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43-506: BH3 could refer to The molecule borane , which has a chemical formula of BH 3 . The Bcl-2 homology domain 3 . BH3, the Chinese abbreviation for Honkai Impact 3rd (Chinese: 崩坏3 ; pinyin: Bēng Huài 3 ) BH abbreviation for third edition of Biblia Hebraica (Kittel) [REDACTED] Topics referred to by the same term This disambiguation page lists articles associated with

86-521: A carbocation . The net result of the reaction will be an alcohol . The reaction equation for hydration of ethylene is: Hydrohalogenation involves addition of H−X to unsaturated hydrocarbons. This reaction results in new C−H and C−X σ bonds. The formation of the intermediate carbocation is selective and follows Markovnikov's rule . The hydrohalogenation of alkene will result in haloalkane . The reaction equation of HBr addition to ethylene is: Alkenes add to dienes to give cyclohexenes . This conversion

129-436: A homologous series of hydrocarbons with the general formula C n H 2 n with n being a >1 natural number (which is two hydrogens less than the corresponding alkane ). When n is four or more, isomers are possible, distinguished by the position and conformation of the double bond. Alkenes are generally colorless non-polar compounds, somewhat similar to alkanes but more reactive. The first few members of

172-474: A δ H of 4.5–6.5  ppm . The double bond will also deshield the hydrogen attached to the carbons adjacent to sp carbons, and this generates δ H =1.6–2. ppm peaks. Cis/trans isomers are distinguishable due to different J-coupling effect. Cis vicinal hydrogens will have coupling constants in the range of 6–14  Hz , whereas the trans will have coupling constants of 11–18 Hz. In their C NMR spectra of alkenes, double bonds also deshield

215-523: A C=C π bond in unsaturated hydrocarbons weakens the dissociation energy of the allylic C−H bonds. Thus, these groupings are susceptible to free radical substitution at these C-H sites as well as addition reactions at the C=C site. In the presence of radical initiators , allylic C-H bonds can be halogenated. The presence of two C=C bonds flanking one methylene, i.e., doubly allylic, results in particularly weak HC-H bonds. The high reactivity of these situations

258-405: A carbon chain, or at least one functional group attached to each carbon is the same for both. E- and Z- configuration can be used instead in a more general case where all four functional groups attached to carbon atoms in a double bond are different. E- and Z- are abbreviations of German words zusammen (together) and entgegen (opposite). In E- and Z-isomerism, each functional group is assigned

301-460: A double bond cannot occur at the bridgehead of a bridged ring system unless the rings are large enough. Following Fawcett and defining S as the total number of non-bridgehead atoms in the rings, bicyclic systems require S  ≥ 7 for stability and tricyclic systems require S  ≥ 11. In organic chemistry ,the prefixes cis- and trans- are used to describe the positions of functional groups attached to carbon atoms joined by

344-434: A double bond. In Latin, cis and trans mean "on this side of" and "on the other side of" respectively. Therefore, if the functional groups are both on the same side of the carbon chain, the bond is said to have cis- configuration, otherwise (i.e. the functional groups are on the opposite side of the carbon chain), the bond is said to have trans- configuration. For there to be cis- and trans- configurations, there must be

387-840: A feedstock for the petrochemical industry because they can participate in a wide variety of reactions, prominently polymerization and alkylation. Except for ethylene, alkenes have two sites of reactivity: the carbon–carbon pi-bond and the presence of allylic CH centers. The former dominates but the allylic sites are important too. Hydrogenation involves the addition of H 2 resulting in an alkane. The equation of hydrogenation of ethylene to form ethane is: Hydrogenation reactions usually require catalysts to increase their reaction rate . The total number of hydrogens that can be added to an unsaturated hydrocarbon depends on its degree of unsaturation . Similar to hydrogen, halogens added to double bonds. Halonium ions are intermediates. These reactions do not require catalysts. Bromine test

430-591: A more reliable β-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 Zaitsev's rule ). Two common methods of elimination reactions are dehydrohalogenation of alkyl halides and dehydration of alcohols. A typical example

473-488: A priority based on the Cahn–Ingold–Prelog priority rules . If the two groups with higher priority are on the same side of the double bond, the bond is assigned Z- configuration, otherwise (i.e. the two groups with higher priority are on the opposite side of the double bond), the bond is assigned E- configuration. Cis- and trans- configurations do not have a fixed relationship with E - and Z -configurations. Many of

