In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond. Organic chemistry is a discipline within Chemistry which involves the scientific study of the structure properties composition reactions, and preparation In Chemistry, saturation has five different meanings In Physical chemistry, saturation is the point at which a Solution of a substance A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 ^[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. In Organic chemistry, functional groups are specific groups of Atoms within Molecules that are responsible for the characteristic Chemical reactions In Chemistry, a homologous series is a series of Organic compounds with a similar General formula, possessing similar chemical properties due to the presence In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. ^[2]

The simplest alkene is ethylene (C₂H₄), which has the International Union of Pure and Applied Chemistry (IUPAC) name ethene. Structure This Hydrocarbon has four Hydrogen Atoms bound to a pair of Carbon atoms that are connected by a Double bond. The International Union of Pure and Applied Chemistry ( IUPAC) (aɪjuːpæk or ay-yoo-pec) is an international Non-governmental organization Alkenes are also called olefins (an archaic synonym, widely used in the petrochemical industry). Petrochemicals are chemical products made from raw materials of Petroleum or other Hydrocarbon origin Aromatic compounds are often drawn as cyclic alkenes, but their structure and properties are different and they are not considered to be alkenes. ^[2]

Contents 1 Structure 1.1 Bonding 1.2 Shape 2 Physical properties 3 Chemical properties 3.1 Addition reactions 3.2 Oxidation 3.3 Polymerization 4 Synthesis 4.1 Industrial methods 4.2 Elimination reactions 4.3 Synthesis from carbonyl compounds 4.4 Olefin metathesis 4.5 Use of palladium-catalyzed coupling reactions 4.6 From alkynes 4.7 Rearrangements and related reactions 5 Nomenclature 5.1 IUPAC Names 5.2 The Cis-Trans notation 5.3 The E,Z notation 5.4 Groups containing C=C double bonds 6 See also 7 References

Structure

Bonding

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. In Chemistry, sigma bonds ( σ bonds) are the strongest type of covalent Chemical bond. In Chemistry, sigma bonds ( σ bonds) are the strongest type of covalent Chemical bond. In Chemistry, pi bonds ( π bonds) are covalent Chemical bonds where two lobes of one involved electron orbital overlap two lobes This double bond is stronger than a single covalent bond (611 kJ/mol for C=C vs. The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity The mole (symbol mol) is a unit of Amount of substance: it is an SI base unit, and almost the only unit to be used to measure this 347 kJ/mol for C—C) ^[1] and also shorter with an average bond length of 1. In Molecular geometry, bond length or bond distance is the average distance between nuclei of two bonded Atoms in a Molecule. 33 Angstroms (133 pm). An ångström or angstrom (symbol Å) (ˈɔːŋstrəm Swedish: ˈɔ̀ŋstrœm is an internationally recognized non- SI unit of length equal A picometre ( American spelling: picometer, symbol pm) is a unit of Length in the Metric system, equal to one trillionth

Each carbon of the double bond uses its three sp² hybrid orbitals to form sigma bonds to three atoms. -->In Chemistry 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.

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. This article is about the chemical concept For "isomerism" of atomic nuclei see Nuclear isomer. Trans-2-butenesvg|right|thumb|Trans-2-butene]] In Chemistry, cis-trans isomerism or geometric isomerism or configuration isomerism is a form of 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. Isomers Among the molecules which have the Chemical formula 48 four Isomers are Alkenes. In Chemistry, a methyl group is a Hydrophobic Alkyl Functional group named after Methane (4

