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Superphane
.2.2.2.2.21,2,3,4,5,6)Cyclophane or superphane is a 6-fold bridged cyclophane with all arene positions in the benzene dimer taken up by ethylene spacers. The compound has been of some scientific interest as a model for testing aromaticity and was first synthesised by Virgil Boekelheide in 1979. Superphane is the base compound for a large group of derivatives with structural variations. The analogs with 2 to 5 bridges are also known compounds. The benzene rings have been replaced by other aromatic units, such as those based on ferrocene or stabilized cyclobutadiene. Numerous derivatives are known with variations in the type and length of the bridging units. Synthesis The first synthesis of superphane itself by Boekelheide involved forming pairs of bridging units. At each stage, two ''o''-chloromethyl toluene structures are pyrolyzed to form ''o''-xylylenes, either directly or via benzocyclobutene intermediates. Upon further pyrolysis, these each undergo electrocyclic ring-opening ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superphane Synthesis Boekelheide
[2.2.2.2.2.2](1,2,3,4,5,6)Cyclophane or superphane is a 6-fold bridged cyclophane with all arene positions in the benzene dimer taken up by ethylene spacers. The compound has been of some scientific interest as a model for testing aromaticity and was first synthesised by Virgil Boekelheide in 1979. Superphane is the base compound for a large group of derivatives with structural variations. The analogs with 2 to 5 bridges are also known compounds. The benzene rings have been replaced by other aromatic units, such as those based on ferrocene or stabilized cyclobutadiene. Numerous derivatives are known with variations in the type and length of the bridging units. Synthesis The first synthesis of superphane itself by Boekelheide involved forming pairs of bridging units. At each stage, two ''o''-chloromethyl toluene structures are pyrolysis, pyrolyzed to form ''o''-xylylenes, either directly or via benzocyclobutene intermediates. Upon further pyrolysis, these each undergo electrocyclic r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclophane
In organic chemistry, a cyclophane is a hydrocarbon consisting of an aromatic unit (typically a benzene ring) and a chain that forms a bridge between two non-adjacent positions of the aromatic ring. More complex derivatives with multiple aromatic units and bridges forming cagelike structures are also known. Cyclophanes are well-studied examples of strained organic compounds. Cyclophanes Structures Paracyclophanes adopt the boat conformation normally observed in cyclohexanes. Smaller value of n lead to greater distortions. X-ray crystallography on ' aracyclophane' shows that the aromatic bridgehead carbon atom makes an angle of 20.5° with the plane. The benzyl carbons deviate by another 20.2°. The carbon-to-carbon bond length alternation has increased from 0 for benzene to 39 pm. Despite their distorted structures, cyclophanes retain their aromaticity, as determined by UV-vis spectroscopy. Reactivity With regards to their reactivity, cyclophanes often exhibit diene-like ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virgil Boekelheide
Virgil Boekelheide (28 July 1919 – 24 September 2003) was an American organic chemist and a professor in the department of chemistry at the University of Oregon. He is known for his work on aromatic compounds, particularly cyclophanes, and a name reaction, the Boekelheide reaction, is named after him. Education and academic career Boekelheide was born in Chelsea, South Dakota to a family of German ancestry. He received his bachelor's degree from Dakota Wesleyan University in 1939. He then received his PhD from the University of Minnesota in 1943, where he worked under the supervision of C. Frederick Koelsch. After three years as an instructor at the University of Illinois, he joined the faculty as a professor at the University of Rochester in 1946. He moved to the University of Oregon in 1960 and remained there for the rest of his research career. He retired in 1984. Boekelheide was awarded the Guggenheim Fellowship in 1953 and was an Alexander von Humboldt Fellow, permittin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chlorination Reaction
In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, drugs. This kind of conversion is in fact so common that a comprehensive overview is challenging. This article mainly deals with halogenation using elemental halogens (F2, Cl2, Br2, I2). Halides are also commonly introduced using salts of the halides and halogen acids. Many specialized reagents exist for and introducing halogens into diverse substrates, e.g. thionyl chloride. Organic chemistry Several pathways exist for the halogenation of organic compounds, including free radical halogenation, ketone halogenation, electrophilic halogenation, and halogen addition reaction. The nature of the substrate determines the pathway. The facility of halogenation is influenced by the halogen. Fluorine and chlorine are more electrophilic and are m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrocarbons
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or exemplified by the odors of gasoline and lighter fluid. They occur in a diverse range of molecular structures and phases: they can be gases (such as methane and propane), liquids (such as hexane and benzene), low melting solids (such as paraffin wax and naphthalene) or polymers (such as polyethylene and polystyrene). In the fossil fuel industries, ''hydrocarbon'' refers to the naturally occurring petroleum, natural gas and coal, and to their hydrocarbon derivatives and purified forms. Combustion of hydrocarbons is the main source of the world's energy. Petroleum is the dominant raw-material source for organic commodity chemicals such as solvents and polymers. Most anthropogenic (human-generated) emissions of greenhouse gases are carb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon NMR
