A 3D model of ethylene, the simplest alkene.

In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond. ^[1] The simplest acyclic alkenes, with only one double bond and no other functional groups, form a homologous series of hydrocarbons with the general formula C_nH_2n. ^[2] This article needs copy editing for grammar, style, cohesion, tone and/or spelling. ... Image File history File links Download high-resolution version (1100x908, 138 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Ethylene Polyethylene User:Benjah-bmm27/Gallery User:Ben Mills/Gallery ... Image File history File links Download high-resolution version (1100x908, 138 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Ethylene Polyethylene User:Benjah-bmm27/Gallery User:Ben Mills/Gallery ... Ethylene (or IUPAC name ethene) is the chemical compound with the formula C2H4. ... Organic chemistry is a specific discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by other means) of chemical compounds consisting primarily of carbon and hydrogen, which may contain any number of other elements, including nitrogen, oxygen, the halogens as... In chemistry, saturation has four different meanings: In physical chemistry, saturation is the point at which a solution of a substance can dissolve no more of that substance and additional amounts of that substance will appear as a precipitate. ... A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by mass. ... For other uses, see Carbon (disambiguation). ... For other uses, see Carbon (disambiguation). ... 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. ... In organic chemistry, functional groups (or moieties) are specific groups of atoms within molecules, that are responsible for the characteristic chemical reactions of those molecules. ... In chemistry, a homologous series is a series of organic compounds with a similar general formula, possessing similar chemical properties due to the presence of the same functional group, and shows a gradation in physical properties as a result of increase in molecular size and mass (see relative molecular mass). ... A 3-dimensional rendered Ball-and-stick model of the methane molecule. ...

The simplest alkene is ethylene (C₂H₄), which has the International Union of Pure and Applied Chemistry (IUPAC) name ethene. Alkenes are also called olefins (an archaic synonym, widely used in the petrochemical industry). Aromatic compounds are often drawn as cyclic alkenes, but their structure and properties are different and they are not considered to be alkenes.^[2] Ethylene (or IUPAC name ethene) is the chemical compound with the formula C2H4. ... IUPAC logo The International Union of Pure and Applied Chemistry (IUPAC) (Pronounced as eye-you-pack) is an international non-governmental organization established in 1919 devoted to the advancement of chemistry. ... Petrochemicals are chemical products made from raw materials of petroleum (hydrocarbon) origin. ... 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. ...

Structure

Bonding

Ethylene (ethene), showing the pi bond in green.

Like single covalent bonds, double bonds can be described in terms of overlapping atomic orbitals, except that unlike a single bond (which consists of a single sigma bond), a carbon-carbon double bond consists of one sigma bond and one pi bond. This double bond is stronger than a single covalent bond (611 kJ/mol for C=C vs. 347 kJ/mol for C—C) ^[1] and also shorter with an average bond length of 1.33 Angstroms (133 pm). Covalent redirects here. ... 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 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. ... Covalent redirects here. ... The joule (symbol J, also called newton metre, or coulomb volt) is the SI unit of energy and work. ... The mole (symbol: mol) is the SI base unit that measures an amount of substance. ... In molecular geometry, bond length or bond distance is the distance between two bonded atoms in a molecule. ... An angstrom, angström, or Ã¥ngström (symbol Ã…) is a unit of length. ... One picometre is defined as 1x10-12 metres, in standard units. ...

Each carbon of the double bond uses its three sp² hybrid orbitals to form sigma bonds to three atoms. The unhybridized 2p atomic orbitals, which lie perpendicular to the plane created by the axes of the three sp² hybrid orbitals, combine to form the pi bond. This bond lies outside the main C—C axis, with half of the bond on one side and half on the other. In chemistry, hybridisation is the mixing of atomic orbitals to form new orbitals suitable for bonding. ...

Rotation about the carbon-carbon double bond is restricted because it involves breaking the pi bond, which requires a large amount of energy (264 kJ/mol in ethylene). As a consequence substituted alkenes may exist as one of two isomers called a cis isomer and a trans isomer, or alternatively (for more complex alkenes) a Z and a E isomer. For example, in cis-but-2-ene the two methyl substituents face the same side of the double bond and in trans-but-2-ene they face the opposite side; these two isomers are slightly different in their chemical and physical properties. In chemistry, isomers are molecules with the same chemical formula and often with the same kinds of chemical bonds between atoms, but in which the atoms are arranged differently (analogous to a chemical anagram). ... Cis-2-butene Trans-2-butene In chemistry, geometric isomerism or cis-trans isomerism is a form of stereoisomerism and describes the orientation of functional groups within the molecule. ... but-1-ene cis-but-2-ene trans-but-2-ene methylpropene There are four isomers of alkenes which have the chemical formula C4H8. ... In chemistry a methyl-group is a hydrophobic Alkyl functional group which is derived from methane (CH4). ...

