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Encyclopedia > Alkyne
The structural formula of 2-butyne, a simple alkyne-containing molecule

Alkynes are hydrocarbons that have at least one triple bond between two carbon atoms, with the formula CnH2n-2. The alkynes are traditionally known as acetylenes or the acetylene series, although the name acetylene is also used to refer specifically to the simplest member of the series, known as ethyne (C2H2) using formal IUPAC nomenclature. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... The structural formula of a chemical compound is a graphical representation of the molecular structure showing how the atoms are arranged. ... Dimethylacetylene (crotonylene or 2-butyne) is an alkyne with chemical formula CH3C≡CCH3. ... In science, a molecule is a group of atoms in a definite arrangement held together by chemical bonds. ... Oil refineries are key to obtaining hydrocarbons; crude oil is processed through several stages to form desirable hydrocarbons, used in fuel and other commercial products. ... Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Standard atomic weight 12. ... The chemical compound acetylene, also called ethyne, was discovered in 1836 by Edmund Davy, in England; its chemical formula is C2H2 and its structure is: Acetylene is a colorless and extremely flammable gas at standard temperature and pressure and has a pleasantly sweet ethereal odor. ... The International Union of Pure and Applied Chemistry (IUPAC) is an international non-governmental organization devoted to the advancement of chemistry. ...

Contents

Chemical properties

Unlike alkanes and to a lesser extent, alkenes, alkynes are unstable and very reactive. Acetylenes are fairly acidic and have pKa values (25) between that of ammonia (35) or ethanol with 16. This acidity is due to the ability for the negative charge in the acetylide conjugate base to be stabilized as a result of the high s character of the sp orbital in which the electron pair resides. Electrons in a s orbital benefit from closer proximity to the positively charged atom nucleus and therefore lower in energy. Chemical structure of methane, the simplest alkane Alkanes are chemical compounds that consists only of the elements carbon (C) and hydrogen (H) (i. ... The chemical structure of ethylene, the simplest alkene. ... The acid dissociation constant (Ka), also known as the acidity constant or the acid-ionization constant, is a specific equilibrium constant for the reaction of an acid with its conjugate base in aqueous solution [1]. // When an acid dissolves in water, it partly dissociates forming hydronium ions and its conjugate... Ammonia is a compound with the formula NH3. ... Grain alcohol redirects here. ... e- redirects here. ...


A terminal alkyne with a strong base such as sodium, sodium amide, n-butyllithium or a Grignard reagent gives the anion of the terminal alkyne (a metal acetylide): It has been suggested that this article or section be merged into base (chemistry). ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Standard atomic weight 22. ... Sodium amide, also called sodamide, is NaNH2. ... An organolithium reagent is a carbon nucleophile similar to a Grignard reagent. ... A Grignard Reagent is an alkyl- or aryl- magnesium halide. ... An anion is an ion with negative charge. ...

2 RC≡CH + 2 Na → 2 RC≡CNa + H2

More generally:

RC≡CH + B → RC≡C + HB+, where B denotes a strong base.

The acetylide anion is synthetically useful because as a strong nucleophile, it can participate in C−C bond forming reactions. In chemistry, a nucleophile (literally nucleus lover) is a reagent which is attracted to centres of positive charge. ...


It is also possible to form copper and silver alkynes, from this group of compounds silver acetylide is an often used example. Silver acetylide is an inorganic chemical compound with the formula Ag2C2, a metal acetylide. ...

See also: Metal acetylide

A metal acetylide is an alkyne that has had a proton (hydrogen) removed from the terminal end by a metal such as sodium or an organolithium. ...

