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Staudinger Synthesis
The Staudinger synthesis, also called the Staudinger ketene-imine cycloaddition, is a chemical synthesis in which an imine 1 reacts with a ketene 2 through a non-photochemical 2+2 cycloaddition to produce a ''β''-lactam 3. The reaction carries particular importance in the synthesis of β-lactam antibiotics. The Staudinger synthesis should not be confused with the Staudinger reaction, a phosphine or phosphite reaction used to reduce azides to amines. Reviews on the mechanism, stereochemistry, and applications of the reaction have been published.Fu, N.; Tidwell, T. T. "Preparation of β-lactams by +2cycloaddition of ketenes and imines" ''Tetrahedron'' 2008, ''64'', 10465-10496. History The reaction was discovered in 1907 by the German chemist Hermann Staudinger. The reaction did not attract interest until the 1940s, when the structure of penicillin was elucidated. The ''β''-lactam moiety of the first synthetic penicillin was constructed using this cycloaddition, and it rema ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Synthesis
As a topic of chemistry, chemical synthesis (or combination) is the artificial execution of chemical reactions to obtain one or several products. This occurs by physical and chemical manipulations usually involving one or more reactions. In modern laboratory uses, the process is reproducible and reliable. A chemical synthesis involves one or more compounds (known as '' reagents'' or ''reactants'') that will experience a transformation when subjected to certain conditions. Various reaction types can be applied to formulate a desired product. This requires mixing the compounds in a reaction vessel, such as a chemical reactor or a simple round-bottom flask. Many reactions require some form of processing (" work-up") or purification procedure to isolate the final product. The amount produced by chemical synthesis is known as the ''reaction yield''. Typically, yields are expressed as a mass in grams (in a laboratory setting) or as a percentage of the total theoretical quantity that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbonyl
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. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rate-determining Step
In chemical kinetics, the overall rate of a reaction is often approximately determined by the slowest step, known as the rate-determining step (RDS or RD-step or r/d step) or rate-limiting step. For a given reaction mechanism, the prediction of the corresponding rate equation (for comparison with the experimental rate law) is often simplified by using this approximation of the rate-determining step. In principle, the time evolution of the reactant and product concentrations can be determined from the set of simultaneous rate equations for the individual steps of the mechanism, one for each step. However, the analytical solution of these differential equations is not always easy, and in some cases numerical integration may even be required. The hypothesis of a single rate-determining step can greatly simplify the mathematics. In the simplest case the initial step is the slowest, and the overall rate is just the rate of the first step. Also, the rate equations for mechanisms with a s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stereochemistry
Stereochemistry, a subdiscipline of chemistry, involves the study of the relative spatial arrangement of atoms that form the structure of molecules and their manipulation. The study of stereochemistry focuses on the relationships between stereoisomers, which by definition have the same molecular formula and sequence of bonded atoms (constitution), but differ in structural formula (the three-dimensional orientations of their atoms in space). For this reason, it is also known as 3D chemistry—the prefix "stereo-" means "three-dimensionality". Stereochemistry spans the entire spectrum of organic, inorganic, biological, physical and especially supramolecular chemistry. Stereochemistry includes methods for determining and describing these relationships; the effect on the physical or biological properties these relationships impart upon the molecules in question, and the manner in which these relationships influence the reactivity of the molecules in question ( dynamic stereochemis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journal Of The American Chemical Society
The ''Journal of the American Chemical Society'' is a weekly peer-reviewed scientific journal that was established in 1879 by the American Chemical Society. The journal has absorbed two other publications in its history, the ''Journal of Analytical and Applied Chemistry'' (July 1893) and the ''American Chemical Journal'' (January 1914). It covers all fields of chemistry. Since 2021, the editor-in-chief is Erick M. Carreira (ETH Zurich). In 2014, the journal moved to a hybrid open access publishing model. Abstracting and indexing The journal is abstracted and indexed in Chemical Abstracts Service, Scopus, EBSCO databases, ProQuest databases, Index Medicus/MEDLINE/PubMed, and the Science Citation Index Expanded. According to the ''Journal Citation Reports'', the journal has a 2021 impact factor of 16.383. Editors-in-chief The following people are or have been editor-in-chief: * 1879–1880 – Hermann Endemann * 1880–1881 – Gideon E. Moore * 1881–1882 – Hermann Endemann ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Torquoselectivity