It is certainly not impossible to twist a double bond. In fact, a 90° twist requires an energy approximately equal to half the strength of a pi bond. The misalignment of the p orbitals is less than expected because pyramidalization takes place (See: pyramidal alkene). trans-Cyclooctene is a stable strained alkene and the orbital misalignment is only 19° with a dihedral angle of 137° (normal 120°) and a degree of pyramidalization of 18°. This explains the dipole moment of 0.8 D for this compound (cis-isomer 0.4 D) where a value of zero is expected.^[3] The trans isomer of cycloheptene is only stable at low temperatures. Electron atomic and molecular orbitals, showing a Pi-bond at the bottom right of the picture. ... Electron configuration is the arrangement of electrons in an atom, molecule or other body. ... A generic trigonal planar molecule showing ideal bond angle. ... Pyramidal alkenes are alkenes in which the two carbon atoms making up the double bond are not coplanar with their four substituents . ... In Aerospace engineering, the dihedral is the angle that the two wings make with each other. ... The Earths magnetic field, which is approximately a dipole. ... The debye (symbol: D) is a non-SI and non-CGS unit of electrical dipole moment. ... In chemistry, geometric isomerism is a form of stereoisomerism and describes the orientation of functional groups at the ends of a bond around which no rotation is possible. ... Cycloheptene is a 7-membered cycloalkene. ...

Shape

As predicted by the VSEPR model of electron pair repulsion, the molecular geometry of alkenes includes bond angles about each carbon in a double bond of about 120°. The angle may vary because of steric strain introduced by nonbonded interactions created by functional groups attached to the carbons of the double bond. For example, the C-C-C bond angle in propylene is 123.9°. Valence shell electron pair repulsion theory (VSEPR) (1957) is a model in chemistry that aims to generally represent the shapes of individual molecules [1] . To achieve this, it is necessary to construct a valid Lewis structure that shows all of the bonds within the molecule and the locations of lone... For other uses, see Electron (disambiguation). ... Geometry of the water molecule Molecular geometry or molecular structure is the three-dimensional arrangement of the atoms that constitute a molecule, inferred from the spectroscopic studies of the compound. ... 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 van der Waals strain is strain resulting from van der Waals repulsion when two substituents in a molecule approach each other with a distance less than the sum of their van der Waals radii. ... Nonbonded interactions are interactions through electrostatic or van der Waals forces between atoms that are not directly bonded together. ... In organic chemistry, functional groups (or moieties) are specific groups of atoms within molecules, that are responsible for the characteristic chemical reactions of those molecules. ... Propylene, also known by its IUPAC name propene, is an organic compound having the chemical formula C3H6. ...

Physical properties

The physical properties of alkenes are comparable with alkanes. The physical state depends on molecular mass (gases from ethene to butene - liquids from pentene onwards). The simplest alkenes, ethylene, propylene and butylene are gases. Linear alkenes of approximately five to sixteen carbons are liquids, and higher alkenes are waxy solids. Chemical structure of methane, the simplest alkane Alkanes, also known as paraffins, are chemical compounds that consist only of the elements carbon (C) and hydrogen (H) (i. ... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... The molecular mass (abbreviated Mr) of a substance, formerly also called molecular weight and abbreviated as MW, is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ... Ethylene (or IUPAC name ethene) is the chemical compound with the formula C2H4. ... Propylene, also known by its IUPAC name propene, is an organic compound having the chemical formula C3H6. ... Butylene, also known as butene, is the name of the three isomeric hydrocarbon gases with chemical formula C4H8. ...

Chemical properties

Alkenes are relatively stable compounds, but are more reactive than alkanes due to the presence of a carbon-carbon pi-bond. The majority of the reactions of alkenes involve the rupture of this pi bond, forming new single bonds. Chemical structure of methane, the simplest alkane Alkanes, also known as paraffins, are chemical compounds that consist only of the elements carbon (C) and hydrogen (H) (i. ... 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. ...

Alkenes serve as a feedstock for the petrochemical industry because they can participate in a wide variety of reactions. Petrochemicals are chemical products made from raw materials of petroleum (hydrocarbon) origin. ...

Addition reactions

Alkenes react in many addition reactions, which occur by opening up the double-bond. An addition reaction, in chemistry, is in its simplest terms an organic reaction where two or more molecules combine to form a larger one. ...

