Application of Transition Metals

Application of Transition Metals The term transition metal (sometimes also called a transition element) has two possible meanings: In the past it referred to any element in the d-block of the periodic table, which includes groups 3 to 12 on the periodic table. All elements in the d-block are metals (In actuality, the f-block is also included in the form of the lanthanide and actinide series). It also states that a transition metal is an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell. Group 12 elements are not transition metals in this definition. Introduction to application of transition metals: The use of transition metals in the synthesis was taken up slowly by organic chemists. This is at first surprising because the industrial use of transition metals has a much long history hydroformylation using cobalt began in the 1930s. The Mond process using nickel tetra carbonyl was developed in the 19 century. Industry was willing to accept and uses processes that it could not understand black box reactions as long as they were profitable. Academics were handicapped by the desire to understand the chemistry. This was impossible until the ideas about chemical bonding and the necessary instrumentation matured in the years in the Second World War. Even with in this place, the impact of transition metals on the organic synthesis came late possibly because of the many fantastic main group reagents appeared. Application of Transition Metals: The application of transition metals is as follows: 1. Transition metals are applied in the organic reactions. Transition metals complex under goes a series of reactions that are generally unlike those main group compounds. The most fundamental is the simple coordination and dissociation of ligands. Dissociation may also be achieved by destruction of a ligand. This is often done by the oxidation of co and co2 using an amide oxide. 2. Transition metals are applied in the synthesis of metal hydride. M=C=O + OH- ====> M-H + CO2 Here metal carbonyl group reacts with hydroxide to give metal hydride and carbon dioxide. Hydrides such as, sodium borohydride, lithium aluminium hydride, diisobutylaluminium hydride (DIBAL) and super hydride, are commonly used as reducing agents in chemical synthesis. The hydride adds to an electrophilic center, typically unsaturated carbon. Hydrides such as sodium hydride and potassium hydride are used as strong bases in organic synthesis. The hydride reacts with the weak Bronsted acid releasing H2. Hydrides such as calcium hydride are used as desiccants, i.e. drying agents, to remove trace water from organic solvents. The hydride reacts with water forming hydrogen and hydroxide salt. The dry solvent can then be distilled or vac transferred from the solvent pot. Hydrides are of important in storage battery technologies such as Nickel-metal hydride battery. Various metal hydrides have been examined for use as a means of hydrogen storage for fuel cell-powered electric cars and other purposed aspects of a hydrogen economy. Hydride intermediates are key to understanding a variety of homogeneous and heterogeneous catalytic cycles as well as enzymatic activity. Hydroformylation catalysts and hydrogenase both involve hydride intermediates. The energy carrier NADH reacts as a hydride donor or hydride equivalent. 3. Transition metal used in the complexes in fluorescence cell imaging. Transition metal complexes have often been proposed as useful fluorophores for cell imaging due to their attractive photo physical attributes, but until very recently their actual applications have been scarce and largely limited to ruthenium complexes in DNA and oxygen sensing. 4. Transition metal used as Catalysts. Some transition metals are good catalysts. For example: most automobiles have an emissions-control device called a catalytic converter. This device contains a screen of platinum or palladium along with rhodium, a metal. The presence of the transition metals, along with the heat of combustion generated by an automobile engine causes an exhaust coming from an internal combustion engine to be broken down from partially burned hydrocarbon compounds into less harmful compounds such as water vapour and carbon dioxide. Catalytic applications of transition metals in organic synthesis:- OXIDATION REACTIONS: The epoxidation, dihydroxylation and aminohydroxylation reactions of alkenes, especially their asymmetric variants, continue to attract considerable attention. The basic principles were covered in the previous review. The use of fluorous solvents has now been demonstrated formany transition metal catalysed reactions. One advantage that they offer for catalyticepoxidation is the fact that molecularoxygen has a high solubility in fluorous solvents. The combination of O2 with pivalaldehyde and manganese catalysts hasbeen shown to be effective for epoxidation of alkenes in aracemic and enantioselective sense. The fluorous soluble ligand afforded a manganese complex which was insoluble incommon organic solvents, but soluble in the fluorous phase.Indene was converted into indene oxide with high enantioselectivity,although other substrates afforded low selectivity The fluorous phase, containing the active catalyst,could be recycled. Manganese salen complexes have also now been successfullyimmobilised within polymer supports, and still provide high Whilst the enantiomerically pure manganese salen complexes are still often the most enantio selective available for epoxidation of unfunctionalised alkenes, alternative systems are often reported. For example, End and Pfaltz have used rutheniumbis (oxazoline) complexes to provide up to 69% ee in the epoxidation of stilbene. The use of methyltrioxorhenium as a catalyst for epoxidationcontinues to attract