Liquid–liquid extraction is a basic technique in chemical laboratories, where it is performed using a variety of apparatus, from separatory funnels to countercurrent distribution equipment. This type of process is commonly performed after a chemical reaction as part of the work-up.

The term partitioning is commonly used to refer to the underlying chemical and physical processes involved in liquid–liquid extraction, but on another reading may be fully synonymous with it. The term solvent extraction can also refer to the separation of a substance from a mixture by preferentially dissolving that substance in a suitable solvent. In that case, a soluble compound is separated from an insoluble compound or a complex matrix.

Solvent extraction is used in nuclear reprocessing, ore processing, the production of fine organic compounds, the processing of perfumes, the production of vegetable oils and biodiesel, and other industries.

Liquid–liquid extraction is possible in non-aqueous systems: In a system consisting of a molten metal in contact with molten salts, metals can be extracted from one phase to the other. This is related to a mercury electrode where a metal can be reduced, the metal will often then dissolve in the mercury to form an amalgam that modifies its electrochemistry greatly. For example, it is possible for sodium cations to be reduced at a mercury cathode to form sodium amalgam, while at an inert electrode (such as platinum) the sodium cations are not reduced. Instead, water is reduced to hydrogen. A detergent or fine solid can be used to stabilize an emulsion, or third phase.

 

 

APPENDICES

I

CHEMICAL ELEMENTS

 

Acactinium [æk'tiniəm] актиний

Ag silver ['silvə] серебро

Al aluminium ['ælə'miniəm] алюминий

Am americium [,æmə'risiəm] америций

Arargon ['a:gɔn] аргон

Asarsenic ['a:snik] мышьяк

At astatine ['æstəti:n] астат

Au gold [gɔuld] золото

B boron ['bɔ:rɔn] бор

Ba barium ['beəriəm] барий

Beberyllium [bə'riliəm] бериллий

Bi bismuth ['bizməθ] висмут

Bk berkelium [bə'ki:liəm] берклий

Br bromine ['broumi:n] бром

Ccarbon ['ka:bən] углерод

Cacalcium ['kælsiəm] кальций

Cdcadmium ['kædmiəm] кадмий

Ce cerium ['siəriəm] церий

Cfcalifornium [ˌkælə'fɔ:niəm] калифорний

Cl chlorine ['klɔ:ri:n] хлор

Cm curium ['kjuəriəm] кюрий

Co cobalt ['kəubɔ:lt] кобальт

Cr chromium ['krəumiəm] хром

Cs c(a)esium ['si:ziəm] цезий

Cu copper ['kɔpə] медь

Dy dysprosium [dis'prəuziəm] диспрозий

Ererbium ['ə:biəm] эрбий

Eseinsteinium [ain'stainiəm] эйнштейний

Eu europium [ju:'rəupiəm] европий

Ffluorine ['fluəri:n] фтор

Fe iron ['aiən] железо

Fm fermium ['fə:miəm] фермий

Frfrancium ['frænsiəm] франций

Ga gallium ['gæliəm] галлий

Gd gadolinium [ˌgædə'liniəm] гадолиний

Ge germanium [dʒə:'meiniəm] германий

Hhydrogen ['haidrədʒən] водород

Hehelium ['hi:liəm] гелий

Hfhafnium ['hæfniəm] гафний

Hg mercury ['mə:kjuri] ртуть

Hoholmium ['həulmiəm] гольмий

Iiodine ['aiədi:n] йод

Inindium ['indiəm] индий

Ir iridium [i'ridiəm] иридий

Kpotassium [pə'tæsiəm] калий

Krkrypton ['kriptɔn] криптон

Kukurchatovium [ˌk ə:t∫ə'təuviəm] курчатовий

La lanthanum ['lænθənəm] лантан

Li lithium ['liθiəm] литий

Ln lawrencium [lə'rensiəm] лоуренсий

Lu lutecium [lə'ti:∫əm] лютеций

Md mendelevium [ˌmendə'li:viəm] менделевий

Mg magnesium [mæg'ni:zjəm] магний

Mn manganese [ˌmængə'ni:z] марганец

Mo molybdenum [mə'libdənəm] молибден

Nnitrogen ['naitrədʒən] азот

Na sodium ['səudiəm] натрий

Nbniobium [nai'əubiəm] ниобий

Nd neodymium [ˌni: əu'dimiəm] неодим

Neneon ['ni: ən] неон

Ninickel [nikl] никель

No nobelium [nəu'bi:liəm] нобелий

Npneptunium [nep'tju:niəm] нептуний

Nsnielsbohrium [ni:ls'bɔ:riəm] нильсборий

O oxygen ['ɔksidʒən] кислород

Ososmium ['ɔzmiəm] осмий

P phosphorus ['fɔsfərəs] фосфор

Pa protactinium [ˌprəutæk'tiniəm] протактиний

Pblead [led] свинец

Pdpalladium [pə'leidiəm] палладий

Pm promethium [prəu'mi:θiəm] прометий

Popolonium [pə'ləuniəm] полоний

Pr praseodymium [ˌpreiziəu'dimiəm] празеодим

Ptplatinum [plætinəm] платина

Pu plutonium [plu:'təuniəm] плутоний

Raradium ['reidiəm] радий

Rb rubidium [rubidium] рубидий

Rerhenium ['ri:niəm] рений

Rh rhodium ['rəudiəm] родий

Rnradon ['reidɔn] радон

Ruruthenium [ru'θi:niəm] рутений

Ssulphur ['sʌlfə] сера

Sb antimony ['æntiməni] сурьма

Scscandium ['skændiəm] скандий

Seselenium [sə'li:niəm] селен

Si silicion ['silikən] кремний

Sm samarium [sə'meəriəm] самарий

Sn tin [tin] олово

Srstrontium ['strɔntiəm] стронций

Tatantalum ['tæntələm] тантал

Tb terbium ['tə:diəm] тербий

Tc technetium [tek'ni:∫iəm] технеций

Te tellurium [te'luəriəm] теллур

Th thorium ['θɔ:riəm] торий

Ti titanum [tai'teinjəm] титан

Tl thallium ['θæliəm] таллий

Tm tullium ['tʌliəm] тулий

Uuranium [juə'reiniəm] уран

V vanadium [və'neidiəm] ванадий

Wtungsten ['tʌŋstən] вольфрам

Xe xenon ['zi:nɔn] ксенон

Y yttrium ['itriəm] иттрий

Yb ytterbium [i'tə:biəm] иттербий

Zn zinc [ziŋk] цинк

Zrzirconium [zə:'kəuniəm] цирконий

 

 

 

 

 

 

II






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