• Catalytic addition of hydrogen: Catalytic hydrogenation of alkenes produces the corresponding alkanes. The reaction is carried out under pressure in the presence of a metallic catalyst. Common industrial catalysts are based on platinum, nickel or palladium. For laboratory syntheses, Raney nickel is often employed. This is an alloy of nickel and aluminium. An example of this reaction is the catalytic hydrogenation of ethylene to yield ethane:

CH₂=CH₂ + H₂ → CH₃-CH₃

• Electrophilic addition: Most addition reactions to alkenes follow the mechanism of electrophilic addition. An example is the Prins reaction where the electrophile is a carbonyl group.
• Halogenation: Addition of elementary bromine or chlorine to alkenes yields vicinal dibromo- and dichloroalkanes, respectively. The decoloration of a solution of bromine in water is an analytical test for the presence of alkenes:

CH₂=CH₂ + Br₂ → BrCH₂-CH₂Br

It is also used as a quantitive test of unsaturation, expressed as the bromine number of a single compound or mixture. The reaction works because the high electron density at the double bond causes a temporary shift of electrons in the Br-Br bond causing a temporary induced dipole. This makes the Br closest to the double bond slightly positive and therefore an electrophile.

• Hydrohalogenation: Addition of hydrohalic acids such as HCl or HBr to alkenes yields the corresponding haloalkanes.

CH₃-CH=CH₂ + HBr → CH₃-CHBr-CH₂-H

If the two carbon atoms at the double bond are linked to a different number of hydrogen atoms, the halogen is found preferentially at the carbon with fewer hydrogen substituents (Markovnikov's rule).

This is the reaction mechanism for hydrohalogenation:

• Addition of a carbene or carbenoid yields the corresponding cyclopropane.

Catalytic hydrogenation of alkenes produce the corresponding alkanes. ... In chemistry and biology, catalysis (in Greek meaning to annul) is the acceleration of the rate of a chemical reaction by means of a substance, called a catalyst, that is itself unchanged chemically by the overall reaction. ... Chemical structure of methane, the simplest alkane Alkanes, also known as paraffins, are chemical compounds that consist only of the elements carbon (C) and hydrogen (H) (i. ... It has been suggested that this article or section be merged into Catalysis. ... General Name, Symbol, Number platinum, Pt, 78 Chemical series transition metals Group, Period, Block 10, 6, d Appearance grayish white Standard atomic weight 195. ... For other uses, see Nickel (disambiguation). ... For other uses, see Palladium (disambiguation). ... Raney nickel is an amorphous solid composed of finely divided grains of a nickel/aluminium alloy. ... Steel is a metal alloy whose major component is iron, with carbon content between 0. ... For other uses, see Nickel (disambiguation). ... Aluminum redirects here. ... Ethylene (or IUPAC name ethene) is the chemical compound with the formula C2H4. ... This article is about a chemical compound. ... 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. ... 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. ... The Prins reaction is an organic reaction consisting of an electrophilic addition of an aldehyde or ketone to an alkene or alkyne followed by capture of a nucleophile . The outcome of the reaction depends on reaction conditions (scheme 1). ... 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. ... Halogenation is a chemical reaction that replaces a hydrogen atom with a halogen atom. ... Bromo redirects here. ... General Name, symbol, number chlorine, Cl, 17 Chemical series nonmetals Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... In chemistry vicinal stands for any two functional groups bonded to two adjacent carbon atoms. ... This article needs to be wikified. ... Hydrohalogenation is the electrophilic addition of acids like hydrogen chloride or hydrogen bromide to alkenes to yield the corresponding haloalkanes. ... Hydrohalic acid is a group name for the acids of the halogens, which are the aqueous solutions of the hydrogen halides: Fluorine F - hydrofluoric acid: HF Chlorine Cl - hydrochloric acid: HCl Bromine Br - hydrobromic acid: HBr Iodine I - hydroiodic acid: HI As you move further up the list the acids... R-phrases , S-phrases , , , , Flash point non-flammable Supplementary data page Structure and properties n, εr, etc. ... Flash point Non flammable Supplementary data page Structure and properties n, εr, etc. ... Tetrafluoroethane (a haloalkane) is a clear liquid which boils well below room temperature (as seen here) and can be extracted from common canned air canisters by simply inverting them during use. ... In chemistry, Markovnikovs rule is an observation based on Zaitsevs rule. ... Image File history File links Download high resolution version (1000x259, 3 KB) Chemical reaction of an alkene and Hydrogen Bromide. ... In chemistry a carbene is a short-lived and highly reactive organic molecule with a divalent carbon atom with only six valence electrons and the general formula: R1R2C: . The carbon atom is sp2 hybridised with an empty p-orbital extending above and below a plane containing R1 and R2 and... In chemistry a carbenoid is a reactive intermediate that shares reaction characteristics with a carbene. ... Molecule structure formula of cyclopropane Cyclopropane is a cycloalkane molecule with the molecular formula C3H6 consisting of three carbon atoms linked to each other to form a ring, with each carbon atom bearing two hydrogen atoms. ...

