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Dehydrohalogenation to give an alkene In chemistry , dehydrohalogenation is an elimination reaction which removes a hydrogen halide from a substrate . The reaction is usually associated with the synthesis of alkenes , but it has wider applications.
Such reactions give alkenes in the case of vicinal alkyl dihalides: [2] R 2 C(X)C(X)R 2 + M → R 2 C=CR 2 + MX 2. Most desirable from the perspective of remediation are dehalogenations by hydrogenolysis, i.e. the replacement of a C−X bond by a C−H bond. Such reactions are amenable to catalysis: R−X + H 2 → R−H + HX
A mixture of cis-decalin and CXB can simultaneously match optical index and density of PMMA. [1] Due to the moderate dielectric constant of CXB (ε = 7.9 [ 2 ] ), PMMA acquires charges that can be screened by the addition of salt (e.g. tetrabutyl ammonium bromide ), leading to a very good approximation of colloidal hard sphere . [ 3 ]
In chemistry, the haloform reaction (also referred to as the Lieben haloform reaction) is a chemical reaction in which a haloform (CHX 3, where X is a halogen) is produced by the exhaustive halogenation of an acetyl group (R−C(=O)CH 3, where R can be either a hydrogen atom, an alkyl or an aryl group), in the presence of a base.
Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, drugs. [1] This kind of conversion is in fact so common that a comprehensive overview is challenging. This article mainly deals with halogenation using elemental halogens (F 2, Cl 2, Br 2, I 2). Halides are also commonly ...
The Heck reaction (also called the Mizoroki–Heck reaction) [1] is the chemical reaction of an unsaturated halide (or triflate) with an alkene in the presence of a base and a palladium catalyst to form a substituted alkene. It is named after Tsutomu Mizoroki and Richard F. Heck.
Recently, the preferred method has reversed the order of the steps. After the oxidation, which is normally done with a peroxy acid, halogenation is done under basic conditions by use of dibromodifluoromethane for the halogen transfer step. This method was used to synthesize 1,8-diphenyl-1,3,5,7-octatetraene. Scheme 2.
An example of modest stereoselectivity is the dehydrohalogenation of 2-iodobutane which yields 60% trans-2-butene and 20% cis-2-butene. [5] Since alkene geometric isomers are also classified as diastereomers, this reaction would also be called diastereoselective.