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The anti-Markovnikov rule can be illustrated using the addition of hydrogen bromide to isobutylene in the presence of benzoyl peroxide or hydrogen peroxide. The reaction of HBr with substituted alkenes was prototypical in the study of free-radical additions. Early chemists discovered that the reason for the variability in the ratio of ...
In 1869, a Russian chemist named Vladimir Markovnikov demonstrated that the addition of HBr to alkenes usually but not always resulted in a specific orientation. Markovnikov's rule, which stems from these observations, states that in the addition of HBr or another hydrogen halide to an alkene, the acidic proton will add to the less substituted carbon of the double bond. [3]
For terminal olefins (or acetylenes), the regioselectivity of the process can be described as Markovnikov (addition of X at the substituted end) or anti-Markovnikov (addition of X at the unsubstituted end). Catalysts are frequently employed to control the chemo-, regio-, and stereoselectivity of hydrofunctionalization reactions.
If an epoxide mechanism is followed, hydroxide groups are added in an anti fashion. Neither Markovnikov or anti-Markovnikov because the substituents are the same. Hydrobromination: Stereospecific: Can be syn or anti addition, depending on situation. When alkenes undergo hydrobromination, the alkyl bromides are formed Markovnikov.
[3]: 188, 751 The result is typically anti-Markovnikov addition, a phenomenon Morris Kharasch called the "peroxide effect". [4] Reaction is slower with alkynes than alkenes. [3]: 750 In the paradigmatic example, hydrogen bromide radicalyzes to monatomic bromine. These bromine atoms add to an alkene at the most accessible site, to give a ...
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 ...
One example of a monoalkylborane is thexylborane (ThxBH 2), produced by the hydroboration of tetramethylethylene: [14] B 2 H 6 + 2 Me 2 C=CMe 2 → [Me 2 CHCMe 2 BH 2] 2. A chiral example is monoisopinocampheylborane. Although often written as IpcBH 2, it is a dimer [IpcBH 2] 2. It is obtained by hydroboration of (−)‐α‐pinene with borane ...
Basic schematic of thiol-ene addition reaction. The reaction results in an anti-Markovnikov addition of a thiol compound to an alkene. Given the stereoselectivity, high rate and yields, this synthetically useful reaction may underpin future applications in material and biomedical sciences. [2] [4]