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516-530: A reaction intermediate in the pyrolysis of diborane to produce higher boranes : Further steps give rise to successively higher boranes, with B 10 H 14 as the most stable end product contaminated with polymeric materials, and a little B 20 H 26 . Borane ammoniate, which is produced by a displacement reaction of other borane adducts, eliminates elemental hydrogen on heating to give borazine (HBNH) 3 . Borane adducts are widely used in organic synthesis for hydroboration , where BH 3 adds across

559-495: A reaction of ethylene with the organometallic compound triethylaluminium in the presence of nickel , cobalt , or platinum . One of the principal methods for alkene synthesis in the laboratory is the elimination reaction of alkyl halides, alcohols, and similar compounds. Most common is the β-elimination via the E2 or E1 mechanism. A commercially significant example is the production of vinyl chloride . The E2 mechanism provides

602-460: A stabilising agent is added to prevent the THF from oxidising the borane. A stability sequence for several common adducts of borane, estimated from spectroscopic and thermochemical data, is as follows: BH 3 has some soft acid characteristics as sulfur donors form more stable complexes than do oxygen donors. Aqueous solutions of BH 3 are extremely unstable. Molecular BH 3 is believed to be

645-413: A strong adduct with triethylamine ; using this adduct requires harsher conditions in hydroboration. This can be advantageous for cases such as hydroborating trienes to avoid polymerization. More sterically hindered tertiary and silyl amines can deliver borane to alkenes at room temperature. Borane(5) is the dihydrogen complex of borane. Its molecular formula is BH 5 or possibly BH 3 (η -H 2 ). It

688-467: A typical C-C single bond. Each carbon atom of the double bond uses its three sp hybrid orbitals to form sigma bonds to three atoms (the other carbon atom and two hydrogen atoms). The unhybridized 2p atomic orbitals, which lie perpendicular to the plane created by the axes of the three sp 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 of

731-561: Is an example of a Diels-Alder reaction . Such reaction proceed with retention of stereochemistry. The rates are sensitive to electron-withdrawing or electron-donating substituents. When irradiated by UV-light, alkenes dimerize to give cyclobutanes . Another example is the Schenck ene reaction , in which singlet oxygen reacts with an allylic structure to give a transposed allyl peroxide : Alkenes react with percarboxylic acids and even hydrogen peroxide to yield epoxides : For ethylene,

774-424: Is catalytic dehydrogenation , where an alkane loses hydrogen at high temperatures to produce a corresponding alkene. This is the reverse of the catalytic hydrogenation of alkenes. This process is also known as reforming . Both processes are endothermic and are driven towards the alkene at high temperatures by entropy . Catalytic synthesis of higher α-alkenes (of the type RCH=CH 2 ) can also be achieved by

817-406: Is different from Wikidata All article disambiguation pages All disambiguation pages Borane BH 3 is a trigonal planar molecule with D 3h symmetry. The experimentally determined B–H bond length is 119  pm . In the absence of other chemical species, it reacts with itself to form diborane . Thus, it is an intermediate in the preparation of diborane according to

860-456: Is itself called allene —and those with three or more overlapping bonds ( C=C=C=C , C=C=C=C=C , etc.) are called cumulenes . Alkenes having four or more carbon atoms can form diverse structural isomers . Most alkenes are also isomers of cycloalkanes . Acyclic alkene structural isomers with only one double bond follow: Many of these molecules exhibit cis – trans isomerism . There may also be chiral carbon atoms particularly within

903-438: Is more stable than borane–tetrahydrofuran may also be used. Hydroboration can be coupled with oxidation to give the hydroboration-oxidation reaction . In this reaction, the boryl group in the generated organoborane is substituted with a hydroxyl group . Phosphine-boranes , with the formula R 3−n H n PBH 3 , are adducts of organophosphines and borane. Borane adducts with amines are more widely used. Borane makes

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946-533: Is only stable at very low temperatures and its existence is confirmed in very low temperature. Borane(5) and methanium (CH 5 ) are isoelectronic . Its conjugate base is the borohydride anion. Alkene In organic chemistry , an alkene , or olefin , is a hydrocarbon containing a carbon –carbon double bond . The double bond may be internal or in the terminal position. Terminal alkenes are also known as α-olefins . The International Union of Pure and Applied Chemistry (IUPAC) recommends using

