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Prismane Synthesis
Prismane or 'Ladenburg benzene' is a polycyclic hydrocarbon with the formula C6H6. It is an isomer of benzene, specifically a valence isomer. Prismane is far less stable than benzene. The carbon (and hydrogen) atoms of the prismane molecule are arranged in the shape of a six-atom triangular prism—this compound is the parent and simplest member of the prismanes class of molecules. Albert Ladenburg proposed this structure for the compound now known as benzene. The compound was not synthesized until 1973. History In the mid 19th century, investigators proposed several possible structures for benzene which were consistent with its empirical formula, C6H6, which had been determined by combustion analysis. The first, which was proposed by Kekulé in 1865, later proved to be closest to the true structure of benzene. This structure inspired several others to draw structures that were consistent with benzene's empirical formula; for example, Ladenburg proposed prismane, Dewar pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Royal Society Of Chemistry
The Royal Society of Chemistry (RSC) is a learned society (professional association) in the United Kingdom with the goal of "advancing the chemistry, chemical sciences". It was formed in 1980 from the amalgamation of the Chemical Society, the Royal Institute of Chemistry, the Faraday Society, and the Society for Analytical Chemistry with a new Royal Charter and the dual role of learned society and professional body. At its inception, the Society had a combined membership of 34,000 in the UK and a further 8,000 abroad. The headquarters of the Society are at Burlington House, Piccadilly, London. It also has offices in Thomas Graham House in Cambridge (named after Thomas Graham (chemist), Thomas Graham, the first president of the Chemical Society) where ''RSC Publishing'' is based. The Society has offices in the United States, on the campuses of The University of Pennsylvania and Drexel University, at the University City Science Center in Philadelphia, Pennsylvania, in both Beijing a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dewar Benzene
Dewar benzene (also spelled ''dewarbenzene'') or bicyclo .2.0exa-2,5-diene is a bicyclic isomer of benzene with the molecular formula C6H6. The compound is named after James Dewar who included this structure in a list of possible C6H6 structures in 1869. However, he did not propose it as the structure of benzene, and in fact he supported the correct structure previously proposed by August Kekulé in 1865. Structure and properties Unlike benzene, Dewar benzene is not flat because the carbons where the rings join are bonded to four atoms rather than three. These carbons tend toward tetrahedral geometry, and the two cyclobutene rings make an angle where they are ''cis''- fused to each other. The compound has nevertheless considerable strain energy and reverts to benzene with a chemical half-life of two days. This thermal conversion is relatively slow because it is symmetry forbidden based on orbital symmetry arguments. Synthesis The compound itself was first synthesized in 1962 as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
4-Phenyl-1,2,4-triazole-3,5-dione
4-Phenyl-1,2,4-triazoline-3,5-dione (PTAD) is an azodicarbonyl compound. PTAD is one of the strongest dienophiles and reacts rapidly with dienes in Diels-Alder reactions. The most prominent use of PTAD was the first synthesis of prismane in 1973. Synthesis The compound was first synthesized in 1894 by Johannes Thiele (chemist), Johannes Thiele and O. Stange. The oxidation of 4-Phenylurazol with lead tetroxide in sulfuric acid yielded small quantities of the substance. It took until 1971 when a practical synthesis was published. The synthesis starts from hydrazine and diethyl carbonate. The product of this step is reacted with phenyl isocyanate and subsequently transformed to the 4-Phenylurazol. Cyclization reaction, Cyclization and subsequent oxidation yields PTAD (6). Also ''Organic Syntheses, Coll.'' Vol. 6, p.936 (1988) References {{DEFAULTSORT:Phenyl-1,2,4-triazole-3,5-dione, 4- Triazoles Phenyl compounds ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzvalene
Benzvalene is an organic compound and one of several isomers of benzene. It was first synthesized in 1971 by Thomas J. Katz et al. The 1971 synthesis consisted of treating cyclopentadiene with methyllithium in dimethyl ether and then with dichloromethane and methyllithium in diethyl ether at −45 °C. It can also be formed in low yield (along with fulvene and Dewar benzene) by irradiation of benzene at 237 to 254 nm. The hydrocarbon in solution was described as having an extremely foul odor. Due to the high steric strain present in benzvalene, the pure compound (~71 kcal/mol higher in energy than benzene) easily detonates, for example by scratching. The compound converts to benzene with a chemical half-life of approximately 10 days. This symmetry-forbidden transition is believed to take place through a diradical intermediate. Polybenzvalene Benzvalene can be polymerized in a Ring opening metathesis polymerisation, ROMP process to polybenzvalene. This polymer contains hig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prismane Synthesis