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. In Chemistry, pi bonds ( π bonds) are covalent Chemical bonds where two lobes of one involved electron orbital overlap two lobes The misalignment of the p orbitals is less than expected because pyramidalization takes place (See: pyramidal alkene). In Atomic physics and Quantum chemistry, electron configuration is the arrangement of Electrons in an Atom, Molecule, or other In Chemistry, trigonal planar is a Molecular geometry with one atom at the center and three atoms at the corners of a triangle all in one plane Pyramidal alkenes are Alkenes in which the two Carbon Atoms making up the Double bond are not Coplanar with their four Substituents 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°. Cyclooctene is a Cycloalkene with an eight-membered ring It can exist as either the ''cis'' - or trans - Isomer with the cis -isomer In Aerospace engineering, the Dihedral is the Angle between the two wings see Dihedral. This explains the dipole moment of 0. In physics there are two kinds of dipoles ( Hellènic: di(s- = two- and pòla = pivot hinge An electric dipole is a 8 D for this compound (cis-isomer 0. The debye (symbol D) is a non- SI, CGS unit of electrical dipole moment. Trans-2-butenesvg|right|thumb|Trans-2-butene]] In Chemistry, cis-trans isomerism or geometric isomerism or configuration isomerism is a form of 4 D) where a value of zero is expected. ^[3] The trans isomer of cycloheptene is only stable at low temperatures. Cycloheptene is a 7-membered Cycloalkene. It is a raw material in Organic chemistry and a Monomer in polymer synthesis

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°. Valence shell electron pair repulsion (VSEPR theory (1957 is a model in Chemistry, which is used for predicting the shapes of individual Molecules based The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Molecular geometry or molecular structure is the three- Dimensional arrangement of the Atoms that constitute a Molecule. Molecular geometry or molecular structure is the three- Dimensional arrangement of the Atoms that constitute a Molecule. The angle may vary because of steric strain introduced by nonbonded interactions created by functional groups attached to the carbons of the double bond. In Chemistry, van der Waals strain is strain resulting from van der Waals repulsion when two Substituents in a Molecule approach each In Physics, Chemistry, and Biology, intermolecular forces are forces that act between stable Molecules or between functional groups of In Organic chemistry, functional groups are specific groups of Atoms within Molecules that are responsible for the characteristic Chemical reactions For example, the C-C-C bond angle in propylene is 123. Propene, also known as propylene, is an unsaturated organic compound having the Chemical formula C 3 H 6 9°.

Physical properties

The physical properties of alkenes are comparable with alkanes. Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i The physical state depends on molecular mass (gases from ethene to butene - liquids from pentene onwards). A state of matter (or physical state, or form of matter) has physical properties which are qualitatively different from other states of matter The molecular mass (abbreviated m of a substance, more commonly referred to as molecular weight and abbreviated as MW, is the Mass of one The simplest alkenes, ethylene, propylene and butylene are gases. Structure This Hydrocarbon has four Hydrogen Atoms bound to a pair of Carbon atoms that are connected by a Double bond. Propene, also known as propylene, is an unsaturated organic compound having the Chemical formula C 3 H 6 Isomers Among the molecules which have the Chemical formula 48 four Isomers are Alkenes. Linear alkenes of approximately five to sixteen carbons are liquids, and higher alkenes are waxy solids.

