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Paal–Knorr Synthesis
The Paal–Knorr Synthesis in organic chemistry is a reaction that generates either furans, pyrroles, or thiophenes from 1,4-diketones. It is a synthetically valuable method for obtaining substituted furans and pyrroles, common structural components of many natural products. It was initially reported independently by German chemists Carl Paal and Ludwig Knorr in 1884 as a method for the preparation of furans, and has been adapted for pyrroles and thiophenes. Although the Paal–Knorr synthesis has seen widespread use, the mechanism wasn't fully understood until it was elucidated by V. Amarnath ''et al.'' in the 1990s. The furan synthesis requires an acid catalyst: : In the pyrrole synthesis a primary amine participates: : and in that of thiophene for instance the compound phosphorus pentasulfide: : Mechanisms Furan synthesis The acid catalyzed furan synthesis proceeds by protonation of one carbonyl which is attacked by the forming enol of the other carbonyl. Dehydration ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ludwig Knorr
Ludwig Knorr (2 December 1859 – 4 June 1921) was a German chemist. Together with Carl Paal, he discovered the Paal–Knorr synthesis, and the Knorr quinoline synthesis and Knorr pyrrole synthesis are also named after him. The synthesis in 1883 of the analgesic drug antipyrine, now called phenazone, was a commercial success. Antipyrine was the first synthetic drug and the most widely used drug until it was replaced by Aspirin in the early 20th century. Early life Ludwig Knorr was born to a wealthy merchant family in 1859. He grew up in the Sabbadini-Knorr company headquarters, located in the Kaufingerstraße in the center of Munich, and in the family house near the Lake Starnberg. After the early death of his father, the education of him and his four brothers lay in the hands of their mother. In 1878 Knorr received his Abitur and started to study chemistry at the University of Munich. In the beginning, he studied under Jacob Volhard; then, after Volhard left for the Universi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thioketone
In organic chemistry, thioketones (; also known as thiones or thiocarbonyls) are organosulfur compounds related to conventional ketones in which the oxygen has been replaced by a sulfur. Instead of a structure of , thioketones have the structure , which is reflected by the prefix "thio-" in the name of the functional group. Unhindered alkylthioketones typically tend to form polymers or rings. Structure and bonding The C=S bond length of thiobenzophenone is 1.63 Å, which is comparable to 1.64 Å, the C=S bond length of thioformaldehyde, measured in the gas phase. Due to steric interactions, the phenyl groups are not coplanar and the dihedral angle SC-CC is 36°. Unhindered dialkylthiones polymerize or oligomerize but thiocamphor is well characterized red solid. Consistent with the double bond rule, most alkyl thioketones are unstable with respect to dimerization.Organosulfur Chemistry I: Topics in Current Chemistry, 1999, Volume 204/1999, 127-181, The energy difference between ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acetal
In organic chemistry, an acetal is a functional group with the connectivity . Here, the R groups can be organic fragments (a carbon atom, with arbitrary other atoms attached to that) or hydrogen, while the R' groups must be organic fragments not hydrogen. The two R' groups can be equivalent to each other (a "symmetric acetal") or not (a "mixed acetal"). Acetals are formed from and convertible to aldehydes or ketones and have the same oxidation state at the central carbon, but have substantially different chemical stability and reactivity as compared to the analogous carbonyl compounds. The central carbon atom has four bonds to it, and is therefore saturated and has tetrahedral geometry. The term ketal is sometimes used to identify structures associated with ketones (both R groups organic fragments rather than hydrogen) rather than aldehydes and, historically, the term acetal was used specifically for the aldehyde-related cases (having at least one hydrogen in place of an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PKF Dione Yne , the deepest natural harbour in Greece
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PKF may refer to: * Pakistan Korfball Federation *PKF, IATA code for Park Falls Municipal Airport, Park Falls, Wisconsin, US * Paul Karl Feyerabend (1924–1994), Austrian-American philosopher *Peace keeping force * Percy Keese Fitzhugh (1876–1950), American author *PKF International, a network of accounting firms *PKF Karate: **Panamerican Karate Federation, governing body of karate in the Americas **Philippine Karatedo Federation, governing body of karate in the Philippines *''Polska Kronika Filmowa'', Polish Film Chronicle, cinema newsreel *Pollock-Krasner Foundation *Porto Koufo Porto Koufo ( el, Πόρτο Κουφό) is the largest natural harbour in Greece (in depth). The harbour was mentioned by the historian Thucydides. German submarines used it during World War II because of its geographical location and direct ac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journal Of The Chemical Society, Chemical Communications
''ChemComm'' (or ''Chemical Communications''), formerly known as ''Journal of the Chemical Society D: Chemical Communications'' (1969–1971), ''Journal of the Chemical Society, Chemical Communications'' (1972–1995), is a peer-reviewed scientific journal published by the Royal Society of Chemistry. It covers all aspects of chemistry. In January 2012, the journal moved to publishing 100 issues per year. The current chair of the Editorial Board is Douglas Stephan (University of Toronto, Canada), while the executive editor is Richard Kelly. Abstracting and indexing The journal is abstracted and indexed in: * Chemical Abstracts * Science Citation Index * Current Contents/Physical, Chemical & Earth Sciences * Scopus * Index Medicus/MEDLINE/PubMed According to the ''Journal Citation Reports'', the journal has a 2021 impact factor of 6.065. See also * ''New Journal of Chemistry'' * ''Chemical Society Reviews'' * ''Chemical Science'' * ''RSC Advances ''RSC Advances'' is an onlin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PK Epoxy Carbonyl