attention. Herrmann and co-workershave shown that a combination of methyltrioxorhenium withpyrazole affords a highly efficient catalyst for the epoxidation of alkenes. Styrene was converted cleanly into styrene oxide with this catalytic combination. Reduction reactions The reduction of various functional groups can often be achieved using transition metal catalysts and a suitable reducing agent: often molecular hydrogen, silanes, boranes orhydrides. Amongst all of the possibilities, metal-catalysed hydrogenation has been the most widely studied, especially asan asymmetric process.Some recently reported examples of rhodium-catalyse dasymmetric hydrogenation of alkenes include the conversion ofthe enamide into the derivatised amino alcohols and the regioselective hydrogenation of dienyl acetate into the allyl acetate both using the Me-DuPhos ligand .Reports of new ligands for asymmetric hydrogenation of alkenes continue to appear, often providing highly selective examples.Ruthenium catalysed hydrogenation of alkenes is also popular,and an interesting example has been provided by Bruneau,Dixneuf and co-workers. The achiral substrate is hydrogenatedwith an enantiomerically pure ruthenium complex into compound , which behaves as propionic acid attachedt o a chiral auxiliary. The achiral auxiliary in the substrate is converted into an enantiomerically enriched one prior to a subsequent auxiliary controlled functionalisation. Lewis acid catalysed reactions:- Lewis acids are able to catalyse a wide range of reactions. Theaddition of cyanide to aldehydes is one such reaction and hasbeen studied by many groups. Recently, North, Belokon andco-workers have used a titanium (salen) complex to catalyse the addition of trimethylsilylcyanide to benzaldehyde withlow catalyst loadings. Less work has been reported on theenantioselective addition of cyanide to imines, although it providesa useful route to ÃŽÂ ±-amino acids (Strecker synthesis). However, there have been several reports of the enantio selective variant of this reaction by aluminium catalysts,non-metallic catalysts, and with the zirconium catalysts, reported here. The imine is converted into the ÃŽÂ ±-aminonitrile with good yield and enantio selectivity Scandium triflate is a good catalyst for the allylation of aldehydes with allylsilanes and stannanes. Aggarwal and Vennallhave detailed the allylation of aldehydes followed by in situ acylation.36 Benzaldehyde allylsilane and acetic anhydride undergo coupling to provide the homoallylic acetate withscandium triflate as the catalyst Kobayashi and co-workers have shown that a three component system comprising of benzaldehyde an amine,such as aniline and allylstannane affo rds the homoallylicamine The reaction works more quickly in the presence of sodium dodecylsulfate SDS, which provides amicellar system .The allylation of isolated imines with enantiomerically pure palladium complexes has been achieved with up to 82%enantiomeric excess. Catalytic coupling reactions:- The formation of C-C bonds, as well as C-X bonds can becatalysed by many transition metals, although palladium complexesseem to have a greater scope than other metals. The useof catalytic coupling reactions to provide biaryls has recently been reviewed. 5. REAL LIFE APPLICATIONS: The fact that the transition elements are all metals means that they are lustrous or shiny in appearance, and malleable, meaning that they can be molded into different shapes without breaking. They are excellent conductors of heat and electricity, and tend to form positive ions by losing electrons. Generally speaking, metals are hard, though a few of the transition metals-as well as members of other metal families-are so soft they can be cut with a knife. Like almost all metals, they tend to have fairly high melting points, and extremely high boiling points. Many of the transition metals, particularly those on periods 4, 5, and 6, form useful alloys-mixtures containing more than one metal-with one another, and with other elements. Because of their differences in electron configuration, however, they do not always combine in the same ways, even within an element. Iron, for instance, sometimes releases two electrons in chemical bonding, and at other times three. ABUNDANCE OF THE TRANSITION METALS: Iron is the fourth most abundant element on Earth, accounting for 4.71% of the elemental mass in the planets crust. Titanium ranks 10th, with 0.58%, and manganese 13th, with 0.09%. Several other transition metals are comparatively abundant: even gold is much more abundant than many other elements on the periodic table. However, given the fact that only 18 elements account for 99.51% of Earths crust, the percentages for elements outside of the top 18 tend to very small. In the human body, iron is the 12th most abundant element, constituting 0.004% of the bodys mass. Zinc follows it, at 13th place, accounting for 0.003%. Again, these percentages may not seem particularly high, but in view of the fact that three elements-oxygen, carbon, and hydrogen-account for 93% of human elemental body mass, there is not much room for the other 10 most common elements in the body. Transition metals such as copper are present in trace quantities within the body as well. (industrial effulent) DIVIDING THE TRANSITION METALS INTO GROUPS. There is no easy way to group the transition metals, though certain of these elements are traditionally categorized together. These do not constitute families as such, but they do provide useful ways to break down the otherwise rather daunting 40-element lineup of the transition metals. In two cases, there is at least a relation between group number on the periodic table and the categories loosely assigned to a collection of transition metals. Thus the coinage metals-copper, silver, and