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Free-radical substitution with bromine is commonly used to prepare organobromine compounds. Carbonyl-containing, benzylic, allylic substrates are especially prone to this reactions. For example, the commercially significant bromoacetic acid is generated directly from acetic acid and bromine in the presence of phosphorus tribromide catalyst:
Most 1-bromoalkanes are prepared by free-radical addition of hydrogen bromide to the 1-alkene, which is 1-pentene in the case of 1-bromopentane. These conditions lead to anti-Markovnikov addition, giving the 1-bromo derivative. [2] It is also formed by the reaction of 1-pentanol with hydrogen bromide.
The main limitation of the traditional Wittig reaction is that the reaction proceeds mainly via the erythro betaine intermediate, which leads to the Z-alkene. The erythro betaine can be converted to the threo betaine using phenyllithium at low temperature. [18] This modification affords the E-alkene. The Schlosser variant of the Wittig reaction
The Heck reaction is the palladium-catalyzed coupling of an aryl or alkenyl halide with an alkene to form a substituted alkene. [2] Intramolecular variants of the reaction may be used to generate cyclic products containing endo or exo double bonds. Ring sizes produced by the intramolecular Heck reaction range from four to twenty-seven atoms.
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.
An enal (or alkenal) is an organic compound containing both alkene and aldehyde functional groups. In an α,β-unsaturated enal, the alkene is conjugated to the carbonyl group of the aldehyde (formyl group). [3] The simplest enal is acrolein (CH 2 =CHCHO). Other examples include cis-3-hexenal (essence of mowed lawns) and cinnamaldehyde (essence ...
In dehydrohalogenation reactions, the halogen and an adjacent proton are removed from halocarbons, thus forming an alkene. For example, with bromoethane and sodium hydroxide (NaOH) in ethanol, the hydroxide ion HO − abstracts a hydrogen atom. A Bromide ion is then lost, resulting in ethene, H 2 O and NaBr. Thus, haloalkanes can be converted ...
The largest example of this takes place in the alkylation units of petrochemical plants, which convert low-molecular-weight alkenes into high octane gasoline components. Electron-rich species such as phenols are also commonly alkylated to produce a variety of products; examples include linear alkylbenzenes used in the production of surfactants ...