989-637: Is the [4+2]- cycloaddition of singlet oxygen with a diene such as cyclopentadiene to yield an endoperoxide : Terminal alkenes are precursors to polymers via processes termed polymerization . Some polymerizations are of great economic significance, as they generate the plastics polyethylene and polypropylene . Polymers from alkene are usually referred to as polyolefins although they contain no olefins. Polymerization can proceed via diverse mechanisms. Conjugated dienes such as buta-1,3-diene and isoprene (2-methylbuta-1,3-diene) also produce polymers, one example being natural rubber. The presence of

1032-402: Is the basis for certain free radical reactions, manifested in the chemistry of drying oils . Alkenes undergo olefin metathesis , which cleaves and interchanges the substituents of the alkene. A related reaction is ethenolysis : In transition metal alkene complexes , alkenes serve as ligands for metals. In this case, the π electron density is donated to the metal d orbitals. The stronger

1075-595: Is used to test the saturation of hydrocarbons. The bromine test can also be used as an indication of the degree of unsaturation for unsaturated hydrocarbons. Bromine number is defined as gram of bromine able to react with 100g of product. Similar as hydrogenation, the halogenation of bromine is also depend on the number of π bond. A higher bromine number indicates higher degree of unsaturation. The π bonds of alkenes hydrocarbons are also susceptible to hydration . The reaction usually involves strong acid as catalyst . The first step in hydration often involves formation of

1118-412: The E – Z notation for molecules with three or four different substituents (side groups). For example, of the isomers of butene , the two methyl groups of ( Z )-but-2 -ene (a.k.a. cis -2-butene) appear on the same side of the double bond, and in ( E )-but-2-ene (a.k.a. trans -2-butene) the methyl groups appear on opposite sides. These two isomers of butene have distinct properties. As predicted by

1161-532: The VSEPR model of electron pair repulsion, the molecular geometry of alkenes includes bond angles about each carbon atom in a double bond of about 120°. The angle may vary because of steric strain introduced by nonbonded interactions between functional groups attached to the carbon atoms of the double bond. For example, the C–C–C bond angle in propylene is 123.9°. For bridged alkenes, Bredt's rule states that

1204-493: The epoxidation is conducted on a very large scale industrially using oxygen in the presence of silver-based catalysts: Alkenes react with ozone, leading to the scission of the double bond. The process is called ozonolysis . Often the reaction procedure includes a mild reductant, such as dimethylsulfide ( SMe 2 ): When treated with a hot concentrated, acidified solution of KMnO 4 , alkenes are cleaved to form ketones and/or carboxylic acids . The stoichiometry of

1247-405: The C=C bond in alkenes to give trialkylboranes: This reaction is regioselective . Other borane derivatives can be used to give even higher regioselectivity. The product trialkylboranes can be converted to useful organic derivatives. With bulky alkenes one can prepare species such as [HBR 2 ] 2 , which are also useful reagents in more specialised applications. Borane dimethylsulfide which

1290-526: The US and Mideast and naphtha in Europe and Asia. Alkanes are broken apart at high temperatures, often in the presence of a zeolite catalyst, to produce a mixture of primarily aliphatic alkenes and lower molecular weight alkanes. The mixture is feedstock and temperature dependent, and separated by fractional distillation. This is mainly used for the manufacture of small alkenes (up to six carbons). Related to this

1333-466: The boiling and melting points of various alkenes with the corresponding alkane and alkyne analogues. In the IR spectrum, the stretching/compression of C=C bond gives a peak at 1670–1600  cm . The band is weak in symmetrical alkenes. The bending of C=C bond absorbs between 1000 and 650 cm wavelength In H NMR spectroscopy, the hydrogen bonded to the carbon adjacent to double bonds will give

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1376-616: The carbons, making them have low field shift. C=C double bonds usually have chemical shift of about 100–170 ppm. Like most other hydrocarbons , alkenes combust to give carbon dioxide and water. The combustion of alkenes release less energy than burning same molarity of saturated ones with same number of carbons. This trend can be clearly seen in the list of standard enthalpy of combustion of hydrocarbons. Alkenes are relatively stable compounds, but are more reactive than alkanes . Most reactions of alkenes involve additions to this pi bond, forming new single bonds . Alkenes serve as