Oxidation

Alkenes are oxidized with a large number of oxidizing agents. Organic reductions or organic oxidations or organic redox reactions are redox reactions that take place with organic compounds. ... European Union Chemical hazard symbol for oxidizing agents Dangerous goods label for oxidizing agents Oxidizing agent placard An oxidizing agent (also called an oxidant or oxidizer) is A chemical compound that readily transfers oxygen atoms or A substance that gains electrons in a redox chemical reaction. ...

• In the presence of oxygen, alkenes burn with a bright flame to produce carbon dioxide and water.
• Catalytic oxidation with oxygen or the reaction with percarboxylic acids yields epoxides
• Reaction with ozone in ozonolysis leads to the breaking of the double bond, yielding two aldehydes or ketones

R₁-CH=CH-R₂ + O₃ → R₁-CHO + R₂-CHO + H₂O

This reaction can be used to determine the position of a double bond in an unknown alkene.

• Sharpless bishydroxylation and the Woodward cis-hydroxylation give diols

This article is about the chemical element and its most stable form, or dioxygen. ... Carbon dioxide (chemical formula: ) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... In chemistry and biology, catalysis (in Greek meaning to annul) is the acceleration of the rate of a chemical reaction by means of a substance, called a catalyst, that is itself unchanged chemically by the overall reaction. ... In chemistry, carboxylic acids (also called alkanoic acids) are organic acids characterized by the presence of a carboxyl group. ... An epoxide is a cyclic ether with only three ring atoms. ... In ozonolysis ozone cleaves an alkene into carbonyl compounds. ... An aldehyde. ... Ketone group A ketone (pronounced as 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. ... Sharpless bishydroxylation or asymmetric dihydroxylation (AD) is a chemical reaction of an alkene with osmium tetroxide to form a diol (dialcohol). ... The Woodward cis-hydroxylation is the chemical reaction of alkenes with iodine and silver acetate in wet acetic acid to form cis-diols. ... A diol is a chemical compound containing two hydroxyl groups (-OH groups). ...

Polymerization

Polymerization of alkenes is an economically important reaction which yields polymers of high industrial value, such as the plastics polyethylene and polypropylene. Polymerization can either proceed via a free-radical or an ionic mechanism. An example of alkene polymerisation, in which each Styrene monomer units double bond reforms as a single bond with another styrene monomer and forms polystyrene. ... A polymer (from Greek: πολυ, polu, many; and μέρος, meros, part) is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ... This article does not cite any references or sources. ... Polypropylene lid of a Tic Tacs box, with a living hinge and the resin identification code under its flap Micrograph of polypropylene Polypropylene or polypropene (PP) is a thermoplastic polymer, made by the chemical industry and used in a wide variety of applications, including food packaging, ropes, textiles, stationery, plastic... In chemistry, radicals (often referred to as free radicals) are atomic or molecular species with unpaired electrons on an otherwise open shell configuration. ...

Synthesis

Industrial methods

The most common industrial synthesis of alkenes is based on cracking of petroleum. Large alkanes are broken apart at high temperatures, often in the presence of a zeolite catalyst, to give alkenes and smaller alkanes, and the mixture of products is then separated by fractional distillation. This is mainly used for the manufacture of small alkenes (up to six carbons).^[1] Factory of Shukhov cracking process, Baku, USSR, 1934 In petroleum geology and chemistry, cracking is the process whereby complex organic molecules such as kerogens or heavy hydrocarbons are broken down into simpler molecules (e. ... Petro redirects here. ... Zeolite The micro-porous molecular structure of a zeolite, ZSM-5 Zeolites (Greek, zein, to boil; lithos, a stone) are minerals that have a micro-porous structure. ...

Related to this is catalytic dehydrogenation, where an alkane loses hydrogen at high temperatures to produce a corresponding alkene. ^[1] This is the reverse of the catalytic hydrogenation of alkenes. Hydrogenation is a chemical reaction in which unsaturated bonds between carbon atoms are reduced by attachment of a hydrogen atom to each carbon. ...

Both of these processes are endothermic, but they are driven towards the alkene at high temperatures by entropy (the TΔS portion of the equation ΔG = ΔH – TΔS dominates for high T). For other uses, see: information entropy (in information theory) and entropy (disambiguation). ...

