|
Dimethylbutadiene
Dimethylbutadiene, formally referred to as 2,3-dimethyl-1,3-butadiene, is an organic compound with the formula (CH3)2C4H4. It is colorless liquid which served an important role in the early history of synthetic rubber. It is now a specialty reagent. Synthesis Dimethylbutadiene is readily prepared by an acid catalyzed dehydration reaction of pinacol: :3 C6H14O2 → C6H10 + 2 C6H12O + 4 H2O The current industrial route involves dimerization of propene followed by dehydrogenation. Applications In 1909, Fritz Hofmann and a team working at Bayer succeeded in polymerizing dimethylbutadiene. It was then called methyl isoprene because it has one more methyl group than isoprene. Their polymer was the first synthetic rubber. The polymer had a number of deficiencies relative to natural rubber. The Bayer synthesis of dimethylbutadiene involved the dehydration of pinacol, as described above.. Reactions Dimethylbutadiene readily undergoes Diels-Alder reactions and reacts faster ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The study of the properties, reactions, and syntheses of organic compounds comprise the discipline known as organic chemistry. For historical reasons, a few classes of carbon-containing compounds (e.g., carbonate salts and cyanide salts), along with a few other exceptions (e.g., carbon dioxide, hydrogen cyanide), are not classified as organic compounds and are considered inorganic. Other than those just named, little consensus exists among chemists on precisely which carbon-containing compounds are excluded, making any rigorous definition of an organic compound elusive. Although organic compounds make up only a small percentage of Earth's crust, they are of central importance because all known life is based on organic compounds. Living t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synthetic Rubber
A synthetic rubber is an artificial elastomer. They are polymers synthesized from petroleum byproducts. About 32-million metric tons of rubbers are produced annually in the United States, and of that amount two thirds are synthetic. Synthetic rubber, just like natural rubber, has many uses in the automotive industry for tires, door and window profiles, Seal (mechanical), seals such as O-rings and gaskets, hoses, Belt (mechanical), belts, Rubber mat, matting, and flooring. They offer a different range of physical and chemical properties, so can improve the reliability of a given product or application. Synthetic rubbers are superior to natural rubbers in two major respects, thermal stability and resistance to oils and related compounds. They are more resistant to oxidizing agents, such as oxygen and ozone which can reduce the life of products like tires. History of synthetic rubber The expanded use of bicycles, and particularly their pneumatic tires, starting in the 1890s, create ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reagent
In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a substance ''consumed'' in the course of a chemical reaction. ''Solvents'', though involved in the reaction mechanism, are usually not called reactants. Similarly, ''catalysts'' are not consumed by the reaction, so they are not reactants. In biochemistry, especially in connection with enzyme-catalyzed reactions, the reactants are commonly called substrates. Definitions Organic chemistry In organic chemistry, the term "reagent" denotes a chemical ingredient (a compound or mixture, typically of inorganic or small organic molecules) introduced to cause the desired transformation of an organic substance. Examples include the Collins reagent, Fenton's reagent, and Grignard reagents. Analytical chemistry In analytical chemistry, a reagent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dehydration Reaction
In chemistry, a dehydration reaction is a chemical reaction that involves the loss of water from the reacting molecule or ion. Dehydration reactions are common processes, the reverse of a hydration reaction. Dehydration reactions in organic chemistry Esterification The classic example of a dehydration reaction is the Fischer esterification, which involves treating a carboxylic acid with an alcohol to give an ester :RCO2H + R′OH RCO2R′ + H2O Often such reactions require the presence of a dehydrating agent, i.e. a substance that reacts with water. Etherification Two monosaccharides, such as glucose and fructose, can be joined together (to form saccharose) using dehydration synthesis. The new molecule, consisting of two monosaccharides, is called a disaccharide. Nitrile formation Nitriles are often prepared by dehydration of primary amides. :RC(O)NH2 → RCN + H2O Ketene formation Ketene is produced by heating acetic acid and trapping the product: :CH3CO2H → CH2=C= ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pinacol
Pinacol is a white solid organic compound. It is a diol that has hydroxyl groups (-OH) on vicinal carbon atoms. Preparation It may be produced by the pinacol coupling reaction from acetone: Reactions As a vicinal-diol, it can rearrange to pinacolone by the pinacol rearrangement, e.g. by heating with sulfuric acid: Pinacol can be used with borane and boron trichloride to produce useful synthetic intermediates such as pinacolborane, bis(pinacolato)diboron,{{OrgSynth , collvol = 10 , collvolpages = 115 , year = 2004 , prep = v77p0176 , title = Bis(pinacolato)diboron , author1 = Tatsuo Ishiyama, author2= Miki Murata, author3=Taka-aki Ahiko, author4-link= Norio Miyaura, author4=Norio Miyaura and pinacolchloroborane. See also * Semipinacol rearrangement The semipinacol rearrangement is a rearrangement reaction in organic chemistry involving a heterosubstituted alcohol of the type R1R2(HO)C–C(X)R3R4. The hetero substituent can be a halogen (Cl, Br, I), a tosylate, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dimer (chemistry)