gold-all occupy Group 9 on the periodic table. These have traditionally been associated with one another because their resistance to oxidation, combined with their malleability and beauty, has made them useful materials for fashioning coins. Likewise the members of the zinc group-zinc, cadmium, and mercury-occupy Group 10 on the periodic table. These, too, have often been associated as a miniature unit due to common properties. Members of the platinum group-platinum, iridium, osmium, palladium, rhodium, and ruthenium-occupy a rectangle on the table, corresponding to periods 5 and 6, and groups 6 through 8. What actually makes them a group, however, is the fact that they tend to appear together in nature. Iron, nickel, and cobalt, found alongside one another on Period 4, may be grouped together because they are all magnetic to some degree or another. This is far from the only notable characteristic about such metals, but provides a convenient means of further dividing the transition metals into smaller sections. To the left of iron on the periodic table is a rectangle corresponding to periods 4 through 6, groups 4 through 7. These 11 elements-titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, and rhenium-are referred to here as alloy metals. This is not a traditional designation, but it is nonetheless useful for describing these metals, most of which form important alloys with iron and other elements. One element was left out of the rectangle described in the preceding paragraph. This is technetium, which apparently does not occur in nature. It is lumped in with a final category, rare and artificial elements. It should be stressed that there is nothing hard and fast about these categories. The alloy metals are not the only ones that form alloys; nickel is used in coins, though it is not called a coinage metal; and platinum could be listed with gold and silver as precious metals. Nonetheless, the categories used here seem to provide the most workable means of approaching the many transition metals. GOLD. Gold almost needs no introduction: virtually everyone knows of its value, and history is full of stories about people who killed or died for this precious metal. Part of its value springs from its rarity in comparison to, say iron: gold is present on Earths crust at a level of about 5 parts per billion (ppb). Yet as noted earlier, it is more abundant than some metals. Furthermore, due to the fact that it is highly unreactive (reactivity refers to the tendency for bonds between atoms or molecules to be made or broken in such a way that materials are transformed), it tends to be easily separated from other elements. This helps to explain the fact that gold may well have been the first element ever discovered. No ancient metallurgist needed a laboratory in which to separate gold; indeed, because it so often keeps to itself, it is called a noble metal-meaning, in this context, set apart. Another characteristic of gold that made it valuable was its great malleability. In fact, gold is the most malleable of all metals: A single troy ounce (31.1 g) can be hammered into a sheet just 0.00025 in (0.00064 cm) thick, covering 68 ft  2  (6.3 m  2  ). Gold is one of the few metals that is not silver, gray, or white, and its beautifully distinctive color caught the eyes of metalsmiths and royalty from the beginning of civilization. Records from India dating back to 5000  B.C.  suggest a familiarity with gold, and jewelry found in Egyptian tombs indicates the use of sophisticated techniques among the goldsmiths of Egypt as early as 2600  B.C.  Likewise the Bible mentions gold in several passages. The Romans called it  aurum  (shining dawn), which explains its chemical symbol, Au. Gold is as popular as ever for jewelry and other decorative objects, of course, but for the most part, it is too soft to have many other commercial purposes. One of the few applications for gold, a good conductor of electricity, is in some electronic components. Also, the radioactive gold-198 isotope is sometimes implanted in tissues as a means of treating forms of cancer. SILVER. Like gold, silver has been a part of human life from earliest history. Usually it is considered less valuable, though some societies have actually placed a higher value on silver because it is harder and more durable than gold. In the seventh century  B.C.  , the Lydian civilization of Asia Minor (now Turkey) created the first coins using silver, and in the sixth century  B.C.  , the Chinese began making silver coins. Succeeding dynasties in China continued to mint these coins, round with square holes in them, until the early twentieth century. The Romans called silver  argentum,  and therefore today its chemical symbol is Ag. Its uses are much more varied than those of gold, both because of its durability and the fact that it is less expensive. Alloyed with copper, which adds strength to it, it makes sterling silver, used in coins, silverware, and jewelry. Silver nitrate compounds are used in silver plating, applied in mirrors and tableware. (Most mirrors today, however, use aluminum.) A large portion of the worlds silver supply is used by photographers for developing pictures. In addition, because it is an excellent conductor of heat and electricity, silver has applications in the electronics industry; however, its expense has led many manufacturers to use copper or aluminum instead. Silver is also present, along with zinc and cadmium, in cadmium batteries. Like gold, though to a much lesser extent, it is still an important jewelry-making component. COPPER. Most people think of pennies as containing copper, but in fact the penny is the only American coin that contains no copper alloys. Because the amount of copper necessary to make a penny today costs more than $0.01, a penny is actually made of zinc with a thin copper coating. Yet copper has long been a commonly used coinage metal, and long before that, humans used it for other purposes. Seven thousand years ago, the peoples of the Tigris-Euphrates river valleys, in what is now Iraq, were mining and using copper, and later civilizations combined copper with zinc to make bronze. Indeed, the history of prehistoric and ancient humans technological development is often divided according to the tools they made, the latter two of which came from transition metals: the Stone Age, the Bronze Age (c. 3300-1200  B.C.  ), and the Iron Age. Copper is also like its two close relatives in that it resists corrosion, and this makes it ideal for plumbing. Its use in making coins resulted from its anti-corrosive qualities, combined with its beauty: like gold, copper has a distinctive color. This aesthetic quality led to the use of copper in decorative applications as well: many old buildings used copper roofs, and the Statue of Liberty is covered in 300 thick copper plates. Why, then, is the famous statue not copper-colored? Because copper does eventually corrode when exposed to air for long periods of time. Over time, it develops a thin layer of black copper oxide, and as the years pass, carbon dioxide in the air leads to the formation of copper carbonate, which imparts a greenish color. The human body is about 0.0004% copper, though as noted, larger quantities of copper can be toxic. Copper is found in foods such as shell-fish, nuts, raisins, and dried beans. Whereas human blood has hemoglobin, a molecule with an iron atom at the center, the blood of lobsters and other large crustaceans contains hemocyanin, in which copper performs a similar function. ZINC. Together with copper, zinc appeared in another alloy that, like bronze, helped define the ancient world: brass. (The latter is mentioned in the Bible, for instance in the Book of Daniel,when King Nebuchadnezzar dreams of a statue containing brass and other substances, symbolizing various empires.) Used at least from the first millennium  B.C.  onward, brass appeared in coins and ornaments throughout Asia Minor. Though it is said that the Chinese purified zinc in about  A.D.  1000, the Swiss alchemist Paracelsus (1493-1541) is usually credited with first describing zinc as a metal. Bluish-white, with a lustrous sheen, zinc is found primarily in the ore sulfide sphalerite. The largest natural deposits of zinc are in Australia and the United States, and after mining, the metal is subjected to a purification and reduction process involving carbon. Zinc is used in galvanized steel, developed in the eighteenth century by Italian physicist Luigi Galvani (1737-1798). CADMIUM. In 1817, German chemist Friedrich Strohmeyer (1776-1835) was working as an inspector of pharmacies for the German state of Hanover. While making his rounds, he discovered that one pharmacy had a sample of zinc carbonate labeled as zinc oxide, and while inspecting the chemical in his laboratory, he discovered something unusual. If indeed it were zinc carbonate, it should turn into zinc oxide when heated, and since both compounds were white, there should be no difference in color. Instead, the mysterious compound turned a yellowish-orange. Strohmeyer continued to analyze the sample, and eventually realized that he had discovered a new element, which he named after the old Greek term for zinc carbonate,  kadmeia.  Indeed, cadmium typically appears in nature along with zinc or zinc compounds. Silvery white and lustrous or shiny, cadmium is soft enough to be cut with a knife, but chemically it behaves much like zinc: hence the idea of a zinc group. MERCURY. One of only two elements-along with bromine-that appears in liquid form at room temperature, mercury is both toxic and highly useful. The Romans called it  hydragyrum  (liquid silver), from whence comes its chemical symbol, Hg. Today, however, it is known by the name of the Romans god Mercury, the nimble and speedy messenger of the gods. Mercury comes primarily from a red ore called cinnabar, and since it often appears in shiny globules that form outcroppings from the cinnabar, it was relatively easy to discover. Several things are distinctive about mercury, including its bright silvery color. But nothing distinguishes it as much as its physical properties-not only its liquidity, but the fact that it rolls rapidly, like the fleet-footed god after which it is named. Its surface tension (the quality that causes it to bead) is six times greater than that of water, and for this reason, mercury never wets the surfaces with which it comes in contact. Mercury, of course, is widely used in thermometers, an application for which it is extremely well-suited. In particular, it expands at a uniform rate when heated, and thus a mercury thermometer (unlike earlier instruments, which used water, wine, or alcohol) can be easily calibrated. (Note that due to the toxicity of the element, mercury thermometers in schools are being replaced by other types of thermometers.) At temperatures close to absolute zero, mercury loses its resistance to the flow of electric current, and therefore it presents a promising area of research with regard to superconductivity. IRON. In its purest form, iron is relatively soft and slightly magnetic, but when hardened, it becomes much more so. As with several of the elements discovered long ago, iron has a chemical symbol (Fe) reflecting an ancient name, the Latin  ferrum.  