Chemical properties

Alkenes are relatively stable compounds, but are more reactive than alkanes due to the presence of a carbon-carbon pi-bond. Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i The majority of the reactions of alkenes involve the rupture of this pi bond, forming new single bonds. In Chemistry, sigma bonds ( σ bonds) are the strongest 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 or other 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. Hydrogenation is the Chemical reaction that results in addition of Hydrogen (H2 Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i The reaction is carried out under pressure in the presence of a metallic catalyst. Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Common industrial catalysts are based on platinum, nickel or palladium. Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 Palladium (pronounced \pəˈleɪdiəm\ is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it palladium after the For laboratory syntheses, Raney nickel is often employed. Raney nickel (ˈreɪniː ˈnɪkəl is a solid Catalyst composed of fine grains of a Nickel - Aluminium Alloy, used in many industrial processes This is an alloy of nickel and aluminium. An alloy is a Solid solution or Homogeneous mixture of two or more elements, at least one of which is a Metal, which itself has Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 WikipediaNaming 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. Structure This Hydrocarbon has four Hydrogen Atoms bound to a pair of Carbon atoms that are connected by a Double bond. ETHANE is a mnemonic indicating a protocol used by Emergency services to report situations which they may be faced with especially as it relates to major incidents where In Organic chemistry, an electrophilic addition reaction is an Addition reaction where in a Chemical compound, a Pi bond is removed by the creation In Organic chemistry, an electrophilic addition reaction is an Addition reaction where in a Chemical compound, a Pi bond is removed by the creation An example is the Prins reaction where the electrophile is a carbonyl group. Prins reaction is an Organic reaction consisting of an Electrophilic addition of an Aldehyde or Ketone to an Alkene or Alkyne In Organic chemistry, a carbonyl group is a Functional group composed of a Carbon Atom double-bonded to an Oxygen
• Halogenation: Addition of elementary bromine or chlorine to alkenes yields vicinal dibromo- and dichloroalkanes, respectively. "Fluorination" redirects here For the addition of fluoride to drinking water see Water fluoridation. Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and In Chemistry vicinal (from Latin vicinus = neighbour stands for any two Functional groups bonded to two adjacent Carbon atoms 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. Bromine number is the amount of Bromine in grams absorbed by 100 grams of a sample 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. A hydrohalogenation reaction is the Electrophilic addition of Hydrohalic acids like Hydrogen chloride or Hydrogen bromide to Alkenes Hydrogen halides (or hydrohalic acids) are acids resulting from the chemical reaction of Hydrogen with one of the Halogen elements ( Fluorine, Hydrogen bromide is the diatomic molecule H[[Bromine Br]] Under standard conditions HBr is a gas but it can be liquified The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of Chemical compounds consisting of Alkanes such as Methane

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). In Chemistry, Markovnikov's rule or Markownikoff's rule is an Observation based on Zaitsev's rule.

This is the reaction mechanism for hydrohalogenation:

• Addition of a carbene or carbenoid yields the corresponding cyclopropane. In Chemistry, a carbene is a highly reactive Organic molecule containing a Carbon atom with six valence electrons and having the general formula In Chemistry a carbenoid is a Reactive intermediate that shares reaction characteristics with a Carbene. Cyclopropane is a Cycloalkane Molecule with the molecular formula C3H6 consisting of three Carbon Atoms linked to

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 In Organic An oxidizing agent or oxidising agent (also called an oxidant, oxidizer or oxidiser) can be defined as either a Chemical compound

• In the presence of oxygen, alkenes burn with a bright flame to produce carbon dioxide and water. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single
• 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. Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Carboxylic acids are Organic acids characterized by the presence of a Carboxyl group, which has the formula -C(=OOH usually written -COOH or -CO2H An epoxide is a cyclic Ether with only three ring atoms This ring approximately is an Equilateral triangle, i Ozonolysis is the cleavage of an Alkene or Alkyne with Ozone to form Organic compounds in which the multiple Carbon-carbon bond has An aldehyde is an organic compound containing a terminal Carbonyl 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

• Sharpless bishydroxylation and the Woodward cis-hydroxylation give diols

Polymerization

Polymerization of alkenes is an economically important reaction which yields polymers of high industrial value, such as the plastics polyethylene and polypropylene. Sharpless asymmetric dihydroxylation (also called the Sharpless bishydroxylation) is the Chemical reaction of an Alkene with Osmium tetroxide 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 or glycol is a Chemical compound containing two Hydroxyl groups (-OH groups Vicinal diols have hydroxyl groups attached to adjacent atoms In Polymer chemistry, polymerization is a process of reacting Monomer Molecules together in a Chemical reaction to form three-dimensional networks A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds Polyethylene or polythene ( IUPAC name poly(ethene) is a Thermoplastic commodity heavily used in consumer products (notably the Polypropylene or polypropene ( PP) is a Thermoplastic Polymer, made by the Chemical industry and used in a wide variety of applications Polymerization can either proceed via a free-radical or an ionic mechanism. In Chemistry, radicals (often referred to as free radicals) are atoms molecules or ions with Unpaired electrons on an otherwise Open shell