A dimer () ('' di-'', "two" + ''-mer'', "parts") is an oligomer consisting of two monomers joined by bonds that can be either strong or weak, covalent or intermolecular. Dimers also have significant implications in polymer chemistry, inorganic chemistry, and biochemistry. The term ''homodimer'' is used when the two molecules are identical (e.g. A–A) and ''heterodimer'' when they are not (e.g. A–B). The reverse of dimerization is often called dissociation. When two oppositely charged ions associate into dimers, they are referred to as ''Bjerrum pairs'', after Niels Bjerrum. Noncovalent dimers Anhydrous carboxylic acids form dimers by hydrogen bonding of the acidic hydrogen and the carbonyl oxygen. For example, acetic acid forms a dimer in the gas phase, where the monomer units are held together by hydrogen bonds. Under special conditions, most OH-containing molecules form dimers, e.g. the water dimer. Excimers and exciplexes are excited structures with a short lifetime. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Propene
Propylene, also known as propene, is an unsaturated organic compound with the chemical formula CH3CH=CH2. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas with a faint petroleum-like odor. Production Steam cracking The dominant technology for producing propylene is steam cracking. The same technology is applied to ethane to ethylene. These two conversions are the #2 and #1 processes in the chemical industry, as judged by their scale. In this process, propane undergoes dehydrogenation. The by-product is hydrogen: :CH3CH2CH3 → CH3CH=CH2 + H2 The yield of propene is about 85 m%. By-products are usually used as fuel for the propane dehydrogenation reaction. Steam cracking is one of the most energy-intensive industrial processes. The feedstock is naphtha or propane, especially in the Middle East, where there is an abundance of propane from oil/gas operations. Propene can be separated by fractional distilla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dehydrogenation
In chemistry, dehydrogenation is a chemical reaction that involves the removal of hydrogen, usually from an organic molecule. It is the reverse of hydrogenation. Dehydrogenation is important, both as a useful reaction and a serious problem. At its simplest, it is useful way of converting alkanes, which are relatively inert and thus low-valued, to olefins, which are reactive and thus more valuable. Alkenes are precursors to aldehydes (), alcohols (), polymers, and aromatics. As a problematic reaction, the fouling and inactivation of many catalysts arises via coking, which is the dehydrogenative polymerization of organic substrates. Enzymes that catalyze dehydrogenation are called dehydrogenases. Heterogeneous catalytic routes Styrene Dehydrogenation processes are used extensively to produce aromatics in the petrochemical industry. Such processes are highly endothermic and require temperatures of 500 °C and above. Dehydrogenation also converts saturated fats to unsatura ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fritz Hofmann (chemist)
Fritz Hofmann (Friedrich Carl Albert) (2 November 1866 in Kölleda – 22 October 1956 in Hanover) was a German organic chemist who first synthesized synthetic rubber. Hofmann studied chemistry in Rostock. On September 12, 1909, he filed a patent for the manufacture of the world's first synthetic rubber. Honors *In 1912, Hofmann received the Emil Fischer Hermann Emil Louis Fischer (; 9 October 1852 – 15 July 1919) was a German chemist and 1902 recipient of the Nobel Prize in Chemistry. He discovered the Fischer esterification. He also developed the Fischer projection, a symbolic way of draw ... Medal from the German Chemical Society for his research on synthetic rubber. See also * Sergei Vasiljevich Lebedev References External links * Organic chemists 20th-century German chemists 20th-century German inventors University of Rostock alumni Humboldt University of Berlin alumni Polymer scientists and engineers Commanders Crosses of the Order of Merit of the Fe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isoprene
Isoprene, or 2-methyl-1,3-butadiene, is a common volatile organic compound with the formula CH2=C(CH3)−CH=CH2. In its pure form it is a colorless volatile liquid. Isoprene is an unsaturated hydrocarbon. It is produced by many plants and animals (including humans) and its polymers are the main component of natural rubber. C. G. Williams named the compound in 1860 after obtaining it from thermal decomposition (pyrolysis) of natural rubber; he correctly deduced the empirical formula C5H8. Natural occurrences Isoprene is produced and emitted by many species of trees (major producers are oaks, poplars, eucalyptus, and some legumes). Yearly production of isoprene emissions by vegetation is around 600 million metric tons, half from tropical broadleaf trees and the remainder primarily from shrubs. This is about equivalent to methane emissions and accounts for around one-third of all hydrocarbons released into the atmosphere. In deciduous forests, isoprene makes up approximately 80% o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Rubber
Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and Indonesia are three of the leading rubber producers. Types of polyisoprene that are used as natural rubbers are classified as elastomers. Currently, rubber is harvested mainly in the form of the latex from the rubber tree (''Hevea brasiliensis'') or others. The latex is a sticky, milky and white colloid drawn off by making incisions in the bark and collecting the fluid in vessels in a process called "tapping". The latex then is refined into the rubber that is ready for commercial processing. In major areas, latex is allowed to coagulate in the collection cup. The coagulated lumps are collected and processed into dry forms for sale. Natural rubber is used extensively in many applications and products, either alone or in combination wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
_(cropped).jpg "Click for more on -> Synthetic Rubber")