But long before the Romans ancestors arrived in Italy, the Hittites of Asia Minor were purifying iron ore by heating it with charcoal over a hot flame. The ways in which iron is used are almost too obvious (and too numerous) to mention. If iron and steel suddenly ceased to exist, there could be no skyscrapers, no wide-span bridges, no ocean liners or trains or heavy machinery or automobile frames. Furthermore, alloys of steel with other transition metals, such as tungsten and niobium, possess exceptionally great strength, and find application in everything from hand tools to nuclear reactors. Then, of course, there are magnets and electromagnets, which can only be made of iron and/or one of the other magnetic elements, cobalt and nickel. In the human body, iron is a key part of hemoglobin, the molecule in blood that transports oxygen from the lungs to the cells. If a person fails to get sufficient quantities of iron-present in foods such as red meat and spinach-the result is anemia, characterized by a loss of skin color, weakness, fainting, and heart palpitations. Plants, too, need iron, and without the appropriate amounts are likely to lose their color, weaken, and die. COBALT. Isolated in about 1735 by Swedish chemist Georg Brandt (1694-1768), cobalt was the first metal discovered since prehistoric, or at least ancient, times. The name comes from  Kobald,  German for underground gnome, and this reflects much about the early history of cobalt. In legend, the Kobalden were mischievous sprites who caused trouble for miners, and in real life, ores containing the element that came to be known as cobalt likewise caused trouble to men working in mines. Not only did these ores contain arsenic, which made miners ill, but because cobalt had no apparent value, it only interfered with their work of extracting other minerals. Yet cobalt had been in use by artisans long before Brandts isolated the element. The color of certain cobalt compounds is a brilliant, shocking blue, and this made it popular for the coloring of pottery, glass, and tile. The element, which makes up less than 0.002% of Earths crust, is found today primarily in ores extracted from mines in Canada, Zaire, and Morocco. One of the most important uses of cobalt is in a highly magnetic alloy known as alnico, which also contains iron, nickel, and aluminum. Combined with tungsten and chromium, cobalt makes stellite, a very hard alloy used in drill bits. Cobalt is also applied in jet engines and turbines. NICKEL. Moderately magnetic in its pure form, nickel had an early history much like that of cobalt. English workers mining copper were often dismayed to find a metal that looked like copper, but was not, and they called it Old Nicks copper-meaning that it was a trick played on them by Old Nick, or the devil. The Germans gave it a similar name:  Kupfernickel,  or imp copper. Though nickel was not identified as a separate metal by Swedish mineralogist Axel Fredrik Cronstedt (1722-1765) until the eighteenth century, alloys of copper, silver, and nickel had been used as coins even in ancient Egypt. Today, nickel is applied, not surprisingly, in the American five-cent piece-that is, the nickel-made from an alloy of nickel and copper. Its anti-corrosive nature also provides a number of other applications for nickel: alloyed with steel, for instance, it makes a protective layer for other metals. PLATINUM. First identified by an Italian physician visiting the New World in the mid-sixteenth century, platinum-now recognized as a precious metal-was once considered a nuisance in the same way that nickel and cadmium were. Miners, annoyed with the fact that it got in the way when they were looking for gold, called it  platina,  or little silver. One of the reasons why platinum did not immediately catch the worlds fancy is because it is difficult to extract, and typically appears with the other metals of the platinum group: iridium, osmium, palladium, rhodium, and ruthenium. Only in 1803 did English physician and chemist William Hyde Wollaston (1766-1828) develop a means of extracting platinum, and when he did, he discovered that the metal could be hammered into all kinds of shapes. Platinum proved such a success that it made Wollaston financially independent, and he retired from his medical practice at age 34 to pursue scientific research. Today, platinum is used in everything from thermometers to parts for rocket engines, both of which take advantage of its ability to with stand high temperatures. 6. Application of transition metals complex formation in gas chromatography. we will be discusing applications of superselective liquid phases containing transition metal salts or complexes in gas chromatography Introduction: Metal complexation may be used for four purposes in gas chromatography: to help the separation of certain compounds present in the sample. In this case complexation is performed by using a stationary phase containing a metal; to utilize GC for the calculation of stability constants orother physico-chemical data; to analyse the metals themselves, by making organic volatile complexes and analysing them by GC; to increase sensitivity for inorganic and organic compounds by forming metal complexes and utilize e.g. an electron capture detector which has an increased sensitivity for such compounds. The present review discusses only the first two of these four application fields. The effect of the formation of eleetron-donor-acceptor complexes (EDA) [1-3] of transition metal cations with organic molecules containing n-bond(s) or free electron pairs (hi, O, S, halogens) may be used for the gas chromatographic separation of these molecules. The column packings containing the transition metals may be termed as superselectivepackings, because a slight difference in the structure of the separated compounds (e.g. cis- and transisomers) can give considerable difference in the retention time representing several minutes The reaction of complex formation should be rapid and reversible In the case of a 1:1 complex formation gas chromatography is convenient for the determination the stability constants of the newly formed adducts The formation of n-complexes with cations of the transition metals is particulary widely applied in gas chromatography. The termal stability of these complexes changes i~ a very broad temperature range depending on the metal and the ligand.complexes together with the temperatures of their chromatographic analysis. As seen chromatography permits as to examine the~ systems at temperatures higher than their thermal stability determined by static methods. The superselective packings can be divided into two group~ 1. Superselective liquid phases in which a salt or met~complex is melted or dissolved in a common liquid phase. 