Catalytic synthesis of higher α-alkenes (of the type RCH=CH₂) can also be achieved by a reaction of ethylene with the organometallic compound triethylaluminium in the presence of nickel, cobalt or platinum. In chemistry and biology, catalysis (in Greek meaning to annul) is the acceleration of the rate of a chemical reaction by means of a substance, called a catalyst, that is itself unchanged chemically by the overall reaction. ... An organometallic compound is partially characterized by the presence of one or more metal-carbon bonds, in which the carbon involved would, apart from the metal-carbon bond, be otherwise considered a part of an organic compound. ... Triethylaluminum or TEA ( (CH3CH2)3Al ) is a volatile organometallic compound which is used in various chemical processing and as an ignitor for jet and rocket engines. ... For other uses, see Nickel (disambiguation). ... For other uses, see Cobalt (disambiguation). ... General Name, Symbol, Number platinum, Pt, 78 Chemical series transition metals Group, Period, Block 10, 6, d Appearance grayish white Standard atomic weight 195. ...

Elimination reactions

One of the principal methods for alkene synthesis in the laboratory is the elimination of alkyl halides, alcohols and similar compounds. Most common is the -elimination via the E2 or E1 mechanism, ^[4] but -eliminations are also known. An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one or two-step mechanism. ...

The E2 mechanism provides a more reliable -elimination method than E1 for most alkene syntheses. Most E2 eliminations start with an alkyl halide or alkyl sulfonate ester (such as a tosylate or triflate). When an alkyl halide is used, the reaction is called a dehydrohalogenation. For unsymmetrical products the more substituted alkenes (those with fewer hydrogens attached to the C=C) tend to predominate (see Saytzeff's rule).Two common methods of elimination reactions are dehydrohalogenation of alkyl halides and dehydration of alcohols. A typical example is shown below; note that the H that leaves must be anti to the leaving group, even though this leads to the less stable Z-isomer.^[5] The tosylate group with a generic R group attached (where R can be anything, typically a carbon). ... Triflate, more formally known as trifluoromethanesulfonate, is a functional group with the formula CF3SO3-. The triflate group is often represented by -OTf, as opposed to -Tf. ... Dehydrohalogenation is an organic chemistry reaction from which an alkene is obtained from an alkyl halide. ... Zaitsevs rule or Saytzeffs rule named after A. N. Zaitsev is a rule in chemistry that states: If more than one alkene can be formed by an elimination reaction, the more stable alkene is the major product. ...

Alkenes can be synthesized from alcohols via dehydration, in which case water is lost via the E1 mechanism. For example, the dehydration of ethanol produces ethene: This article does not cite any references or sources. ... In chemistry, a dehydration reaction is a chemical reaction that involves the loss of water from the reacting molecule. ... Grain alcohol redirects here. ...

CH₃CH₂OH + H₂SO₄ → H₂C=CH₂ + H₃O⁺ + HSO₄⁻

An alcohol may also be converted to a better leaving group (e.g., xanthate), so as to allow a milder syn-elimination such as the Chugaev elimination and the Grieco elimination. Related reactions include eliminations by β-haloethers (the Boord olefin synthesis) and esters (ester pyrolysis). Grain alcohol redirects here. ... Sulfuric acid, (also known as sulphuric acid) H2SO4, is a strong mineral acid. ... Ethylene or ethene is the simplest alkene hydrocarbon, consisting of two carbon atoms and four hydrogens. ... Xanthates are the salts of xanthic acid, C2H5OCS2H. Many xanthates have a yellow colour, which gives the compound its name (Greek xanthos means yellow). ... The Chugaev elimination is a chemical reaction that involves the elimination of water from primary alcohols to produce terminal alkenes. ... The Grieco elimination is an organic reaction describing the elimination reaction of an aliphatic primary alcohol through a selenide to a terminal alkene . ... The Boord olefin synthesis is an organic reaction forming alkenes from ethers carrying a halogen atom 2 carbons removed from the oxygen atom (β-halo-ethers) catalyzed by a metal such as magnesium or zinc. ... Ester pyrolysis in organic chemistry is a vacuum pyrolysis reaction converting esters containing a β-hydrogen atom into the corresponding carboxylic acid and the alkene. ...

Alkenes can be prepared indirectly from alkyl amines. The amine or ammonia is not a suitable leaving group, so the amine is first either alkylated (as in the Hofmann elimination) or oxidized to an amine oxide (the Cope reaction) to render a smooth elimination possible. Hofmann elimination is unusual in that the less substituted (non-Saytseff) alkene is usually the major product. The Cope reaction is a syn-elimination that occurs at or below 150 °C, for example:^[6] The general structure of an amine Amines are organic compounds and a type of functional group that contain nitrogen as the key atom. ... Alkylation is the transfer of an alkyl group from one molecule to another. ... Hofmann elimination provides the dealkylation of quaternary ammonium salts to tertiary amines due to the scheme: quaternary ammonium salt via 1. ... An amine oxide, also known as amine-N-oxide and N-oxide, is a chemical compound that contains the functional group R3N+-O− (sometimes written as R3N=O or R3N→O). ... It has been suggested that this article or section be merged into Cope rearrangement. ... Zaitsevs rule or Saytzeffs rule named after A. N. Zaitsev is a rule in chemistry that states: If more than one alkene can be formed by an elimination reaction, the more stable alkene is the major product. ...

