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Borrowing Hydrogen
Hydrogen auto-transfer, also known as borrowing hydrogen, is the activation of a chemical reaction by temporary transfer of two hydrogen atoms from the reactant to a catalyst and return of those hydrogen atoms back to a reaction intermediate to form the final product. Two major classes of borrowing hydrogen reactions exist: (a) those that result in hydroxyl substitution, and (b) those that result in carbonyl addition. In the former case, alcohol dehydrogenation generates a transient carbonyl compound that is subject to condensation followed by the return of hydrogen. In the latter case, alcohol dehydrogenation is followed by reductive generation of a nucleophile, which triggers carbonyl addition. As borrowing hydrogen processes avoid manipulations otherwise required for discrete alcohol oxidation and the use of stoichiometric organometallic reagents, they typically display high levels of atom-economy and, hence, are viewed as examples of Green chemistry. History The Guerbet react ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydroxyl Substitution
In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy groups. Both the negatively charged anion , called hydroxide, and the neutral radical , known as the hydroxyl radical, consist of an unbonded hydroxy group. According to IUPAC definitions, the term ''hydroxyl'' refers to the hydroxyl radical () only, while the functional group is called a ''hydroxy group''. Properties Water, alcohols, carboxylic acids, and many other hydroxy-containing compounds can be readily deprotonated due to a large difference between the electronegativity of oxygen (3.5) and that of hydrogen (2.1). Hydroxy-containing compounds engage in intermolecular hydrogen bonding increasing the electrostatic attraction between molecules and thus to higher boiling and melting points than found for compounds that lack this func ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Renewable Fuels
Renewable Fuels are fuels produced from renewable resources. Examples include: biofuels (e.g. Vegetable oil used as fuel, ethanol, methanol from clean energy and carbon dioxide or biomass, and biodiesel) and Hydrogen fuel (when produced with renewable processes). This is in contrast to non-renewable fuels such as natural gas, LPG (propane), petroleum and other fossil fuels and nuclear energy. Renewable fuels can include fuels that are synthesized from renewable energy sources, such as wind and solar. Renewable fuels have gained in popularity due to their sustainability, low contributions to the carbon cycle, and in some cases lower amounts of greenhouse gases. The geo-political ramifications of these fuels are also of interest, particularly to industrialized economies which desire independence from Middle Eastern oil. Rationale for renewable fuels The International Energy Agency's ''World Energy Outlook 2006'' concludes that rising oil demand, if left unchecked, would acce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BH Scheme 2
BH, Bh or bh may refer to: Medicine * Bernard-Horner syndrome, a combination of symptoms that arises when a group of nerves known as the sympathetic trunk is damaged * Borderline hypertensive, an American medical classification for cases where a person's blood pressure is elevated above normal, but not to the level considered hypertension * Bronchial hyperresponsiveness, a state characterised by easily triggered bronchospasm * Bundle of His, collection of heart muscle cells specialized for electrical conduction Science and technology * BH register, in computer architectures * Bohrium, symbol Bh, a chemical element * Boron monohydride, chemical formula BH, a chemical compound * Black hole Places * BH postcode area, a region in southern England served by Bournemouth postal sorting office * Bahrain (ISO 3166-1 country code BH) ** .bh, the Internet country code top-level domain for Bahrain * Belize's WMO and obsolete NATO country code digram * Belo Horizonte, the capital of Mina ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Krische Allylation
The Krische allylation involves the enantioselective iridium-catalyzed addition of an allyl group to an aldehyde or an alcohol, resulting in the formation of a secondary homoallylic alcohol. The mechanism of the Krische allylation involves primary alcohol dehydrogenation or, when using aldehyde reactants, hydrogen transfer from 2-propanol. Unlike other allylation methods, the Krische allylation avoids the use of preformed allyl metal reagents and enables the direct conversion of primary alcohols to secondary homoallylic alcohols (precluding alcohol to aldehyde oxidation). Background Enantioselective carbonyl allylations are frequently applied to the synthesis of polyketide natural products. In 1978, Hoffmann reported the first asymmetric carbonyl allylation using a chiral allylmetal reagent, an allylborane derived from camphor. Subsequently, other chiral allylmetal reagents were developed by Kumada, Roush, Brown, Leighton, and others. These methods utilize preformed allyl meta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scheme 1 BH
A scheme is a systematic plan for the implementation of a certain idea. Scheme or schemer may refer to: Arts and entertainment * ''The Scheme'' (TV series), a BBC Scotland documentary series * The Scheme (band), an English pop band * ''The Scheme'', an action role-playing video game for the PC-8801, made by Quest Corporation * Schemer (comics), Richard Fisk, a Marvel Comics villain turned antihero * Horace Schemer, a fictional character in the TV series ''Shining Time Station'' * Schemee, a fictional child character and Schemer's nephew in the TV Series ''Shining Time Station'' * ''Schemers'' (film), a Scottish film Other uses * Classification scheme, eg a thesaurus, a taxonomy, a data model, or an ontology * Scheme (programming language), a minimalist dialect of Lisp * Scheme (mathematics), a concept in algebraic geometry * Scheme (linguistics), a figure of speech that changes a sentence's structure * Scam, an attempt to swindle or cheat people through deception **Get-rich-quick ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dimethyl Sulfate