2. Superselective adsorbents in which a transition metal exists in various forms such as a salt or other co~pounds coated on the surface of a support, a porous i~ organic salt, a zeolite with the transition metal cation~ an inorganic oxide, or an inorganic or organometall~polymer. Steric Effect Substitution of bulky alkyl groups at a carbon double bond decrease the stability constants of n-complexes. The steric effect depends on the position of substitution in the following order: 2 > 4/> 3 > 5 >~ 6 [9, 78]. The small steric effect of the substituent in position 3 can be explained by considerable participation of electronic effect which, for alkyl groups has the opposite influence on stability constants than the steric effect. Electronic Effect The choice of the substituents at the double bond can increase or decrease the stability of the complex according to their electronic nature. For example, the substitution of D for H at the double bond increases the stability of the 7rcomplexes and for Rh 2* even bulk substituents increase the stability of complexes formed. This was called an inverse steric effect The electron-withdrawing effect of C1 on the electrons an aromatic ring causes a decrease in the stability constant of the n-complex of a transition metal with chlorobenzene as compared to the same complex with ethylbenzene Strain Effect:- Due to the large strain of the cyclobutene ring its ~r-complexes are less stable than those with five- and six-membered cycloolefms The Hg 2+ cation forms very strong complexes with olef~ and aromatic hydrocarbons. This is the reason why it applied for the selective retention of such compounds fr0~ hydrocarbon mixtures The stability constants of Hg ~+ complexes with molecules of organic compounds containing oxygen have been

Storge Art History Essay Essay

Storge, the Greek word for familial love, is the title of the art exhibition. Consisting of six works of art, of varying mediums, all but one from the modern era, this art show is meant to project love of family, and the feelings it may bring, whether they are joy or anguish. All the pieces in the show are meant to evoke maternal or paternal feelings in the viewers, and when combined, the pieces are meant to show the journey of parenthood. The duality of the show should be clear with the contrast between some of the happier pieces, such as The Bath, by Cassat, or The Cradle, by Morisot, and some of the darker works, like Migrant Mother, by Lange, and the very famous Pieta, by Michelangelo. The exhibition is also supposed to demonstrate the timelessness of storge, that no matter what century it is, feelings of parenthood are always powerful. Each piece will be placed on its own in a large plain room, and the viewers will walk from one room the next in a sort of chronological order, illustrating the journey of a child’s growth, and how it may affect their parents. The first work shown is The Cradle, and was painted in 1872 using oil on canvas, by Impressionist artist, Berthe Morisot. The piece is of Morisot’s sister Edma gazing at her sleeping baby daughter, and is a beautiful depiction of true motherly love. Morisot used her sister Edma as a model in several other works, like Young Woman Seated at a Window, however, the most powerful works, I found, were the depictions of motherhood, of Edma with her children, such as Hide-and-Seek or On the Grass. The Cradle instills a maternal sense in most viewers, which, after closer inspection seems to be due to the way Morisot had positioned her sister. Edma’s hand drawing the curtain over the cradle, partially obscuring the baby from view creates a feeling of intimacy, and shows the traditional protectiveness a mother has for her child. While the colours that Morisot chose create a somewhat somber feeling, the piece isn’t quite sad. It projects a sense of contentment and serenity, especially coming from the mother’s expression. Some have detected a slight sense of longing in the mother’s eyes, possibly wishing to be able to keep her child safe like this forever, but overall, Morisot creates a peaceful atmosphere evoking motherly sensations in the viewers. The Bath (1892), by Mary Cassat, is another oil on canvas Impressionist painting, also depicting a mother and child. The child in this piece is a few years older than the baby in Morisot’s The Cradle, demonstrating the show’s idea of a child’s growth. Some have described Cassat’s series of pieces showing mother and child as â€Å"largely unsentimental†, however, there is an undeniable feeling of closeness between the two figures, a mother and a daughter. The body language of the mother shows tender care for her daughter, as she gently washes her child’s toes during bathtime. The child, mostly naked, sitting on her mother’s lap is a picture of innocence and vulnerability. The mother cradling her child, holding the girl on her lap with an arm around her hip, creates an image of quiet protectiveness similar to The Cradle. The effect of putting The Bath after Morisot’s piece symbolizes the strong love that mother’s have for their children, because they are both pieces that show the