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Cyclooctadecanonaene
Cyclooctadecanonaene or 8nnulene is an organic compound with chemical formula . It belongs to the class of highly conjugated compounds known as annulenes and is aromatic. The usual isomer that 8nnulene refers to is the most stable one, containing six interior hydrogens and twelve exterior ones, with the nine formal double bonds in the ''cis'',''trans'',''trans'',''cis'',''trans'',''trans'',''cis'',''trans'',''trans'' configuration. It is reported to be a red-brown crystalline solid. Aromaticity Notably, 8nnulene is the first annulene after benzene ( nnulene) to be fully aromatic: its π-system contains 4''n'' + 2 electrons (''n'' = 4), and it is large enough to comfortably accommodate six hydrogen atoms in its interior, allowing it to adopt a planar shape, thus satisfying Hückel's rule. The discovery of aromatic stabilization for 8nnulene is historically significant for confirming earlier theoretical predictions based on molecular orbital theory, since simple versions of vale ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aromatic Ring Current
An aromatic ring current is an effect observed in aromatic molecules such as benzene and naphthalene. If a magnetic field is directed perpendicular to the plane of the aromatic system, a ring current is induced in the delocalized π electrons of the aromatic ring. This is a direct consequence of Ampère's law; since the electrons involved are free to circulate, rather than being localized in bonds as they would be in most non-aromatic molecules, they respond much more strongly to the magnetic field. The ring current creates its own magnetic field. Outside the ring, this field is in the same direction as the externally applied magnetic field; inside the ring, the field counteracts the externally applied field. As a result, the net magnetic field outside the ring is greater than the externally applied field alone, and is less inside the ring. Aromatic ring currents are relevant to NMR spectroscopy, as they dramatically influence the chemical shifts of 1H nuclei ("protons") in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eglinton Reaction
The Glaser coupling is a type of coupling reaction. It is by far the oldest acetylenic coupling and is based on cuprous salts like copper(I) chloride or copper(I) bromide and an additional oxidant like oxygen. The base in its original scope is ammonia. The solvent is water or an alcohol. The reaction was first reported by in 1869. He suggested the following process for his way to diphenylbutadiyne: :CuCl + PhC2H + NH3 → PhC2Cu + NH4Cl :2PhC2Cu + O → PhC2C2Ph + Cu2O Modifications Eglinton reaction In the related Eglinton reaction two terminal alkynes are coupled by a copper(II) salt such as cupric acetate. :2R-\!\!-H -> ce\ce] R-\!\!-\!\!-R The oxidative coupling of alkynes has been used to synthesize a number of fungal antibiotics. The stoichiometry is represented by this highly simplified scheme: : Such reactions proceed via metal-alkyne complex, copper(I)-alkyne complexes. This methodology was used in the synthesis of cyclooctadecanonaene. Another example is the synthe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Compound
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 study of the properties, reactions, and syntheses of organic compounds comprise the discipline known as organic chemistry. For historical reasons, a few classes of carbon-containing compounds (e.g., carbonate salts and cyanide salts), along with a few other exceptions (e.g., carbon dioxide, hydrogen cyanide), are not classified as organic compounds and are considered inorganic. Other than those just named, little consensus exists among chemists on precisely which carbon-containing compounds are excluded, making any rigorous definition of an organic compound elusive. Although organic compounds make up only a small percentage of Earth's crust, they are of central importance because all known life is based on organic compounds. Living t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyenes
In organic chemistry, polyenes are poly- unsaturated, organic compounds that contain at least three alternating double () and single () carbon–carbon bonds. These carbon–carbon double bonds interact in a process known as conjugation, resulting in some unusual optical properties. Related to polyenes are dienes, where there are only two alternating double and single bonds. The following polyenes are used as antibiotics for humans: amphotericin B, nystatin, candicidin, pimaricin, methyl partricin, and trichomycin. Optical properties Some polyenes are brightly colored, an otherwise rare property for a hydrocarbon. Normally alkenes absorb in the ultraviolet region of a spectrum, but the absorption energy state of polyenes with numerous conjugated double bonds can be lowered such that they enter the visible region of the spectrum, resulting in compounds which are coloured (because they contain a chromophore). Thus many natural dyes contain linear polyenes. Chemical and electri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, and highly combustible. Hydrogen is the most abundant chemical substance in the universe, constituting roughly 75% of all normal matter.However, most of the universe's mass is not in the form of baryons or chemical elements. See dark matter and dark energy. Stars such as the Sun are mainly composed of hydrogen in the plasma state. Most of the hydrogen on Earth exists in molecular forms such as water and organic compounds. For the most common isotope of hydrogen (symbol 1H) each atom has one proton, one electron, and no neutrons. In the early universe, the formation of protons, the nuclei of hydrogen, occurred during the first second after the Big Bang. The emergence of neutral hydrogen atoms throughout the universe occurred about 370,000 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tert-Butanol