Synthesis

Industrial methods

The most common industrial synthesis of alkenes is based on cracking of petroleum. In Petroleum geology and Chemistry, cracking is the process whereby complex organic Molecules such as Kerogens or heavy Hydrocarbons Petroleum ( L petroleum, from Greek πετρέλαιον, lit 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. Zeolites (Greek zein, "to boil" lithos, "a stone" are hydrated Aluminosilicate Minerals and have a micro-porous structure This is mainly used for the manufacture of small alkenes (up to six carbons). ^[1]

Related to this is catalytic dehydrogenation, where an alkane loses hydrogen at high temperatures to produce a corresponding alkene. Dehydrogenation is a chemical reaction that involves the elimination of Hydrogen (H2 ^[1] This is the reverse of the catalytic hydrogenation of alkenes. Hydrogenation is the Chemical reaction that results in addition of Hydrogen (H2

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). In Thermodynamics (a branch of Physics) entropy, symbolized by S, is a measure of the unavailability of a system ’s Energy

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. Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Organometallic chemistry is the study of Chemical compounds containing bonds between Carbon and a Metal. Triethylaluminium or TEA is a volatile Organometallic compound which is used in various chemical processing and as an ignitor for jet and rocket Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 Cobalt (ˈkoʊbɒlt is a hard lustrous silver-grey Metal, a Chemical element with symbol Co. Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78

Elimination reactions

One of the principal methods for alkene synthesis in the laboratory is the elimination of alkyl halides, alcohols and similar compounds. 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. Most common is the -elimination via the E2 or E1 mechanism, ^[4] but -eliminations are also known.

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). A tosyl group (abbreviated Ts or Tos) combines the Toluene and Sulfonyl Functional groups. Triflate, more formally known as trifluoromethanesulfonate, is a Functional group with the formula CF3SO3- When an alkyl halide is used, the reaction is called a dehydrohalogenation. Dehydrohalogenation is an Organic chemistry reaction from which an Alkene is obtained from an Alkyl halide. For unsymmetrical products the more substituted alkenes (those with fewer hydrogens attached to the C=C) tend to predominate (see Saytzeff's rule). In Chemistry, Zaitsev's rule, Saytzeff's rule or Saytsev's rule named after Alexander Mikhailovich Zaitsev (number of different spellings due 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]

Alkenes can be synthesized from alcohols via dehydration, in which case water is lost via the E1 mechanism. In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon In Chemistry, a dehydration reaction is usually defined as a chemical reaction that involves the loss of water from the reacting molecule For example, the dehydration of ethanol produces ethene:

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

An alcohol may also be converted to a better leaving group (e. Sulfuric (or sulphuric acid, H 2 S[[oxygen O]]4 is a strong Mineral acid. Structure This Hydrocarbon has four Hydrogen Atoms bound to a pair of Carbon atoms that are connected by a Double bond. g. , xanthate), so as to allow a milder syn-elimination such as the Chugaev elimination and the Grieco elimination. Xanthates are the Salts and Esters of a xanthic acid ROC(=SSH or O-esters of dithiocarbonic acid where R is any organic residue The Chugaev elimination is a chemical reaction that involves the elimination of water from primary Alcohols to produce terminal Alkenes The intermediate is a Xanthate The Grieco elimination is an Organic reaction describing the Elimination reaction of an aliphatic primary Alcohol through a Selenide to a terminal Related reactions include eliminations by β-haloethers (the Boord olefin synthesis) and esters (ester pyrolysis). 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 Ester pyrolysis in Organic chemistry is a Vacuum pyrolysis reaction converting Esters containing a β-hydrogen atom into the corresponding Carboxylic