Structure

The carbon atoms in an alkyne bond are sp hybridized: they each have 2 p orbitals and 2 sp hybrid orbitals. Overlap of an sp orbital from each atom forms one sp-sp sigma bond. Each p orbital on one atom overlaps one on the other atom, forming two pi bonds, giving a total of three bonds. The remaining sp orbital on each atom can form a sigma bond to another atom, for example to hydrogen atoms in the parent compound acetylene. The two sp orbitals on an atom are on opposite sides of the atom: in acetylene, the H-C-C bond angles are 180°. Because a total of 6 electrons take part in bonding this triple bond is very strong with a bond strength of 837 kJ/mol. The sigma bond contributes 369 kJ/mol, the first pi bond contributes 268 kJ/mol and the second pi bond is weak with 202 kJ/mol bond strength. The CC bond distance with 121 picometers is also much less than that of the alkene bond which is 134 pm or the alkane bond with 153 pm. In chemistry, hybridisation is the mixing of atomic orbitals to form new orbitals suitable for bonding. ... Electron configuration is the arrangement of electrons in an atom, molecule or other body. ... four sp³ orbitals three sp² orbitals In chemistry, hybridisation or hybridization (see also spelling differences) is the concept of mixing atomic orbitals to form new hybrid orbitals suitable for the qualitative description of atomic bonding properties. ... Electron atomic and molecular orbitals, showing among others the sigma bond of two s-orbitals and a sigma bond of two p-orbitals In chemistry, sigma bonds (σ bonds) are a type of covalent chemical bond. ... Electron atomic and molecular orbitals, showing a Pi-bond at the bottom right of the picture In chemistry, pi bonds (Ï€ bonds) are bonds with a single nodal plane containing the line segment between the two atoms. ... Acetylene (systematic name: ethyne) is the simplest alkyne hydrocarbon, consisting of two hydrogen atoms and two carbon atoms connected by a triple bond. ... Geometry of the water molecule Molecules have fixed equilibrium geometries--bond lengths and angles--that are dictated by the laws of quantum mechanics. ... In chemistry, bond strength is measured between two atoms joined in a chemical bond. ... Picometre (American spelling: picometer) is an SI measure of length that is equal to 10−12 of a metre. ... The chemical structure of ethylene, the simplest alkene. ...


The simplest alkyne is ethyne (acetylene): H-C≡C-H The chemical compound acetylene, also called ethyne, was discovered in 1836 by Edmund Davy, in England; its chemical formula is C2H2 and its structure is: Acetylene is a colorless and extremely flammable gas at standard temperature and pressure and has a pleasantly sweet ethereal odor. ... Acetylene (systematic name: ethyne) is the simplest alkyne hydrocarbon, consisting of two hydrogen atoms and two carbon atoms connected by a triple bond. ...


Terminal and internal alkynes

Terminal alkynes have a hydrogen atom bonded to at least one of the sp hybridized carbons (those involved in the triple bond. An example would be methylacetylene (1-propyne using IUPAC nomenclature). Methylacetylene (propyne) is an alkyne with the chemical formula CH3C≡CH. It is a component of MAPP gas, which is commonly used in gas welding. ...

Internal alkynes have something other than hydrogen attached to the sp hybridized carbons, usually another carbon atom, but could be a heteroatom. A good example is 2-pentyne, in which there is a methyl group on one side of the triple bond and an ethyl group on the other side. Image File history File links No higher resolution available. ...

Image File history File links No higher resolution available. ...

Synthesis

Alkynes are generally prepared by dehydrohalogenation of vicinal alkyl dihalides or the reaction of metal acetylides with primary alkyl halides. In the Fritsch-Buttenberg-Wiechell rearrangement an alkyne is prepared starting from a vinyl bromide. Dehydrohalogenation is an organic chemistry reaction from which an alkene is obtained from an alkyl halide. ... In chemistry vicinal stands for any two functional groups bonded to two adjacent carbon atoms. ... In chemistry, an alkyl halide is an organic molecule of the form R_X, where X is a halide and R contains a carbon atom bonded to other functional groups or hydrogens. ... The Fritsch-Buttenberg-Wiechell rearrangement is a chemical reaction whereby a 1,1-diaryl-2-bromo-alkene rearranges to a 1,2-diaryl-alkyne by reaction with a strong base such as an alkoxide. ... Chemical structure of the vinyl functional group. ...