Dimethyl sulfate (DMS) is a chemical compound with formula (CH3O)2SO2. As the diester of methanol and sulfuric acid, its formula is often written as ( CH3)2 SO4 or Me2SO4, where CH3 or Me is methyl. Me2SO4 is mainly used as a methylating agent in organic synthesis. Me2SO4 is a colourless oily liquid with a slight onion-like odour (although smelling it would represent significant exposure). Like all strong alkylating agents, Me2SO4 is extremely toxic. Its use as a laboratory reagent has been superseded to some extent by methyl triflate, CF3SO3CH3, the methyl ester of trifluoromethanesulfonic acid. History Dimethyl sulfate was discovered in the early 19th century in an impure form. J. P. Claesson later extensively studied its preparation. It was investigated as a candidate for possible use chemical warfare in World War I in 75% to 25% mixture with methyl chlorosulfonate (CH3ClO3S) called "C-stoff" in Germany, or with chlorosulfonic acid called "Rationite" in France. Product ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iodomethane
Iodomethane, also called methyl iodide, and commonly abbreviated "MeI", is the chemical compound with the formula CH3I. It is a dense, colorless, volatile liquid. In terms of chemical structure, it is related to methane by replacement of one hydrogen atom by an atom of iodine. It is naturally emitted by rice plantations in small amounts. It is also produced in vast quantities estimated to be greater than 214,000 tons annually by algae and kelp in the world's temperate oceans, and in lesser amounts on land by terrestrial fungi and bacteria. It is used in organic synthesis as a source of methyl groups. Preparation and handling Iodomethane is formed via the exothermic reaction that occurs when iodine is added to a mixture of methanol with red phosphorus. The iodinating reagent is phosphorus triiodide that is formed ''in situ:'' :3 CH3OH + PI3 → 3 CH3I + H2PO3H Alternatively, it is prepared from the reaction of dimethyl sulfate with potassium iodide in the presence of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AstraZeneca
AstraZeneca plc () is a British-Swedish multinational pharmaceutical and biotechnology company with its headquarters at the Cambridge Biomedical Campus in Cambridge, England. It has a portfolio of products for major diseases in areas including oncology, cardiovascular, gastrointestinal, infection, neuroscience, respiratory, and inflammation. It has been involved in developing the Oxford–AstraZeneca COVID-19 vaccine. The company was founded in 1999 through the merger of the Swedish Astra AB and the British Zeneca Group (itself formed by the demerger of the pharmaceutical operations of Imperial Chemical Industries in 1993). Since the merger it has been among the world's largest pharmaceutical companies and has made numerous corporate acquisitions, including Cambridge Antibody Technology (in 2006), MedImmune (in 2007), Spirogen (in 2013) and Definiens (by MedImmune in 2014). It has its research and development concentrated in three strategic centres: Cambridge, England; ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pfizer
Pfizer Inc. ( ) is an American multinational pharmaceutical and biotechnology corporation headquartered on 42nd Street in Manhattan, New York City. The company was established in 1849 in New York by two German entrepreneurs, Charles Pfizer (1824–1906) and his cousin Charles F. Erhart (1821–1891). Pfizer develops and produces medicines and vaccines for immunology, oncology, cardiology, endocrinology, and neurology. The company has several blockbuster drugs or products that each generate more than billion in annual revenues. In 2020, 52% of the company's revenues came from the United States, 6% came from each of China and Japan, and 36% came from other countries. Pfizer was a component of the Dow Jones Industrial Average stock market index from 2004 to August 2020. The company ranks 64th on the Fortune 500 and 49th on the Forbes Global 2000. History 1849–1950: Early history Pfizer was founded in 1849 by Charles Pfizer and Charles F. Erhart, two cousins who had i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Michael J
Michael may refer to: People * Michael (given name), a given name * Michael (surname), including a list of people with the surname Michael Given name "Michael" * Michael (archangel), ''first'' of God's archangels in the Jewish, Christian and Islamic religions * Michael (bishop elect), English 13th-century Bishop of Hereford elect * Michael (Khoroshy) (1885–1977), cleric of the Ukrainian Orthodox Church of Canada * Michael Donnellan (1915–1985), Irish-born London fashion designer, often referred to simply as "Michael" * Michael (footballer, born 1982), Brazilian footballer * Michael (footballer, born 1983), Brazilian footballer * Michael (footballer, born 1993), Brazilian footballer * Michael (footballer, born February 1996), Brazilian footballer * Michael (footballer, born March 1996), Brazilian footballer * Michael (footballer, born 1999), Brazilian footballer Rulers =Byzantine emperors= *Michael I Rangabe (d. 844), married the daughter of Emperor Nikephoros I * M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guerbet Reaction
The Guerbet reaction, named after Marcel Guerbet (1861–1938), is an organic reaction that converts a primary Alcohol (chemistry), alcohol into its β-alkylated Dimer (chemistry), dimer Alcohol (chemistry), alcohol with loss of one equivalent of water. The process is of interest because it converts simple inexpensive feedstocks into more valuable products. Its main disadvantage is that the reaction produces mixtures. Scope and applications The original 1899 publication concerned the conversion of N-Butanol, ''n''-butanol to 2-ethylhexanol. 2-ethylhexanol is however more easily prepared by alternative methods (from butyraldehyde). Instead, the Guerbet reaction is mainly applied to fatty alcohols to afford oily products, which are called Guerbet alcohols. They are of commercial interest to as components of cosmetics, plasticizers, and related applications. The reaction is conducted in the temperature range 180-360 °C, often in a sealed reactor. The reaction requires alkali me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbonyl Addition
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containing a carbonyl group is often referred to as a carbonyl compound. The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl, e.g. nickel carbonyl). The remainder of this article concerns itself with the organic chemistry definition of carbonyl, where carbon and oxygen share a double bond. Carbonyl compounds In organic chemistry, a carbonyl group characterizes the following types of compounds: Other organic carbonyls are urea and the carbamates, the derivatives of acyl chlorides chloroformates and phosgene, carbonate esters, thioesters, lactones, lactams, hydroxamates, and isocyanates. Examples of inorganic carbonyl compounds are carbon dioxide and carbonyl sulfide. A sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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