Alkenes are generated from α-halo sulfones in the Ramberg-Bäcklund reaction, via a three-membered ring sulfone intermediate. A sulfone is a chemical compound containing a sulfonyl functional group attached to two carbon atoms. ... The Ramberg-Bäcklund Reaction is an organic reaction converting a α-halo sulfone into an alkene in presence of a base with extrusion of sulfur dioxide . ...

Synthesis from carbonyl compounds

Another important method for alkene synthesis involves construction of a new carbon-carbon double bond by coupling of a carbonyl compound (such as an aldehyde or ketone) to a carbanion equivalent. Such reactions are sometimes called olefinations. The most well-known of these methods is the Wittig reaction, but other related methods are known. An aldehyde. ... Ketone group A ketone (pronounced as 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. ... A carbanion is an anion in which carbon has an unshared pair of electrons and bears a negative charge usually with three substituents for a total of eight valence electrons. ...

The Wittig reaction involves reaction of an aldehyde or ketone with a Wittig reagent (or phosphorane) of the type Ph₃P=CHR to produce an alkene and Ph₃P=O. The Wittig reagent is itself prepared easily from triphenylphosphine and an alkyl halide. The reaction is quite general and many functional groups are tolerated, even esters, as in this example:^[7] The Wittig reaction is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide (often called a Wittig reagent) to give an alkene and triphenylphosphine oxide. ... Triphenylphosphine oxide usually appears as white crystals. ... Triphenylphosphine (in Europe: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 - often abbreviated to PPh3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. ...

Related to the Wittig reaction is the Peterson olefination. This uses a less accessible silicon-based reagent in place of the phosphorane, but it allows for the selection of E or Z products. If an E-product is desired, another alternative is the Julia olefination, which uses the carbanion generated from a phenyl sulfone. The Takai olefination based on an organochromium intermediate also delivers E-products. A titanium compound, Tebbe's reagent, is useful for the synthesis of methylene compounds; in this case, even esters and amides react. The Peterson olefination (also called the Peterson reaction) is the chemical reaction of α-silyl carbanions 1 with ketones (or aldehydes) to form a β-hydroxysilane 2 which eliminates to form alkenes 3. ... The Julia olefination (also known as the Julia–Lythgoe olefination) is the chemical reaction of phenyl sulfones (1) with aldehydes (or ketones) to give alkenes (3) after alcohol functionalization and reductive elimination using sodium amalgam or SmI2. ... In chemistry, the phenyl group or phenyl ring (often abbreviated as -Ph) is the functional group with the formula -C6H5 Picture where the six carbon atoms are arranged in a cyclic manner. ... A sulfone is a chemical compound containing a sulfonyl functional group attached to two carbon atoms. ... The Tebbe reagent is (C5H5)2TiCH2ClAl(CH3)2. ...

A pair of carbonyl compounds can also be reductively coupled together (with reduction) to generate an alkene. Symmetrical alkenes can be prepared from a single aldehyde or ketone coupling with itself, using Ti metal reduction (the McMurry reaction). If two different ketones are to be coupled, a more complex, indirect method such as the Barton-Kellogg reaction may be used. The McMurry reaction of benzophenone The McMurry reaction is an organic reaction in which two ketone or aldehyde groups are coupled to an alkene in the presence of a titanium chloride compound such as titanium(III) chloride and a reducing agent . ... The Barton-Kellogg reaction is a coupling reaction between a ketone and a thioketone through a diazo intermediate forming an alkene . This reaction has been pioneered by Hermann Staudinger and therefore the reaction also goes by the name Staudinger type diazo-thioketone coupling. ...

A single ketone can also be converted to the corresponding alkene via its tosylhydrazone, using sodium methoxide (the Bamford-Stevens reaction) or an alkyllithium (the Shapiro reaction). An alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. ... The Bamford-Stevens reaction is a chemical reaction whereby treatment of tosylhydrazones with strong base gives alkenes. ... The Shapiro reaction or tosylhydrazone decomposition is an organic reaction in which a ketone or aldehyde is converted to an alkene through an intermediate hydrazone in the presence of 2 equivalents of strong base. ...