PK or pk may refer to: Arts and entertainment Gaming * Probability of kill (Pk), in computer games, simulations, models, and operations research * '' Disney's PK: Out of the Shadows'', a 2002 video game * Player killing, player versus player conflict in MMORPGs and MUDs Other media * ''PK'' (film), a 2014 Indian film directed by Rajkumar Hirani and starring Aamir Khan * Paperinik, a cartoon character * Peacekeepers (''Farscape''), in the ''Farscape'' television show Organisations * Pakistan International Airlines (IATA airline code) * Polyteknikkojen Kuoro, a Finnish academic male choir * Promise Keepers, a Christian men's organization * Swedish Publicists' Association (Swedish: ), Swedish journalist organization People * P.K (producer), of the South Korean music production duo Future Bounce * P. K. van der Byl (1923–1999), Rhodesian politician * P. K. Subban (born 1989), hockey player * Paul Kalkbrenner (born 1977), electronic musician * Phil Katz (1962–2000), creator of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synthetic Communications
''Synthetic Communications'' is a peer-reviewed scientific journal covering the synthesis of organic compounds In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The s .... Biochemistry journals Publications established in 1971 English-language journals Taylor & Francis academic journals {{chem-journal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MORE Synthesis
Microwave chemistry is the science of applying microwave radiation to chemical reactions. Microwaves act as high frequency electric fields and will generally heat any material containing mobile electric charges, such as polar molecules in a solvent or conducting ions in a solid. Polar solvents are heated as their component molecules are forced to rotate with the field and lose energy in collisions. Semiconducting and conducting samples heat when ions or electrons within them form an electric current and energy is lost due to the electrical resistance of the material. Microwave heating in the laboratory began to gain wide acceptance following papers in 1986, although the use of microwave heating in chemical modification can be traced back to the 1950s. Although occasionally known by such acronyms as ''MAOS'' (microwave-assisted organic synthesis), ''MEC'' (microwave-enhanced chemistry) or ''MORE synthesis'' (microwave-organic reaction enhancement), these acronyms have had little ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The underground mine gas term for foul-smelling hydrogen sulfide-rich gas mixtures is ''stinkdamp''. Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777. The British English spelling of this compound is hydrogen sulphide, a spelling no longer recommended by the Royal Society of Chemistry or the International Union of Pure and Applied Chemistry. Hydrogen sulfide is toxic to humans and most other animals by inhibiting cellular respiration in a manner similar to hydrogen cyanide. When it is inhaled or it or its salts are ingested in high amounts, damage to organs occurs rapidly with symptoms ranging from breathing difficulties to convulsions and death. Despite this, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lawesson's Reagent
Lawesson's reagent (LR) is a chemical compound used in organic synthesis as a thiation agent. Lawesson's reagent was first made popular by Sven-Olov Lawesson, who did not, however, invent it. Lawesson's reagent was first made in 1956 during a systematic study of the reactions of arenes with P4S10. Preparation Lawesson's reagent is commercially available. It can also be conveniently prepared in the laboratory by heating a mixture of anisole with phosphorus pentasulfide until the mixture is clear and no more hydrogen sulfide is formed, then recrystallized from toluene or xylene. Samples give a strong odor of hydrogen sulfide owing to partial hydrolysis. One common and effective method of destroying the foul smelling residues is to use an excess of sodium hypochlorite (chlorine bleach). Mechanism of action Lawesson's reagent has a four membered ring of alternating sulfur and phosphorus atoms. The central phosphorus/sulfur four-membered ring dissociates to form two reactive dithi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anhydrides
An organic acid anhydride is an acid anhydride that is an organic compound. An acid anhydride is a compound that has two acyl groups bonded to the same oxygen atom. A common type of organic acid anhydride is a carboxylic anhydride, where the parent acid is a carboxylic acid, the formula of the anhydride being (RC(O))2O. Symmetrical acid anhydrides of this type are named by replacing the word ''acid'' in the name of the parent carboxylic acid by the word ''anhydride''. Thus, (CH3CO)2O is called ''acetic anhydride.'' Mixed (or unsymmetrical) acid anhydrides, such as acetic formic anhydride (see below), are known, whereby reaction occurs between two different carboxylic acids. Nomenclature of unsymmetrical acid anhydrides list the names of both of the reacted carboxylic acids before the word "anhydride" (for example, the dehydration reaction between benzoic acid and propanoic acid would yield "benzoic propanoic anhydride"). One or both acyl groups of an acid anhydride may also be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphorus Pentoxide
Phosphorus pentoxide is a chemical compound with molecular formula P4 O10 (with its common name derived from its empirical formula, P2O5). This white crystalline solid is the anhydride of phosphoric acid. It is a powerful desiccant and dehydrating agent. Structure Phosphorus pentoxide crystallizes in at least four forms or polymorphs. The most familiar one, a metastable form (shown in the figure), comprises molecules of P4O10. Weak van der Waals forces hold these molecules together in a hexagonal lattice (However, in spite of the high symmetry of the molecules, the crystal packing is not a close packing). The structure of the P4O10 cage is reminiscent of adamantane with ''T''d symmetry point group. It is closely related to the corresponding anhydride of phosphorous acid, P4O6. The latter lacks terminal oxo groups. Its density is 2.30 g/cm3. It boils at 423 °C under atmospheric pressure; if heated more rapidly it can sublimate. This form can be made by condensing the vap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