Alkenes can be prepared indirectly from alkyl amines. Amines are Organic compounds and Functional groups that contain a basic Nitrogen Atom with a Lone pair. 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. Alkylation is the transfer of an Alkyl group from one Molecule to another Hofmann elimination (also known as exhaustive methylation) is a process where an Amine is reacted to create a tertiary amine and an Alkene by treatment An amine oxide, also known as amine- N -oxide and N -oxide, is a Chemical compound that contains the Functional group R3N+-O&minus The Cope reaction or Cope elimination, developed by Arthur C Cope, is an Elimination reaction of an Amine oxide to form an Alkene Hofmann elimination is unusual in that the less substituted (non-Saytseff) alkene is usually the major product. In Chemistry, Zaitsev's rule, Saytzeff's rule or Saytsev's rule named after Alexander Mikhailovich Zaitsev (number of different spellings due The Cope reaction is a syn-elimination that occurs at or below 150 °C, for example:^[6]

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

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. An aldehyde is an organic compound containing a terminal Carbonyl 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 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 Such reactions are sometimes called olefinations. The most well-known of these methods is the Wittig reaction, but other related methods are known.

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 reaction is a Chemical reaction of an Aldehyde or Ketone with a triphenyl phosphonium ylide (often called a Wittig reagent Triphenylphosphine oxide is the Chemical compound with the formula OP(C6H53 The Wittig reagent is itself prepared easily from triphenylphosphine and an alkyl halide. Triphenylphosphine (in Europe triphenylphosphane is a common Organophosphorus compound with the formula P(C6H53 - often abbreviated to The reaction is quite general and many functional groups are tolerated, even esters, as in this example:^[7]

Related to the Wittig reaction is the Peterson olefination. The Peterson olefination (also called the Peterson reaction is the Chemical reaction of α-silyl carbanions 1 with Ketones (or Aldehydes to form 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 Julia olefination (also known as the Julia–Lythgoe olefination) is the Chemical reaction of Phenyl Sulfones ( 1) with Aldehydes In Organic chemistry, the phenyl group or phenyl ring (often abbreviated as -Ph) is the Functional group with the formula - A sulfone is a Chemical compound containing a Sulfonyl Functional group attached to two carbon atoms The Takai olefination based on an organochromium intermediate also delivers E-products. Takai olefination in Organic chemistry describes the Organic reaction of an Aldehyde with a diorganochromium compound to form an Alkene A titanium compound, Tebbe's reagent, is useful for the synthesis of methylene compounds; in this case, even esters and amides react. The Tebbe reagent is (C5H52TiCH2ClAl(CH32 an Organometallic compound used in the methylenation of Carbonyl

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). 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 If two different ketones are to be coupled, a more complex, indirect method such as the Barton-Kellogg reaction may be used. The Barton-Kellogg reaction is a Coupling reaction between a Ketone and a Thioketone through a Diazo intermediate forming an Alkene

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). Sodium methoxide is a chemical compound, with formula Na(CH3O The Bamford-Stevens reaction is a Chemical reaction whereby treatment of Tosylhydrazones with strong base gives Alkenes It is named for the British chemist The Shapiro reaction or tosylhydrazone decomposition is an Organic reaction in which a Ketone or Aldehyde is converted to an Alkene

Olefin metathesis

Main article: Olefin metathesis

Alkenes can be prepared by exchange with other alkenes, in a reaction known as olefin metathesis. Olefin metathesis or transalkylidenation is an Organic reaction that entails redistribution of alkylene fragments by the scission of carbon - carbon double bonds Olefin metathesis or transalkylidenation is an Organic reaction that entails redistribution of alkylene fragments by the scission of carbon - carbon double bonds 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:

Use of palladium-catalyzed coupling reactions

Coupling reactions, most notably those catalyzed by palladium compounds, have become popular for the synthesis of alkenes. Muscone is an Organic compound that is the primary contributor to the odor of Musk. A coupling reaction or oxidative coupling in Organic chemistry is a catch-all for a range of reactions in organometallic chemistry where two Hydrocarbon Palladium (pronounced \pəˈleɪdiəm\ is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it palladium after the ^[8] The Heck reaction provides a method for coupling an aryl halide to an alkene, for example in the synthesis of the pharmaceutical naproxen:

