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Alkyl Ketene Dimer
Alkyl ketene dimers (AKDs) are a family of organic compounds based on the 4-membered ring system of oxetan-2-one, which is also the central structural element of propiolactone and diketene. Attached to the oxetane ring of technically relevant alkyl ketene dimers there is a C12 – C16 alkyl group in the 3-position and a C13 – C17 alkylidene group in the 4-position. The main application of alkylated ketene dimers is in the sizing of paper and cardboard, as well as in the hydrophobation of cellulose fibers. The products thus modified are distinguished by higher mechanical strengths and less penetration of water, inks or printing inks. AKD's feature hydrophobic alkyl groups extending from a beta-propiolactone ring. A specific example is derived from the dimerization of the ketene of stearic acid. This ketene is generated by pyrolysis of stearoyl chloride. AKD's react with the hydroxyl groups on the cellulose via esterification reaction. The esterification is competitive with hy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ene Reaction
In organic chemistry, the ene reaction (also known as the Alder-ene reaction by its discoverer Kurt Alder in 1943) is a chemical reaction between an alkene with an allylic hydrogen (the ene) and a compound containing a multiple bond (the enophile), in order to form a new σ-bond with migration of the ene double bond and 1,5 hydrogen shift. The product is a substituted alkene with the double bond shifted to the allylic position. This transformation is a group transfer pericyclic reaction, and therefore, usually requires highly activated substrates and/or high temperatures. Nonetheless, the reaction is compatible with a wide variety of functional groups that can be appended to the ene and enophile moieties. Many useful Lewis acid-catalyzed ene reactions have been also developed, which can afford high yields and selectivities at significantly lower temperatures, making the ene reaction a useful C–C forming tool for the synthesis of complex molecules and natural products. Ene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ketene
In organic chemistry, a ketene is an organic compound of the form , where R and R' are two arbitrary monovalent chemical groups (or two separate substitution sites in the same molecule). The name may also refer to the specific compound ethenone , the simplest ketene. Although they are highly useful, most ketenes are unstable. When used as reagents in a chemical procedure, they are typically generated when needed, and consumed as soon as (or while) they are produced. History Ketenes were first studied as a class by Hermann Staudinger before 1905. Ketenes were systematically investigated by Hermann Staudinger in 1905 in the form of diphenylketene (conversion of \alpha-chlorodiphenyl acetyl chloride with zinc). Staudinger was inspired by the first examples of reactive organic intermediates and stable radicals discovered by Moses Gomberg in 1900 (compounds with triphenylmethyl group). Properties Ketenes are highly electrophilic at the carbon atom bonded with the heteroatom, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hermann Staudinger
Hermann Staudinger (; 23 March 1881 – 8 September 1965) was a German organic chemist who demonstrated the existence of macromolecules, which he characterized as polymers. For this work he received the 1953 Nobel Prize in Chemistry. He is also known for his discovery of ketenes and of the Staudinger reaction. Staudinger, together with Leopold Ružička, also elucidated the molecular structures of pyrethrin I and II in the 1920s, enabling the development of pyrethroid insecticides in the 1960s and 1970s. Early work Staudinger was born in 1881 in Worms. Staudinger, who initially wanted to become a botanist, studied chemistry at the University of Halle, at the TH Darmstadt and at the LMU Munich. He received his "Verbandsexamen" (comparable to Master's degree) from TH Darmstadt. After receiving his Ph.D. from the University of Halle in 1903, Staudinger qualified as an academic lecturer at the University of Strasbourg in 1907. It was here that he discovered the ketenes, a family ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alpha And Beta Carbon
In the nomenclature of organic chemistry, a locant is a term to indicate the position of a functional group or substituent within a molecule. Numeric locants The International Union of Pure and Applied Chemistry (IUPAC) recommends the use of numeric prefixes to indicate the position of substituents, generally by identifying the parent hydrocarbon chain and assigning the carbon atoms based on their substituents in order of precedence. For example, there are at least two isomers of the linear form of pentanone, a ketone that contains a chain of exactly five carbon atoms. There is an oxygen atom bonded to one of the middle three carbons (if it were bonded to an end carbon, the molecule would be an aldehyde, not a ketone), but it is not clear where it is located. In this example, the carbon atoms are numbered from one to five, which starts at one end and proceeds sequentially along the chain. Now the position of the oxygen atom can be defined as on carbon atom number two, three or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triethylamine
Triethylamine is the chemical compound with the formula N(CH2CH3)3, commonly abbreviated Et3N. It is also abbreviated TEA, yet this abbreviation must be used carefully to avoid confusion with triethanolamine or tetraethylammonium, for which TEA is also a common abbreviation. It is a colourless volatile liquid with a strong fishy odor reminiscent of ammonia. Like diisopropylethylamine (Hünig's base), triethylamine is commonly employed in organic synthesis, usually as a base. Synthesis and properties Triethylamine is prepared by the alkylation of ammonia with ethanol: :NH3 + 3 C2H5OH → N(C2H5)3 + 3 H2O The pKa of protonated triethylamine is 10.75,David Evans Research Group and it can be used to prepare buffer solutions at that pH. The |
Isobutyryl Chloride
Isobutyryl chloride (2-methylpropanoyl chloride) is the simplest branched-chain acyl chloride. It is found at room temperature as a corrosive, colorless liquid. References Acyl chlorides Reagents for organic chemistry {{Organic-compound-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclobutane
Cyclobutane is a cycloalkane and organic compound with the formula (CH2)4. Cyclobutane is a colourless gas and commercially available as a liquefied gas. Derivatives of cyclobutane are called cyclobutanes. Cyclobutane itself is of no commercial or biological significance, but more complex derivatives are important in biology and biotechnology. Structure The bond angles between carbon atoms are significantly strained and as such have lower bond energies than related linear or unstrained hydrocarbons, e.g. butane or cyclohexane. As such, cyclobutane is unstable above about 500 °C. The four carbon atoms in cyclobutane are not coplanar; instead the ring typically adopts a folded or "puckered" conformation. This implies that the C-C-C angle is less than 90°. One of the carbon atoms makes a 25° angle with the plane formed by the other three carbons. In this way some of the eclipsing interactions are reduced. The conformation is also known as a "butterfly". Equivalent p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tertiary Amines
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group (these may respectively be called alkylamines and arylamines; amines in which both types of substituent are attached to one nitrogen atom may be called alkylarylamines). Important amines include amino acids, biogenic amines, trimethylamine, and aniline; Inorganic derivatives of ammonia are also called amines, such as monochloramine (). The substituent is called an amino group. Compounds with a nitrogen atom attached to a carbonyl group, thus having the structure , are called amides and have different chemical properties from amines. Classification of amines Amines can be classified according to the nature and number of substituents on nitrogen. Aliphatic amines contain only H and alkyl substituents. Aromatic a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