Olefin metathesis

Main article: Olefin metathesis

Alkenes can be prepared by exchange with other alkenes, in a reaction known as olefin metathesis. Frequently loss of ethene gas is used to drive the reaction towards a desired product. In many cases, a mixture of geometric isomers is obtained, but the reaction tolerates many functional groups. The method is particularly effective for the preparation of cyclic alkenes, as in this synthesis of muscone: Olefin metathesis or transalkylidenation (in some literature, a disproportionation) is an organic reaction which involves redistribution of olefinic (alkene) bonds. ... Olefin metathesis or transalkylidenation (in some literature, a disproportionation) is an organic reaction which involves redistribution of olefinic (alkene) bonds. ... Muscone is an organic compound that is the primary contributor to the odor of musk. ...

Use of palladium-catalyzed coupling reactions

Coupling reactions, most notably those catalyzed by palladium compounds, have become popular for the synthesis of alkenes.^[8] The Heck reaction provides a method for coupling an aryl halide to an alkene, for example in the synthesis of the pharmaceutical naproxen: 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. ... For other uses, see Palladium (disambiguation). ... In organic chemistry, the Heck reaction or the Mizoroki-Heck reaction couples an unsaturated halide or triflate with an alkene in a basic solution. ... Naproxen (INN) (IPA: ) is a non-steroidal anti-inflammatory drug (NSAID) commonly used for the reduction of mild to moderate pain, fever, inflammation and stiffness caused by conditions such as osteoarthritis, rheumatoid arthritis, psoriatic arthritis, gout, ankylosing spondylitis, injury (like fractures), menstrual cramps, tendonitis, bursitis, and the treatment of primary...

Other couplings, such as the Stille, Suzuki and Negishi involve the reaction of an alkenyl, allyl or aryl halide (or triflate) with an alkenyl, alkyl (not for Stille) or aryl derivative of a metal or metalloid. For example, Suzuki coupling has been used on a citronellal derivative for the synthesis of capparatriene, a natural product which is highly active against leukemia:^[9] A Stille cross coupling is a cross coupling reaction of an aryl halide with an aryl or alkenyl tin compound using a zero-valent palladium complex such as tetrakis(triphenylphosphine)palladium(0) as a catalyst. ... The Suzuki reaction is the chemical reaction of an aryl- or vinyl-boronic acid with an aryl- or vinyl-halide catalyzed by a palladium(0) complex. ... The Negishi coupling is a cross coupling reaction in organic chemistry involving an organozinc compound, an organic halide and a nickel or palladium catalyst creating a new carbon-carbon covalent bond [1] [2]: The halide X can be chloride, bromine or iodine but also a triflate or acetyloxy group with... Triflate, more formally known as trifluoromethanesulfonate, is a functional group with the formula CF3SO3-. The triflate group is often represented by -OTf, as opposed to -Tf. ... Metalloid is a term used in chemistry when classifying the chemical elements. ...

From alkynes

Reduction of alkynes is a useful method for the stereoselective synthesis of disubstituted alkenes. If the cis-alkene is desired, hydrogenation in the presence of Lindlar's catalyst is commonly used, though hydroboration followed by hydrolysis provides an alternative approach. Reduction of the alkyne by sodium metal in liquid ammonia gives the trans-alkene.^[10] 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. ... In chemistry, a stereoselectivity is the property of a chemical reaction that yields an unequal mixture of stereoisomers from a single reactant. ... Hydrogenation is a class of chemical reactions which result an addition of hydrogen (H2) usually to unsaturated organic compounds. ... A Lindlar catalyst is a palladium heterogeneous catalyst on calcium carbonate poisoned, deactivated, or conditioned by lead acetate, CaCO3, or lead. ... For sodium in the diet, see Salt. ... For other uses, see Ammonia (disambiguation). ...

For the preparation multisubstituted alkenes, carbometalation of alkynes can give rise to a large variety of alkene derivatives. Carbometalation is an organometallic reaction involving the nucleophilic addition to alkenes and alkynes of a diverse range of organometallic reagents such as organolithium compounds, organocopper compounds and Grignard reagents according to the following general alkyne scheme: The addition can yield the cis or trans isomer and with unsymmetrical alkynes the...

Rearrangements and related reactions

Alkenes can be synthesized from other alkenes via rearrangement reactions. Besides olefin metathesis (described above), a large number of pericyclic reactions can be used such as the ene reaction and the Cope rearrangement. 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. ... Olefin metathesis or transalkylidenation (in some literature, a disproportionation) is an organic reaction which involves redistribution of olefinic (alkene) bonds. ... In organic chemistry, a pericyclic reaction is a type of organic reaction wherein the transition state of molecule has a cyclic geometry, and the reaction progresses in a concerted-reactions fashion. ... Ene reactions are Group transfer reactions between an alkyne or alkene, or similar double bonded species and an allyl-like species. ... It has been suggested that Cope reaction be merged into this article or section. ...