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. The Heck reaction (also called the Mizoroki-Heck reaction) is the Chemical reaction of an unsaturated Halide (or Triflate) with an Alkene Naproxen ( INN) (nəˈprɒksən is a Non-steroidal anti-inflammatory drug (NSAID commonly used for the reduction of moderate to severe Pain, Fever The Stille reaction is a Chemical reaction coupling an Organotin compound with an sp2-hybridized organic Halide catalyzed by Palladium The Suzuki reaction is the Organic reaction of an Aryl - or Vinyl - Boronic acid with an Aryl - or Vinyl - Halide The Negishi coupling is a Cross coupling reaction in Organic chemistry involving an Organozinc compound, an organic Halide and a Nickel Triflate, more formally known as trifluoromethanesulfonate, is a Functional group with the formula CF3SO3- Metalloid is a term used in Chemistry when classifying the Chemical elements On the basis of their general physical and chemical properties nearly every element 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]

From alkynes

Reduction of alkynes is a useful method for the stereoselective synthesis of disubstituted alkenes. Alkynes are Hydrocarbons that have at least one Triple bond between two Carbon atoms with the formula CnH2n-2. In Chemistry, stereoselectivity is the property of a Chemical reaction that yields an unequal mixture of stereoisomers from a single Reactant 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. Hydrogenation is the Chemical reaction that results in addition of Hydrogen (H2 A Lindlar catalyst is a Heterogeneous Catalyst that consists of Palladium deposited on Calcium carbonate and treated with various forms Reduction of the alkyne by sodium metal in liquid ammonia gives the trans-alkene. Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor ^[10]

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

Rearrangements and related reactions

Alkenes can be synthesized from other alkenes via rearrangement reactions. 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 Besides olefin metathesis (described above), a large number of pericyclic reactions can be used such as the ene reaction and the Cope rearrangement. Olefin metathesis or transalkylidenation is an Organic reaction that entails redistribution of alkylene fragments by the scission of carbon - carbon double bonds In Organic chemistry, a pericyclic reaction is a type of Organic reaction wherein the Transition state of the molecule has a cyclic geometry and the reaction The Ene reaction (also known as the Alder-ene reaction) is a Chemical reaction between an Alkene with an Allylic Hydrogen (the The Cope rearrangement is an extensively studied Organic reaction involving the [33]-sigmatropic rearrangement of 15-dienes.

In the Diels-Alder reaction, a cyclohexene derivative is prepared from a diene and a reactive or electron-deficient alkene. The Diels-Alder reaction is an Organic chemical reaction (specifically a Cycloaddition) between a conjugated Diene and a substituted Alkene, 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-. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general For example, CH₃-CH₃ is the alkane ethANe. Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i The name of CH₂=CH₂ is therefore ethENe.

In higher alkenes, where isomers exist that differ in location of the double bond, the following numbering system is used:

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. This article is about the chemical concept For "isomerism" of atomic nuclei see Nuclear isomer.
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. Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i
4. Number the carbon atoms, locate and name substituent groups, locate the double bond, and name the main chain

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. Trans-2-butenesvg|right|thumb|Trans-2-butene]] In Chemistry, cis-trans isomerism or geometric isomerism or configuration isomerism is a form of Trans-2-butenesvg|right|thumb|Trans-2-butene]] In Chemistry, cis-trans isomerism or geometric isomerism or configuration isomerism is a form of 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-).

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. The more complex Stereochemistry of highly substituted Alkenes (especially 3 or 4 substituents cannot be defined using the Cis-trans notation 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".

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. A vinyl compound is any Organic compound that contains a vinyl group (also called ethenyl) &minus C[[Hydrogen H]] =CH sub>2 An allyl group is an Alkene Hydrocarbon group with the formula H2C=CH-CH2- . ^[2]

See also

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

References

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