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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.
The rule is violated when neighboring functional groups polarize the multiple bond, or in certain additions of hydrogen bromide (addition in the presence of peroxides and the Wohl-Ziegler reaction) which occur by a free-radical mechanism. Alkenes also react with halogens (X 2) to form haloalkanes with two neighboring halogen atoms in a halogen ...
A hydrohalogenation reaction is the electrophilic addition of hydrogen halides like hydrogen chloride or hydrogen bromide to alkenes to yield the corresponding haloalkanes. [ 1 ] [ 2 ] [ 3 ] 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 ...
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. [2] The one-step mechanism is known as the E2 reaction, and the two-step mechanism is known as the E1 reaction. The numbers refer not to the number of steps in the mechanism, but rather to the ...
The addition of halogens to alkenes proceeds via intermediate halonium ions. In special cases, such intermediates have been isolated. [5] Bromination is more selective than chlorination because the reaction is less exothermic. Illustrative of the bromination of an alkene is the route to the anesthetic halothane from trichloroethylene: [6]
The chain mechanism is as follows, using the chlorination of methane as an example: Initiation Ultraviolet radiation splits a chlorine molecule to two chlorine atom radicals. Methane chlorination: initiation Chain propagation (two steps) A radical abstracts a hydrogen atom from methane, leaving a primary methyl radical.
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.
The reaction mechanism for an alkene bromination can be described as follows. In the first step of the reaction, a bromine molecule approaches the electron-rich alkene carbon–carbon double bond. The bromine atom closer to the bond takes on a partial positive charge as its electrons are repelled by the electrons of the double bond.