Alkynes can be prepared from aldehydes using the Corey-Fuchs reaction or the Seyferth-Gilbert homologation. An aldehyde. ... The Corey-Fuchs reaction is a series of chemical reactions designed to transform an aldehyde into an alkyne. ... The Seyferth-Gilbert homologation is a the chemical reaction of an aryl ketone 1 (or aldehyde) with dimethyl (diazomethyl)phosphonate 2 and potassium tert-butoxide to give substituted alkynes 3. ...


Reactions

Alkynes are involved in many organic reactions. Organic reactions are chemical reactions between organic compounds. ...

In organic chemistry, an electrophilic addition reaction is an addition reaction where in chemical compound a pi bond is removed by the creation of two new covalent bonds. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... The chemical structure of ethylene, the simplest alkene. ... Chemical structure of methane, the simplest alkane Alkanes are chemical compounds that consists only of the elements carbon (C) and hydrogen (H) (i. ... The halogens or halogen elements are a series of nonmetal elements from Group 17 (old-style: VII or VIIA; Group 7 IUPAC Style) of the periodic table, comprising fluorine, F, chlorine, Cl, bromine, Br, iodine, I, and astatine, At. ... Hydrogen halides are acids resulting from the chemical reaction of hydrogen with one of the halogen elements (fluorine, chlorine, bromine, iodine), which are found in group VII of the periodic table. ... A vinyl halide in chemistry is any alkene with at least one halide substituent. ... In chemistry, an alkyl halide is an organic molecule of the form R_X, where X is a halide and R contains a carbon atom bonded to other functional groups or hydrogens. ... Carbonyl group In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom : C=O. The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl, e. ... Enol (or, more officially, but less commonly: alkenol) is an alkene with hydroxyl group on one of the carbon atoms of the double bond. ... Hydrolysis is a chemical reaction or process in which a chemical compound reacts with water. ... Phenylacetylene is an alkyne hydrocarbon containing a phenyl group. ... Acetophenone is a crystalline ketone that is used as a solvent for cellulose ethers and esters in the manufacture of alcohol-soluble resins. ... Image File history File links Size of this preview: 800 × 195 pixelsFull resolution (892 × 217 pixel, file size: 4 KB, MIME type: image/png) Alkyne Hydrolysis I, the creator of this work, hereby grant the permission to copy, distribute and/or modify this document under the terms of the GNU... A Cycloaddition is a pericyclic reaction in which the net result is loss of two pi bonds and gain of two sigma bonds. ... The Diels-Alder reaction The Diels-Alder reaction is an organic chemical reaction (specifically, a cycloaddition) between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene system. ... A pyrylium compound is a conjugated 6 membered carbon ring system with one carbon atom replaced by a positively charged oxygen atom forming a salt with a negatively charged counterion [1]. It is the oxygen pendant of benzene and shares with it aromatic properties. ... In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ... The Azide-Alkyne Huisgen Cycloaddition is a 1,3-dipolar cycloaddition between an azide and a terminal or internal alkyne to give a 1,2,3-triazole. ... Triazole refers to either one of a pair of isomeric chemical compounds with molecular formula C2H3N3, having a five-membered ring of two carbon atoms and three nitrogen atoms. ... The Bergman cyclization or Bergman reaction or Bergman cycloaromatization is an organic reaction and more specifically a rearrangement reaction taking place when an enyne is heated in presence of a suitable proton donor (Scheme 1). ... In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ... A alkyne trimerisation reaction is a [2+2+2] cyclization reaction where three alkyne molecules react to form a benzene compound. ... In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ... The chemical structure of ethylene, the simplest alkene. ... Carbon monoxide, with the chemical formula CO, is a colorless, odorless, and tasteless gas. ... The Pauson–Khand reaction or PKR or PK-type reaction is a [2+2+1] cycloaddition between an alkyne, an alkene and carbon monoxide to form a α,β-cyclopentenone . ... The Mortreux system consists of molybdenum hexacarbonyl resorcinol catalyst system. ... The Mortreux system consists of molybdenum hexacarbonyl resorcinol catalyst system. ... An Enyne metathesis is an organic reaction taking place between an alkyne and an alkene with a metal carbene catalyst forming a butadiene. ... In chemistry, nucleophilic substitution is a class of substitution reaction in which an electron-rich nucleophile attacks a molecule and replaces a group or atom, called the leaving group. ... A carbon-carbon bond is a covalent bond between two carbon atoms. ... In organic chemistry, a nucleophilic addition reaction is an addition reaction where in a chemical compound a pi bond is removed by the creation of two new covalent bonds by the addition of a nucleophile. ... A metal acetylide is an alkyne that has had a proton (hydrogen) removed from the terminal end by a metal such as sodium or an organolithium. ... Carbonyl group In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom : C=O. The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl, e. ... An alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. ... Wikibooks has more about this subject: Hydroboration (Organic chemistry) In organic chemistry, the hydroboration-oxidation reaction is a two-step organic chemical reaction that converts an alkene into a neutral alcohol by the net addition of water across the double bond. ... Organoborane or organoboron compounds are chemical compounds comprised of boron and carbon. ... Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colourless in a dilute solution, slightly more viscous than water. ... An aldehyde. ... Ketone group A ketone(key tone) is either the functional group characterized by a carbonyl group (O=C) linked to two other carbon atoms or a chemical compound that contains this functional group. ... Potassium permanganate is the chemical compound KMnO4. ... Structure of a carboxylic acid The 3D structure of the carboxyl group A space-filling model of the carboxyl group Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the formula -C(=O)OH, usually written -COOH or -CO2H. [1] Carboxylic acids are Bronsted... A coupling reaction in organic chemistry is a catch-all for a range of reactions in Organometallic chemistry where two hydrocarbon radicals are coupled with the aid of a metal containing catalyst. ... The Cadiot-Chodkiewicz coupling in organic chemistry is a coupling reaction between a terminal alkyne and a haloalkyne catalyzed by a copper(I) salt such as copper(I) bromide and an amine base [1] [2]. The reaction product is a di-acetylene or di-alkyne. ...