''tert''-Butyl alcohol is the simplest tertiary alcohol, with a formula of (CH3)3COH (sometimes represented as ''t''-BuOH). Its isomers are 1-butanol, isobutanol, and butan-2-ol. ''tert''-Butyl alcohol is a colorless solid, which melts near room temperature and has a camphor-like odor. It is miscible with water, ethanol and diethyl ether. Natural occurrence ''tert''-Butyl alcohol has been identified in beer and chickpeas. It is also found in cassava, which is used as a fermentation ingredient in certain alcoholic beverages. Preparation ''tert''-Butyl alcohol is derived commercially from isobutane as a coproduct of propylene oxide production. It can also be produced by the catalytic hydration of isobutylene, or by a Grignard reaction between acetone and methylmagnesium chloride. Purification cannot be performed by simple distillation due to formation of an azeotrope with water, although initial drying of the solvent containing large amounts of water is performed by adding benz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Potassium Tert-butoxide
Potassium ''tert''-butoxide is the chemical compound with the formula K+(CH3)3CO−. This colourless solid is a strong base (pKa of conjugate acid around 17), which is useful in organic synthesis. It exists as a tetrameric cubane-type cluster. It is often seen written in chemical literature as potassium ''t''-butoxide. The compound is often depicted as a salt, and it often behaves as such, but it is not ionized in solution. Preparation Potassium ''t''-butoxide is commercially available as a solution and as a solid, but it is often generated ''in situ'' for laboratory use because samples are so sensitive and older samples are often of poor quality. It is prepared by the reaction of dry ''tert''-butyl alcohol with potassium metal. The solid is obtained by evaporating these solutions followed by heating the solid. The solid can be purified by sublimation at 220 °C and 1 mmHg. Sublimation can also take place at 140 °C and 0.01 hPa. It is advisable to cover the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isomerization
In chemistry, isomerization or isomerisation is the process in which a molecule, polyatomic ion or molecular fragment is transformed into an isomer with a different chemical structure. Enolization is an example of isomerization, as is tautomerization. When the isomerization occurs intramolecularly it may be called a rearrangement reaction. When the activation energy for the isomerization reaction is sufficiently small, both isomers will exist in a temperature-dependent equilibrium with each other. Many values of the standard free energy difference, \Delta G^\circ, have been calculated, with good agreement between observed and calculated data. Examples and applications Alkanes Skeletal isomerization occurs in the cracking process, used in the petrochemical industry. As well as reducing the average chain length, straight-chain hydrocarbons are converted to branched isomers in the process, as illustrated the following reaction of ''n''-butane to ''i''-butane. :\overset -> \o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deprotonation
Deprotonation (or dehydronation) is the removal (transfer) of a proton (or hydron, or hydrogen cation), (H+) from a Brønsted–Lowry acid in an acid–base reaction.Henry Jakubowski, Biochemistry Online Chapter 2A3, https://employees.csbsju.edu/hjakubowski/classes/ch331/protstructure/PS_2A3_AA_Charges.html, accessed 12/2/2020 The species formed is the conjugate base of that acid. The complementary process, when a proton is added (transferred) to a Brønsted–Lowry base, is protonation (or hydronation). The species formed is the conjugate acid of that base. A species that can either accept or donate a proton is referred to as amphiprotic. An example is the H2O (water) molecule, which can gain a proton to form the hydronium ion, H3O+, or lose a proton, leaving the hydroxide ion, OH−. The relative ability of a molecule to give up a proton is measured by its p''K''a value. A low p''K''a value indicates that the compound is acidic and will easily give up its proton to a base ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid with a distinctive, unpleasant fish-like smell. Pyridine is colorless, but older or impure samples can appear yellow, due to the formation of extended, unsaturated polymeric chains, which show significant electrical conductivity. The pyridine ring occurs in many important compounds, including agrochemicals, pharmaceuticals, and vitamins. Historically, pyridine was produced from coal tar. As of 2016, it is synthesized on the scale of about 20,000 tons per year worldwide. Properties Physical properties The molecular electric dipole moment is 2.2 debyes. Pyridine is diamagnetic and has a diamagnetic susceptibility of −48.7 × 10−6 cm3·mol−1. The standard enthalpy of formation is 100.2 kJ·mol−1 in the liquid phase ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Copper(II) Acetate
Copper(II) acetate, also referred to as cupric acetate, is the chemical compound with the formula Cu(OAc)2 where AcO− is acetate (). The hydrated derivative, Cu2(OAc)4(H2O)2, which contains one molecule of water for each copper atom, is available commercially. Anhydrous copper(II) acetate is a dark green crystalline solid, whereas Cu2(OAc)4(H2O)2 is more bluish-green. Since ancient times, copper acetates of some form have been used as fungicides and green pigments. Today, copper acetates are used as reagents for the synthesis of various inorganic and organic compounds. Copper acetate, like all copper compounds, emits a blue-green glow in a flame. Structure Copper acetate hydrate adopts the paddle wheel structure seen also for related Rh(II) and Cr(II) tetraacetates. One oxygen atom on each acetate is bound to one copper atom at 1.97 Å (197 pm). Completing the coordination sphere are two water ligands, with Cu–O distances of 2.20 Å (220 pm). The t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkyne
\ce \ce Acetylene \ce \ce \ce Propyne \ce \ce \ce \ce 1-Butyne In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and no other functional groups form a homologous series with the general chemical formula . Alkynes are traditionally known as acetylenes, although the name ''acetylene'' also refers specifically to , known formally as ethyne using IUPAC nomenclature. Like other hydrocarbons, alkynes are generally hydrophobic. Structure and bonding In acetylene, the H–C≡C bond angles are 180°. By virtue of this bond angle, alkynes are rod-like. Correspondingly, cyclic alkynes are rare. Benzyne cannot be isolated. The C≡C bond distance of 121 picometers is much shorter than the C=C distance in alkenes (134 pm) or the C–C bond in alkanes (153 pm). : The triple bond is very strong with a bond strength of 839 kJ/mol. The sigma bond contribute ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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