Prismane or 'Ladenburg benzene' is a polycyclic hydrocarbon with the formula C6H6. It is an isomer of benzene, specifically a valence isomer. Prismane is far less stable than benzene. The carbon (and hydrogen) atoms of the prismane molecule are arranged in the shape of a six-atom triangular prism—this compound is the parent and simplest member of the prismanes class of molecules. Albert Ladenburg proposed this structure for the compound now known as benzene. The compound was not synthesized until 1973. History In the mid 19th century, investigators proposed several possible structures for benzene which were consistent with its empirical formula, C6H6, which had been determined by combustion analysis. The first, which was proposed by Kekulé in 1865, later proved to be closest to the true structure of benzene. This structure inspired several others to draw structures that were consistent with benzene's empirical formula; for example, Ladenburg proposed prismane, Dewar pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rearrangement Reaction
In organic chemistry, a rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. Often a substituent moves from one atom to another atom in the same molecule, hence these reactions are usually intramolecular. In the example below, the substituent R moves from carbon atom 1 to carbon atom 2: :\underset\ce\ce\underset\ce\ce Intermolecular rearrangements also take place. A rearrangement is not well represented by simple and discrete electron transfers (represented by curved arrows in organic chemistry texts). The actual mechanism of alkyl groups moving, as in Wagner-Meerwein rearrangement, probably involves transfer of the moving alkyl group fluidly along a bond, not ionic bond-breaking and forming. In pericyclic reactions, explanation by orbital interactions give a better picture than simple discrete electron transfers. It is, nevertheless, possible to draw the curv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methyl
In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many organic compounds. It is a very stable group in most molecules. While the methyl group is usually part of a larger molecule, bounded to the rest of the molecule by a single covalent bond (), it can be found on its own in any of three forms: methanide anion (), methylium cation () or methyl radical (). The anion has eight valence electrons, the radical seven and the cation six. All three forms are highly reactive and rarely observed. Methyl cation, anion, and radical Methyl cation The methylium cation () exists in the gas phase, but is otherwise not encountered. Some compounds are considered to be sources of the cation, and this simplification is used pervasively in organic chemistry. For example, protonation of methanol gives an elect ... [...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] |
Activation Energy
In chemistry and physics, activation energy is the minimum amount of energy that must be provided for compounds to result in a chemical reaction. The activation energy (''E''a) of a reaction is measured in joules per mole (J/mol), kilojoules per mole (kJ/mol) or kilocalories per mole (kcal/mol). Activation energy can be thought of as the magnitude of the potential barrier (sometimes called the energy barrier) separating minima of the potential energy surface pertaining to the initial and final thermodynamic state. For a chemical reaction to proceed at a reasonable rate, the temperature of the system should be high enough such that there exists an appreciable number of molecules with translational energy equal to or greater than the activation energy. The term "activation energy" was introduced in 1889 by the Swedish scientist Svante Arrhenius. Other uses Although less commonly used, activation energy also applies to nuclear reactions and various other physical phenomena. Te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclopropane
Cyclopropane is the cycloalkane with the molecular formula (CH2)3, consisting of three methylene groups (CH2) linked to each other to form a ring. The small size of the ring creates substantial ring strain in the structure. Cyclopropane itself is mainly of theoretical interest but many of its derivatives are of commercial or biological significance. History Cyclopropane was discovered in 1881 by August Freund, who also proposed the correct structure for the substance in his first paper. Freund treated 1,3-dibromopropane with sodium, causing an intramolecular Wurtz reaction leading directly to cyclopropane. The yield of the reaction was improved by Gustavson in 1887 with the use of zinc instead of sodium. Cyclopropane had no commercial application until Henderson and Lucas discovered its anaesthetic properties in 1929; industrial production had begun by 1936. In modern anaesthetic practice, it has been superseded by other agents. Anaesthesia Cyclopropane was introduced into cli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ring Strain
In organic chemistry, ring strain is a type of instability that exists when bonds in a molecule form angles that are abnormal. Strain is most commonly discussed for small rings such as cyclopropanes and cyclobutanes, whose internal angles are substantially smaller than the idealized value of approximately 109°. Because of their high strain, the heat of combustion for these small rings is elevated. Ring strain results from a combination of angle strain, conformational strain or Pitzer strain (torsional eclipsing interactions), and transannular strain, also known as van der Waals strain or Prelog strain. The simplest examples of angle strain are small cycloalkanes such as cyclopropane and cyclobutane. Ring strain energy can be attributed to the energy required for the distortion of bond and bond angles in order to close a ring. Ring strain energy is believed to be the cause of accelerated rates in altering ring reactions. Its interactions with traditional bond energies chan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