Carbon-13 (C13) nuclear magnetic resonance (most commonly known as carbon-13 NMR spectroscopy or 13C NMR spectroscopy or sometimes simply referred to as carbon NMR) is the application of nuclear magnetic resonance (NMR) spectroscopy to carbon. It is analogous to proton NMR ( NMR) and allows the identification of carbon atoms in an organic molecule just as proton NMR identifies hydrogen atoms. 13C NMR detects only the isotope. The main carbon isotope, is not detected. Although much less sensitive than 1H NMR spectroscopy, 13C NMR spectroscopy is widely used for characterizing organic and organometallic compounds. Chemical shifts 13C NMR chemical shifts follow the same principles as those of 1H, although the typical range of chemical shifts is much larger than for 1H (by a factor of about 20). The chemical shift reference standard for 13C is the carbons in tetramethylsilane (TMS), whose chemical shift is considered to be 0.0 ppm. ImageSize = width:540 height:440 AlignBar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proton NMR
Proton nuclear magnetic resonance (proton NMR, hydrogen-1 NMR, or 1H NMR) is the application of nuclear magnetic resonance in NMR spectroscopy with respect to hydrogen-1 nuclei within the molecules of a substance, in order to determine the structure of its molecules. In samples where natural hydrogen (H) is used, practically all the hydrogen consists of the isotope 1H (hydrogen-1; i.e. having a proton for a nucleus). Simple NMR spectra are recorded in solution, and solvent protons must not be allowed to interfere. Deuterated (deuterium = 2H, often symbolized as D) solvents especially for use in NMR are preferred, e.g. deuterated water, D2O, deuterated acetone, (CD3)2CO, deuterated methanol, CD3OD, deuterated dimethyl sulfoxide, (CD3)2SO, and deuterated chloroform, CDCl3. However, a solvent without hydrogen, such as carbon tetrachloride, CCl4 or carbon disulfide, CS2, may also be used. Historically, deuterated solvents were supplied with a small amount (typically 0.1%) of tet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strain Energy
In physics, the elastic potential energy gained by a wire during elongation with a tensile (stretching) force is called strain energy. For Linear elasticity, linearly elastic materials, strain energy is: : U = \frac 1 2 V \sigma \epsilon = \frac 1 2 V E \epsilon^2 = \frac 1 2 \frac V E \sigma^2 where is Stress (mechanics), stress, is Deformation (engineering), strain, is volume, and is Young's modulus: : E = \frac \sigma \epsilon Molecular strain In a molecule, strain energy is released when the constituent atoms are allowed to rearrange themselves in a chemical reaction.''March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure,'' Michael B. Smith & Jerry March, Wiley-Interscience, 5th edition, 2001, The external work done on an elastic member in causing it to distort from its unstressed state is transformed into strain energy which is a form of potential energy. The strain energy in the form of elastic deformation is mostly recoverable in the form of mec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Picometer
The picometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: pm) or picometer (American spelling) is a unit of length in the International System of Units (SI), equal to , or one trillionth of a metre, which is the SI base unit of length. The picometre is one thousand femtometres, one thousandth of a nanometre ( nm), one millionth of a micrometre (also known as a micron), one billionth of a millimetre, and one trillionth of a metre. The symbol μμ was once used for it. It is also one hundredth of an ångström, an internationally known (but non-SI) unit of length. Use The picometre's length is of an order so small that its application is almost entirely confined to particle physics, quantum physics, chemistry and acoustics. Atoms are between 62 and 520 pm in diameter, and the typical length of a carbon–carbon single bond is 154 pm. Smaller units still may be used to describe smaller particles (some of which are t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Symmetry
Molecular symmetry in chemistry describes the symmetry present in molecules and the classification of these molecules according to their symmetry. Molecular symmetry is a fundamental concept in chemistry, as it can be used to predict or explain many of a molecule's chemical properties, such as whether or not it has a dipole moment, as well as its allowed spectroscopic transitions. To do this it is necessary to use group theory. This involves classifying the states of the molecule using the irreducible representations from the character table of the symmetry group of the molecule. Symmetry is useful in the study of molecular orbitals, with applications to the Hückel method, to ligand field theory, and to the Woodward-Hoffmann rules. Many university level textbooks on physical chemistry, quantum chemistry, spectroscopy and inorganic chemistry discuss symmetry. Another framework on a larger scale is the use of crystal systems to describe crystallographic symmetry in bulk materia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Melting Point
The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at a standard pressure such as 1 atmosphere or 100 kPa. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point. Because of the ability of substances to supercool, the freezing point can easily appear to be below its actual value. When the "characteristic freezing point" of a substance is determined, in fact, the actual methodology is almost always "the principle of observing the disappearance rather than the formation of ice, that is, the melting point." Examples For most substances, melting and freezing points are approximately equal. For example, the melting point ''and'' freezing point of mercury is . How ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Formylation Reaction
A formylation reaction in organic chemistry refers to organic reactions in which an organic compound is functionalized with a formyl group (-CH=O). The reaction is a route to aldehydes (''C''-CH=O), formamides (''N''-CH=O), and formate esters (''O''-CH=O). A reagent that delivers the formyl group is called a formylating agent. A particularly important formylation process is hydroformylation which converts alkenes to the homologated aldehyde. The conversion of benzene to benzaldehyde is the basis of the Gattermann–Koch reaction: Aromatic formylation Formylation reactions are a form of electrophilic aromatic substitution and therefore work best when the aromatic starting materials are electron-rich. Phenols are very commonly encountered as they can be readily deprotonated to form phenoxides which are excellent nucleophiles, other electron rich substrates such as mesitylene, pyrrole, or fused aromatic rings can also be expected to react. Benzene will react under aggressive condi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