References

  1. ^ Fukuda, Y.; Utimoto, K. "Effective transformation of unactivated alkynes into ketones or acetals with a gold(III) catalyst". J. Org. Chem. 1991, 56, 3729–3731. DOI:10.1021/jo00011a058
  2. ^ Mizushima, E.; Cui, D.-M.; Nath, D. C. D.; Hayashi, T.; Tanaka, M. "Au(I)-Catalyzed hydratation of alkynes: 2,8-nonanedione". Organic Syntheses, Vol. 83, p.55 (2005). Link.

The Journal of Organic Chemistry (abbreviated as ) is a scientific journal for original contributions of fundamental research in organic and bioorganic chemistry. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Organic Syntheses is a scientific journal that Since 1921 has provided the chemistry community with annual collections of detailed and checked procedures for the organic synthesis of organic compounds. ...

See also


  Results from FactBites:
 
The Organometallic HyperTextBook: Alkyne Complexes (759 words)
The bonding of an alkyne (acetylene) to a transition metal complex is similar to that of an alkene complex.
Alkynes tend to be more electropositive and therefore tend to bind more tightly to a transition metal than alkenes.
A number of transition metal alkyne complexes are intermediates in the cyclotrimerization of alkynes to substituted benzenes.
Alkyne - Wikipedia, the free encyclopedia (634 words)
Alkynes are generally prepared by dehydrohalogenation of vicinal alkyl dihalides or the reaction of metal acetylides with primary alkyl halides.
scrambling of alkynes in alkyne metathesis to new alkyne compounds
[2+2+1]cycloaddition of an alkyne, alkene and carbon monoxide in the Pauson–Khand reaction
  More results at FactBites »

 
 

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