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In chemistry, an enantiomer – also called optical isomer, antipode, or optical antipode – is one of two stereoisomers that are non-superposable onto their own mirror image. Enantiomers are much like one's right and left hands; without mirroring one of them, hands cannot be superposed onto each other. No amount of reorientation in three spatial dimensions will allow the four unique groups on the chiral carbon to line up exactly. The number of stereoisomers a molecule has can be determined by the number of chiral carbons it has. Stereoisomers include both enantiomers and diastereomers.
In chemistry, a molecule or ion is called chiral if it cannot be superposed on its mirror image by any combination of rotations, translations, and some conformational changes. This geometric property is called chirality. The terms are derived from Ancient Greek χείρ (cheir) 'hand'; which is the canonical example of an object with this property.
Organophosphorus chemistry is the scientific study of the synthesis and properties of organophosphorus compounds, which are organic compounds containing phosphorus. They are used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment. Some organophosphorus compounds are highly effective insecticides, although some are extremely toxic to humans, including sarin and VX nerve agents.
Phosphine oxides are phosphorus compounds with the formula OPX3. When X = alkyl or aryl, these are organophosphine oxides. Triphenylphosphine oxide is an example. An inorganic phosphine oxide is phosphoryl chloride (POCl3).
Organophosphines are organophosphorus compounds with the formula PRnH3−n, where R is an organic substituent. These compounds can be classified according to the value of n: primary phosphines (n = 1), secondary phosphines (n = 2), tertiary phosphines (n = 3). All adopt pyramidal structures. Organophosphines are generally colorless, lipophilic liquids or solids. The parent of the organophosphines is phosphine (PH3).
Chiraphos is a chiral diphosphine employed as a ligand in organometallic chemistry. This bidentate ligand chelates metals via the two phosphine groups. Its name is derived from its description — being both chiral and a phosphine. As a C2-symmetric ligand, chiraphos is available in two enantiomeric forms, S,S and R,R, each with C2 symmetry.
DIPAMP is an organophosphorus compound that is used as a ligand in homogeneous catalysis. It is a white solid that dissolves in organic solvents. Work on this compound by W. S. Knowles was recognized with the Nobel Prize in Chemistry. DIPAMP was the basis for one of the first industrial scale asymmetric hydrogenation, the synthesis of the drug L-DOPA.
Asymmetric hydrogenation is a chemical reaction that adds two atoms of hydrogen to a target (substrate) molecule with three-dimensional spatial selectivity. Critically, this selectivity does not come from the target molecule itself, but from other reagents or catalysts present in the reaction. This allows spatial information to transfer from one molecule to the target, forming the product as a single enantiomer. The chiral information is most commonly contained in a catalyst and, in this case, the information in a single molecule of catalyst may be transferred to many substrate molecules, amplifying the amount of chiral information present. Similar processes occur in nature, where a chiral molecule like an enzyme can catalyse the introduction of a chiral centre to give a product as a single enantiomer, such as amino acids, that a cell needs to function. By imitating this process, chemists can generate many novel synthetic molecules that interact with biological systems in specific ways, leading to new pharmaceutical agents and agrochemicals. The importance of asymmetric hydrogenation in both academia and industry contributed to two of its pioneers — William Standish Knowles and Ryōji Noyori — being awarded one half of the 2001 Nobel Prize in Chemistry.
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In organic chemistry, the Roskamp reaction is a name reaction describing the reaction between α-diazoesters (such as ethyl diazoacetate) and aldehydes to form β-ketoesters, often utilizing various Lewis acids (such as BF3, SnCl2, and GeCl2) as catalysts. The reaction is notable for its mild reaction conditions and selectivity.
A phosphetane is a 4-membered organophosphorus heterocycle. The parent phosphetane molecule, which has the formula C3H7P, is one atom larger than phosphiranes, one smaller than phospholes, and is the heavy-atom analogue of azetidines. The first known phosphetane synthesis was reported in 1957 by Kosolapoff and Struck, but the method was both inefficient and hard to reproduce, with yields rarely exceeding 1%. A far more efficient method was reported in 1962 by McBride, whose method allowed for the first studies into the physical and chemical properties of phosphetanes. Phosphetanes are a well understood class of molecules that have found broad applications as chemical building blocks, reagents for organic/inorganic synthesis, and ligands in coordination chemistry.
P-Chiral phosphines are organophosphorus compounds of the formula PRR′R″, where R, R′, R″ = H, alkyl, aryl, etc. They are a subset of chiral phosphines, a broader class of compounds where the stereogenic center can reside at sites other than phosphorus. P-chirality exploits the high barrier for inversion of phosphines, which ensures that enantiomers of PRR'R" do not racemize readily. The inversion barrier is relatively insensitive to substituents for triorganophosphines. By contrast, most amines of the type NRR′R″ undergo rapid pyramidal inversion.
Vy Maria Dong is a Vietnamese-American Chancellor's Professor of Chemistry at the University of California, Irvine (UCI). Dong works on enantioselective catalysis and natural product synthesis. She received the Royal Society of Chemistry's Merck, Sharp & Dohme Award in 2020, the American Chemical Society's Elias James Corey Award in 2019, and the UCI's Distinguished Alumni Award in 2018.
Marisa C. Kozlowski is an American chemist who is Professor of Organic and Catalysis Chemistry at the University of Pennsylvania. Her research considers asymmetric synthesis and the development of cost effective catalysts. She was elected Fellow of the American Association for the Advancement of Science in 2012 and American Chemical Society in 2013.
T.V. (Babu) RajanBabu is an organic chemist who holds the position of Distinguished Professor of Chemistry in the College of Arts and Sciences at the Ohio State University. His laboratory traditionally focuses on developing transition metal-catalyzed reactions. RajanBabu is known for helping develop the Nugent-RajanBabu reagent, a chemical reagent used in synthetic organic chemistry as a single electron reductant.
References
- ↑ Ohyun Kwon. OCLC 4780088793.
- 1 2 3 4 5 6 7 "Kwon, Ohyun | UCLA Chemistry and Biochemistry". www.chemistry.ucla.edu. Retrieved 2021-06-02.
- ↑ "Directory | UCLA Chemistry and Biochemistry". www.chemistry.ucla.edu. Retrieved 2021-06-02.
- ↑ Wood, John L. (2020-04-14). Organic Syntheses. John Wiley & Sons. ISBN 978-1-119-70776-9.
- ↑ Kwon, Ohyun. "Phosphine-Catalyzed Annulations and Their Applications".
{{cite journal}}: Cite journal requires|journal=(help) - ↑ "Kwon Phosphines: P-Chiral Monodentate Phosphines from Hydroxyproline". Sigma-Aldrich. Retrieved 2021-06-02.
- ↑ "Kwon Chiral Phosphines - Chiral Catalysts, Ligands, and Reagents". Sigma-Aldrich. Retrieved 2021-06-02.
- ↑ "UC CAI Technology Development Award | UCLA Chemistry and Biochemistry". www.chemistry.ucla.edu. Retrieved 2021-06-02.
- ↑ "Kwon group's discovery of new chemical reaction published in Science | UCLA Chemistry and Biochemistry". www.chemistry.ucla.edu. Retrieved 2021-06-02.
- ↑ "2019-2020 Herbert Newby McCoy Award | UCLA Chemistry and Biochemistry". www.chemistry.ucla.edu. Retrieved 2021-06-02.
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