Torquoselectivity is a special kind of stereoselectivity observed in electrocyclic reactions in organic chemistry, defined as "the preference for inward or outward rotation of substituents in conrotatory or disrotatory electrocyclic reactions." Torquoselectivity is not to be confused with the normal diastereoselectivity seen in pericyclic reactions, as it represents a further level of selectivity beyond the Woodward-Hoffman rules. The name derives from the idea that the substituents in an electrocyclization appear to rotate over the course of the reaction, and thus selection of a single product is equivalent to selection of one direction of rotation (i.e. the direction of torque on the substituents). The concept was originally developed by Kendall N. Houk. For ring closing reactions, it is an example of enantioselectivity, wherein a single enantiomer of a cyclization product is formed from the selective ring closure of the starting material. In a typical electrocyclic ring closi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journal Of Organic Chemistry
''The Journal of Organic Chemistry'', colloquially known as ''JOC'', is a peer-reviewed scientific journal for original contributions of fundamental research in all branches of theory and practice in organic and bioorganic chemistry. It is published by the publishing arm of the American Chemical Society, with 24 issues per year. According to the ''Journal Citation Reports'', the journal had a 2017 impact factor of 4.805 and it is the journal that received the most cites (100,091 in 2017) in the field of organic chemistry. According to Web of Knowledge (and as December 2012), eleven papers from the journal have received more than 1,000 citations, with the most cited paper having received 7,967 citations. The current editor-in-chief is Scott J. Miller from Yale University. Indexing ''J. Org. Chem.'' is currently indexed in: See also *Organic Letters *Organometallics ''Organometallics'' is a biweekly journal published by the American Chemical Society. Its area of focus is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Woodward–Hoffmann Rules
The Woodward–Hoffmann rules (or the pericyclic selection rules), devised by Robert Burns Woodward and Roald Hoffmann, are a set of rules used to rationalize or predict certain aspects of the stereochemistry and activation energy of pericyclic reactions, an important class of reactions in organic chemistry. The rules are best understood in terms of the concept of ''the conservation of orbital symmetry'' using ''orbital correlation diagrams'' (see Section 3 below). The Woodward–Hoffmann rules are a consequence of the changes in electronic structure that occur during a pericyclic reaction and are predicated on the phasing of the interacting molecular orbitals. They are applicable to all classes of pericyclic reactions (and their microscopic reverse 'retro' processes), including (1) electrocyclic reaction, electrocyclizations, (2) cycloadditions, (3) sigmatropic reactions, (4) group transfer reactions, (5) ene reactions, (6) cheletropic reactions, and (7) dyotropic reactions. Due to t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic And Biomolecular Chemistry
''Organic & Biomolecular Chemistry'' is a weekly peer-reviewed scientific journal covering all aspects of organic chemistry, including organic aspects of chemical biology, medicinal chemistry, natural product chemistry, supramolecular chemistry, macromolecular chemistry, theoretical chemistry, and catalysis. It is published by the Royal Society of Chemistry. Its predecessor journals were ''Perkin Transactions I'' and ''Perkin Transactions II''. The Executive Editor is Richard Kelly. Abstracting and indexing The journal is abstracted and indexed in: * Chemical Abstracts Service * Index Medicus/MEDLINE/PubMed * Science Citation Index * Current Contents/Life Sciences * Current Contents/Physical, Chemical & Earth Sciences * Scopus According to the ''Journal Citation Reports'', the journal has a 2016 impact factor of 3.564. See also *''Natural Product Reports'' *''MedChemComm'' * List of scientific journals * List of scientific journals in chemistry References External links ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclic Compounds
A cyclic compound (or ring compound) is a term for a compound in the field of chemistry in which one or more series of atoms in the compound is connected to form a ring. Rings may vary in size from three to many atoms, and include examples where all the atoms are carbon (i.e., are carbocycles), none of the atoms are carbon (inorganic cyclic compounds), or where both carbon and non-carbon atoms are present (heterocyclic compounds). Depending on the ring size, the bond order of the individual links between ring atoms, and their arrangements within the rings, carbocyclic and heterocyclic compounds may be aromatic or non-aromatic; in the latter case, they may vary from being fully saturated to having varying numbers of multiple bonds between the ring atoms. Because of the tremendous diversity allowed, in combination, by the valences of common atoms and their ability to form rings, the number of possible cyclic structures, even of small size (e.g., < 17 total atoms) numbers in the many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