strong bond between parent and child. The painting in the next room after The Bath, is The Banjo Lesson, painted using oil on canvas in 1893, by Henry Ossawa Tanner, a prominent African-American Impressionist painter. This piece shows a black father or grandfather with a young boy on his lap, teaching the boy to play the banjo. Compared with the two works that came before it, The Banjo Lesson shows an even closer bond between parent and child. The closeness of the two figures shows a strong familiarity between them, and again, a feeling of intimacy and protectiveness. The child stands between the man’s legs, leaning against his knee and torso, studiously trying to play a banjo, that’s too big for him, emphasizing his youth and frailty. The man, old and weather, intently watches the child’s delicate fingers, while supporting the neck of the instrument. This painting symbolizes the sharing of knowledge between parent and child, which is a big part of the parental journey. Though there are heavy shadows on the figures’ faces, the concentrated expressions are obvious, and despite that Tanner used mostly darker colours for the foreground, the lighter background, suggesting a fireplace off to the side, creates a feeling of physical warmth, combined with the heartwarming feeling the piece brings. The next three pieces of the Storge show shift the feeling from maternal or paternal warmth, to a slightly sadder sort of feeling. Coming after The Banjo Lesson, is a series of black and white photographs, taken in 1936, Nipomo, California, by Dorothea Lange, called Migrant Mother. The photos all show a poor pea picker, Florence Owens Thompson, the mother of seven children, wearing looks of worry and extreme sadness. All the photos in the set are extremely powerful, because of the feeling of desperation and heartache they generate in viewers of the pictures. At the time, Thompson and her kids had been existing off of frozen vegetables from the field and any birds that her children could kill. The children are positioned differently from photograph to photograph, but the expression on the mother’s face remains the same. It is a mixture of different emotions: disappointment, that she was unable to give her children a proper home; deep concentration, trying to find a way to make a better life for her family; serious concern, about how to make ends meet, where their next meal would come from; and tiredness, physically and mentally exhausted. In most pictures, she cradles her infant, while her other children lean on her. The body language of all the figures represents how a parent is a support system for the child, no matter how exhausted they are. The next work in the Storge exhibition is Arrangement in Grey and Black: Portrait of the Painter’s Mother, painted by James McNeill Whistler, in 1871. The oil on canvas, Impressionist piece shows, as the title dictates, the artist’s mother. At first glance, I had assumed, as did many others, that the mother was at her child’s funeral. It is a very somber picture, the woman wearing all black, clearly old, seeming vulnerable and sad. With some research, I learned that is definitely not what happened. Whistler’s mother had, apparently, sat in on for the portrait when the model became sick. It’s interesting how this piece shows a different sort of familial love. Rather than parent to child, it’s child to parent. Whistler managed to really evoke his mother’s Protestant character with the pose, expression, and colours that he used. There is exceptional attention to detail when it comes to his mother’s face, which kind of symbolizes their relationship. He would have to be very close to her to capture her character in his art, and even to physically recreate her face. I also detected a slight feeling of worry on Whistler’s part, with his mother aging. She had been standing at the start of the portrait, but she had to sit down due to her frailty. So while I did detect, after learning of Whistler’s intentions, a feeling of peace and contentment in the painting, I also felt the feeling of sadness that a child has when the realize they don’t have very much time left with their parent. The last piece, though it breaks from the vaguely chronological order of the show, is arguably the most powerful depiction of mother and son, not just in the show, but ever. Michelangelo’s Pieta, carved from Carrara marble, completed in 1499, depicts every parent’s worst nightmare, the death of a child. Mary holds Jesus’ lifeless body on her lap after the Crucifixion, cradling him in the same way she has been shown cradling Jesus as an infant. Her palms are turned upward as if asking why God would take her son from her, especially in such a violent way. Her face, a picture of numbness and vulnerability, combined with the body language of the two figures creates a sense of a very natural relationship, and shows the bond that was shared between Mary and her son. This piece evokes a very strong reaction in all viewers, of despair and empathy. Regardless of religious background, people have been known to break down into tears at the sight of Pieta, struck by what it would feel like to lose a child. Storge is meant to elicit a strong reaction in all viewers, not just parents. The pieces chosen for this exhibit were meant to show the best and worst events that could occur during parenthood, from cradling your toddler, to cradling your slain child. Viewers should go from craving the bond of parent and child at the beginning of the show, to feeling the loss of a child by the end of it. The artists chosen for this were mostly Impressionist, but I find the most powerful pieces, Migrant Mother by Lange and Pieta by Michelangelo, came from opposite ends of the time spectrum. This shows the timelessness of the journey of parenthood.