In the Diels-Alder reaction, a cyclohexene derivative is prepared from a diene and a reactive or electron-deficient alkene. 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. ... Cyclohexene is a colorless clear liquid cycloalkene with an intense aversive characteristic sharp smell reminiscent of an oil refinery. ...

Nomenclature

IUPAC Names

To form the root of the IUPAC names for alkenes, simply change the -an- infix of the parent to -en-. For example, CH₃-CH₃ is the alkane ethANe. The name of CH₂=CH₂ is therefore ethENe. IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... Chemical structure of methane, the simplest alkane Alkanes, also known as paraffins, are chemical compounds that consist only of the elements carbon (C) and hydrogen (H) (i. ...

In higher alkenes, where isomers exist that differ in location of the double bond, the following numbering system is used: In chemistry, isomers are molecules with the same chemical formula and often with the same kinds of bonds between atoms, but in which the atoms are arranged differently. ...

1. Number the longest carbon chain that contains the double bond in the direction that gives the carbon atoms of the double bond the lowest possible numbers.
2. Indicate the location of the double bond by the location of its first carbon
3. Name branched or substituted alkenes in a manner similar to alkanes.
4. Number the carbon atoms, locate and name substituent groups, locate the double bond, and name the main chain

Naming substituted hex-1-enes

Chemical structure of methane, the simplest alkane Alkanes, also known as paraffins, are chemical compounds that consist only of the elements carbon (C) and hydrogen (H) (i. ... Image File history File links Size of this preview: 800 × 192 pixelsFull resolution (2115 × 507 pixel, file size: 10 KB, MIME type: image/png) File historyClick on a date/time to view the file as it appeared at that time. ... Image File history File links Size of this preview: 800 × 192 pixelsFull resolution (2115 × 507 pixel, file size: 10 KB, MIME type: image/png) File historyClick on a date/time to view the file as it appeared at that time. ...

The Cis-Trans notation

Main article: Cis-trans isomerism

In the specific case of disubstituted alkenes where the two carbons have one substituent each, Cis-trans notation may be used. If both substituents are on the same side of the bond, it's defined as (cis-). If the substituents are on either side of the bond, it's defined as (trans-). Cis-2-butene Trans-2-butene In chemistry, geometric isomerism or cis-trans isomerism is a form of stereoisomerism and describes the orientation of functional groups at the ends of a bond around which no rotation is possible. ... Cis-2-butene Trans-2-butene In chemistry, geometric isomerism or cis-trans isomerism is a form of stereoisomerism and describes the orientation of functional groups at the ends of a bond around which no rotation is possible. ...

cis-but-2-ene

trans-but-2-ene

Image File history File links Cis-2-butene. ... Image File history File links Trans-2-butene. ...

The E,Z notation

Main article: E-Z notation

When an alkene has more than one substituent (especially necessary with 3 or 4 substituents), the double bond geometry is described using the labels E and Z. These labels come from the German words "entgegen" meaning "opposite" and "zusammen" meaning "together". Alkenes with the higher priority groups (as determined by CIP rules) on the same side of the double bond have these groups together and are designated Z. Alkenes with the higher priority groups on opposite sides are designated E. A mnemonic to remember this: Z notation has the higher priority groups on "ze zame zide". The more complex stereochemistry of highly substituted alkenes (especially 3 or 4 substituents) cannot be defined using the cis-trans notation. ... To meet Wikipedias quality standards, this article may require cleanup. ...

The difference between E and Z isomers

Image File history File links Size of this preview: 800 × 274 pixel Image in higher resolution (1683 × 576 pixel, file size: 27 KB, MIME type: image/png) I, the creator of this work, hereby release it into the public domain. ... Image File history File links Size of this preview: 800 × 274 pixel Image in higher resolution (1683 × 576 pixel, file size: 27 KB, MIME type: image/png) I, the creator of this work, hereby release it into the public domain. ...

Groups containing C=C double bonds

IUPAC recognizes two names for hydrocarbon groups containing carbon-carbon double bonds, the vinyl group and the allyl group. .^[2] Chemical structure of the vinyl functional group. ... An allyl group is an alkene hydrocarbon group with the formula H2C=CH-CH2-. It is made up of a vinyl group, CH2=CH-, attached to a methylene -CH2. ...

See also

Look up Alkene in
Wiktionary, the free dictionary.

• Alpha-olefin
• Arenes are also alkenes but have very different properties due to aromaticity

Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 151 languages. ... Alpha-olefins are a family of compounds with a chemical formula CxH2x, distinguished by having a double bond at the primary or alpha position. ... An aromatic hydrocarbon (abbreviated as AH) or arene [1] is a hydrocarbon, the molecular structure of which incorporates one or more planar sets of six carbon atoms that are connected by delocalised electrons numbering the same as if they consisted of alternating single and double covalent bonds. ... Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. ...

References