1419-559: The donation is, the stronger the back bonding from the metal d orbital to π* anti-bonding orbital of the alkene. This effect lowers the bond order of the alkene and increases the C-C bond length . One example is the complex PtCl 3 (C 2 H 4 )] . These complexes are related to the mechanisms of metal-catalyzed reactions of unsaturated hydrocarbons. Alkenes are produced by hydrocarbon cracking . Raw materials are mostly natural-gas condensate components (principally ethane and propane) in

1462-447: The larger molecules (from C 5 ). The number of potential isomers increases rapidly with additional carbon atoms. A carbon–carbon double bond consists of a sigma bond and a 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), but not twice as strong. Double bonds are shorter than single bonds with an average bond length of 1.33 Å (133 pm ) vs 1.53 Å for

1505-469: The molecule and a half on the other. With a strength of 65 kcal/mol, the pi bond is significantly weaker than the sigma bond. Rotation about the carbon–carbon double bond is restricted because it incurs an energetic cost to break the alignment of the p orbitals on the two carbon atoms. Consequently cis or trans isomers interconvert so slowly that they can be freely handled at ambient conditions without isomerization. More complex alkenes may be named with

1548-438: The name "alkene" only for acyclic hydrocarbons with just one double bond; alkadiene , alkatriene , etc., or polyene for acyclic hydrocarbons with two or more double bonds; cycloalkene , cycloalkadiene , etc. for cyclic ones; and "olefin" for the general class – cyclic or acyclic, with one or more double bonds. Acyclic alkenes, with only one double bond and no other functional groups (also known as mono-enes ) form

1591-431: The photosensitiser, such as hydroxyl radicals , singlet oxygen or superoxide ion. Reactions of the excited sensitizer can involve electron or hydrogen transfer, usually with a reducing substrate (Type I reaction) or interaction with oxygen (Type II reaction). These various alternative processes and reactions can be controlled by choice of specific reaction conditions, leading to a wide range of products. A common example

1634-429: The physical properties of alkenes and alkanes are similar: they are colorless, nonpolar, and combustible. The physical state depends on molecular mass : like the corresponding saturated hydrocarbons, the simplest alkenes ( ethylene , propylene , and butene ) are gases at room temperature. Linear alkenes of approximately five to sixteen carbon atoms are liquids, and higher alkenes are waxy solids. The melting point of

1677-499: The reaction is sensitive to conditions. This reaction and the ozonolysis can be used to determine the position of a double bond in an unknown alkene. The oxidation can be stopped at the vicinal diol rather than full cleavage of the alkene by using osmium tetroxide or other oxidants: This reaction is called dihydroxylation . In the presence of an appropriate photosensitiser , such as methylene blue and light, alkenes can undergo reaction with reactive oxygen species generated by

1720-600: The reaction: The standard enthalpy of dimerization of BH 3 is estimated to be −170 kJ mol . The boron atom in BH 3 has 6 valence electrons . Consequently, it is a strong Lewis acid and reacts with any Lewis base ('L' in equation below) to form an adduct: in which the base donates its lone pair, forming a dative covalent bond . Such compounds are thermodynamically stable, but may be easily oxidised in air. Solutions containing borane dimethylsulfide and borane–tetrahydrofuran are commercially available; in tetrahydrofuran

1763-519: The same title formed as a letter–number combination. If an internal link led you here, you may wish to change the link to point directly to the intended article. Gaia BH3 , a binary system consisting of a K2 star and a probable black hole. Retrieved from " https://en.wikipedia.org/w/index.php?title=BH3&oldid=1219336389 " Category : Letter–number combination disambiguation pages Hidden categories: Articles containing simplified Chinese-language text Short description

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1806-551: The series are gases or liquids at room temperature. The simplest alkene, ethylene ( C 2 H 4 ) (or "ethene" in the IUPAC nomenclature ) is the organic compound produced on the largest scale industrially. Aromatic compounds are often drawn as cyclic alkenes, however their structure and properties are sufficiently distinct that they are not classified as alkenes or olefins. Hydrocarbons with two overlapping double bonds ( C=C=C ) are called allenes —the simplest such compound

1849-405: The solids also increases with increase in molecular mass. Alkenes generally have stronger smells than their corresponding alkanes. Ethylene has a sweet and musty odor. Strained alkenes, in particular, like norbornene and trans -cyclooctene are known to have strong, unpleasant odors, a fact consistent with the stronger π complexes they form with metal ions including copper. Below is a list of

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