Summary Response Essay Topics Explained

Summary Response Essay Topics Explained Why Almost Everything You've Learned About Summary Response Essay Topics Is Wrong Regardless of the sort of paper, understanding the prerequisites of the essay underlies the important aspect to a fast and effortless management of your script. References in case you have used other sources in you review you ought to also have a list of references at the close of the review. This kind of essay needs to be written from the very first person standpoint. A response essay enables a learner to answer an idea or information in an official way. Bear in mind, your view is the thing that dictates a response paper. If you're not a speed reader, you're missing out. You are able to also do some investigating to learn more about the points to discuss as a way to present a logical and compelling review. Summary Present an overview of the critical points together with a limited number of examples. To begin with, it's never feasible for anyone else to define one's gender in their opinion. Basically you find out how you would like to proceed imagining the entire process mentally, then you get started working through it. Students lead busy lives and frequently forget about a coming deadline. Dont forget to compose your essay in the very first person because you are discussing your very own personal feelings to a specific matter. A very simple response isn't enough to keep the audience interested. Based on the approach which you will want to pursue, there are particular considerations about how to compose a reaction paper t o a documentary that you ought to make. So think what you find the most fascinating and what has lots of research potential. As the impact of globalization is increasing, English language has turned into the lingua-franca of every individual. Even though the response may start to tackle the assigned task, it features no development. Each paragraph is going to have a topic sentence that is among the reasons to believe the thesis. In a summary, you should paraphrase the principal thoughts of a bit of writing in your paper. Look back over your annotated text and pick out the portions that you want to have in your essay. Developing a summary and response essay can be a difficult undertaking. Before writing the essay, it's important to select an intriguing topic. Don't forget that the essay is dependent on what you think and feel. Now you understand how to compose a response essay! Writing a response essay is quite much like preparing an analytical one, as you are going to analyze the material and provide an explanation to analysis outcomes. Make an outline An outline is a very simple plan showing how you mean to present the review. It is a separate piece of paper, which serves as a plan for you. The way the business management team plays a huge part in consumer behaviour analysis. The War Against Summary Response Essay Topics A summary grid is a beneficial tool for helping students to pull main ideas from a text before organizing them in a bit of writing. Google's objective is to ultimately earn a search engine that will know just what someone wishes to see. So lets have a look at some examples to illustrate what you might have to do in your work. Allow it to be baby-easy to receive your perspective. If you don't understand a word or term it's up you to rectify the circumstance. In any case, your reaction may also make an overall address to the full documentary without picking parts. If you'd like to read not just an example, but an example that's close to your assignment, you can select a topic by typing topic keywords in the very first line. Then, under this issue type choose Critical and pick the proper subject location. Towards the close of the article it will become clear he wants readers to think that it's not a great thing. On the finished part, you may also compare the documentary with others in the exact genre or subject in order to create readers have better comprehension of the review. Unlike the summary it is made up of your opinions in connection with the article being summarized. Unlike the summary, it's composed of YOUR opinions in connection with the article being summarized. You are able to either opt to support the arguments or ideas in the movie, or concentrate on disputing them. You should come up with an idea based on the way in which the documentary touched you. The chosen approach in the Rolling Stones might be criticized for the simple fact that the magazine's focus is mostly depending on the pop-culture. To put it differently, you've got to analyze the chosen topic. So, as much as possible, make certain to restate your ideas and opinion that you've already raised in some sections of your essay. A response essay is intended to describe your side on whether you agree or disagree with a specific topic. Having to compose a response essay usually means that you ought to think of an answer to a book, article, event, etc..

Modernization Theory And Its Impact On The Future Of...

The Constitutional Court holds the power to review legislation that degrades the democratic integrity of the Constitution. It remains crucial that this power rest with an independent governmental branch. The court system itself establishes a functioning society, whose members knows the law and must comply. Those who choose not comply with the law know that the judicial branch will remedy the injustice in society. The future of the judicial branch has a monumental impact on the future of Turkey’s democratic institutions. Turkey’s future remains ambiguous. On an economic perspective, Turkey is booming. It is quickly launching itself into globalism. A growing economy â€Å"during the first six months of 2011 Turkey even vied with China for position as the world’s fastest growing economy. Since 2002 the Turkish economy has nearly tripled in size, experiencing the longest spurt of prosperity in modern Turkish history† (ÇaÇ §aptay, 2014, pp. 17). Diversifying its efforts to bring the nation into the international realm as global player. A prime example of modernization theory, that as countries modernize, streghten middle class values, it becomes inevitable that countries transition away from oppressive regimes to a strong democratic institution. Hindering a politically effective democracy is the current president of Turkey. Increasing tensions and waning legitimacy from its population is showing signs of stress. 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