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Dieckman Condensation
The Dieckmann condensation is the intramolecular chemical reaction of diesters with base to give β-keto esters. It is named after the German chemist Walter Dieckmann (1869–1925). The equivalent intermolecular reaction is the Claisen condensation. : Reaction mechanism Deprotonation of an ester at the α-position generates an enolate ion which then undergoes a 5-exo-trig nucleophilic attack to give a cyclic enol. Protonation with a Brønsted-Lowry acid (H3O+ for example) re-forms the β-keto ester. : Due to the steric stability of five- and six-membered rings, these structures will preferentially be formed. 1,6 diesters will form five-membered cyclic β-keto esters, while 1,7 diesters will form six-membered β-keto esters. Further reading *Dieckmann, W. '' Ber.'' 1894, ''27'', 102 & 965 *Dieckmann, W. ''Ber.'' 1900, ''33'', 595 & 2670 *Dieckmann, W. ''Ann.'' 1901, ''317'', 51 & 93 See also * Claisen condensation * Gabriel-Colman rearrangement * Thorpe–Ziegler reaction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Walter Dieckmann
Walter Dieckmann (8 October 1869 – 12 January 1925) was a German chemist. He is the namesake of the Dieckmann condensation, the intramolecular reaction of diesters with base to give β-keto esters. Dieckmann studied at the University of Munich and became assistant of Adolf von Baeyer Johann Friedrich Wilhelm Adolf von Baeyer (; 31 October 1835 – 20 August 1917) was a German chemist who synthesised indigo and developed a nomenclature for cyclic compounds (that was subsequently extended and adopted as part of the IUPAC org .... 1869 births 1925 deaths 20th-century German chemists Academic staff of the Ludwig Maximilian University of Munich BASF people 19th-century German chemists {{Germany-chemist-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intramolecular Reaction
Intramolecular in chemistry describes a process or characteristic limited within the structure of a single molecule, a property or phenomenon limited to the extent of a single molecule. Examples * intramolecular hydride transfer (transfer of a hydride ion from one part to another within the same molecule) * intramolecular hydrogen bond (a hydrogen bond formed between two functional groups of the same molecule) *cyclization of ω-haloalkylamines and alcohols to form the corresponding saturated nitrogen and oxygen heterocycles, respectively (an SN2 reaction within the same molecule) In intramolecular organic reactions, two reaction sites are contained within a single molecule. This creates a very high effective concentration (resulting in high reaction rates), and, therefore, many intramolecular reactions that would not occur as an intermolecular reaction between two compounds take place. Examples of intramolecular reactions are the Smiles rearrangement, the Dieckmann condensation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Reaction
A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the Atomic nucleus, nuclei (no change to the elements present), and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive Chemical element, elements where both electronic and nuclear changes can occur. The substance (or substances) initially involved in a chemical reaction are called reagent, reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more Product (chemistry), products, which usually have properties different from the reactants. Reactions often consist of a sequence o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ester
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides are fatty acid esters of glycerol; they are important in biology, being one of the main classes of lipids and comprising the bulk of animal fats and vegetable oils. Esters typically have a pleasant smell; those of low molecular weight are commonly used as fragrances and are found in essential oils and pheromones. They perform as high-grade solvents for a broad array of plastics, plasticizers, resins, and lacquers, and are one of the largest classes of synthetic lubricants on the commercial market. Polyesters are important plastics, with monomers linked by ester moieties. Phosphoesters form the backbone of DNA molecules. Nitrate esters, such as nitroglycerin, are known for their explosive properties. '' Nomenclature Etymology Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intermolecular
An intermolecular force (IMF) (or secondary force) is the force that mediates interaction between molecules, including the electromagnetic forces of attraction or repulsion which act between atoms and other types of neighbouring particles, e.g. atoms or ions. Intermolecular forces are weak relative to intramolecular forces – the forces which hold a molecule together. For example, the covalent bond, involving sharing electron pairs between atoms, is much stronger than the forces present between neighboring molecules. Both sets of forces are essential parts of force fields frequently used in molecular mechanics. The investigation of intermolecular forces starts from macroscopic observations which indicate the existence and action of forces at a molecular level. These observations include non-ideal-gas thermodynamic behavior reflected by virial coefficients, vapor pressure, viscosity, superficial tension, and absorption data. The first reference to the nature of microscopic forc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Claisen Condensation
The Claisen condensation is a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base, resulting in a β-keto ester or a β-diketone. It is named after Rainer Ludwig Claisen, who first published his work on the reaction in 1887. Requirements At least one of the reagents must be enolizable (have an α-proton and be able to undergo deprotonation to form the enolate anion). There are a number of different combinations of enolizable and nonenolizable carbonyl compounds that form a few different types of Claisen. The base used must not interfere with the reaction by undergoing nucleophilic substitution or addition with a carbonyl carbon. For this reason, the conjugate sodium alkoxide base of the alcohol formed (e.g. sodium ethoxide if ethanol is formed) is often used, since the alkoxide is regenerated. In mixed Claisen condensations, a non-nucleophilic base such as lithium diisopropylamide, or L ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enolate Ion
In organic chemistry, alkenols (shortened to enols) are a type of reactive structure or intermediate in organic chemistry that is represented as an alkene (olefin) with a hydroxyl group attached to one end of the alkene double bond (). The terms ''enol'' and ''alkenol'' are portmanteaus deriving from "-ene"/"alkene" and the "-ol" suffix indicating the hydroxyl group of alcohols, dropping the terminal "-e" of the first term. Generation of enols often involves removal of a hydrogen adjacent (α-) to the carbonyl group—i.e., deprotonation, its removal as a proton, . When this proton is not returned at the end of the stepwise process, the result is an anion termed an enolate (see images at right). The enolate structures shown are schematic; a more modern representation considers the molecular orbitals that are formed and occupied by electrons in the enolate. Similarly, generation of the enol often is accompanied by "trapping" or masking of the hydroxy group as an ether, such as a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baldwin's Rules
Baldwin's rules in organic chemistry are a series of guidelines outlining the relative favorabilities of ring closure reactions in alicyclic compounds. They were first proposed by Jack Baldwin in 1976. Baldwin's rules discuss the relative rates of ring closures of these various types. These terms are not meant to describe the absolute probability that a reaction will or will not take place, rather they are used in a relative sense. A reaction that is disfavoured (slow) does not have a rate that is able to compete effectively with an alternative reaction that is favoured (fast). However, the disfavoured product may be observed, if no alternate reactions are more favoured. The rules classify ring closures in three ways: *the number of atoms in the newly formed ring *into ''exo'' and ''endo'' ring closures, depending whether the bond broken during the ring closure is inside (''endo'') or outside (''exo'') the ring that is being formed *into ''tet'', ''trig'' and ''dig'' geometry of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dieckmann StartAnimGif 1 (1869-1925), German chemist
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Dieckmann is a surname, and may refer to; * August Dieckmann (1912-1943), German colonel * Bärbel Dieckmann (1949- ), German politician * Carolina Dieckmann (1978- ), Brazilian actress * Christina Dieckmann (1977- ), Venezuelan actress * Christoph Dieckmann (beach volleyball) (1976- ), German beach volleyball player * Ed Dieckmann, Netherlands musician * Johannes Dieckmann (1893-1969), East German politician * Katherine Dieckmann, American film director * Markus Dieckmann (1976- ), German beach volleyball player * Walter Dieckmann Walter Dieckmann (8 October 1869 – 12 January 1925) was a German chemist. He is the namesake of the Dieckmann condensation, the intramolecular reaction of diesters with base to give β-keto esters. Dieckmann studied at the University of Muni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
