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Such reactions are said to be anti-Markovnikov, since the halogen adds to the less substituted carbon, the opposite of a Markovnikov reaction. 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 ...
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]
The reaction follows Markovnikov's rule (the hydroxy group will always be added to the more substituted carbon). The oxymercuration part of the reaction involves anti addition of OH group but the demercuration part of the reaction involves free radical mechanism and is not stereospecific, i.e. H and OH may be syn or anti to each other.
In general, the adding radical attacks the alkene at the most sterically accessible (typically, least substituted) carbon; the radical then stabilizes on the more substituted carbon. [3]: 188, 751 The result is typically anti-Markovnikov addition, a phenomenon Morris Kharasch called the "peroxide effect". [4]
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This process is called Ad E 2 mechanism ("addition, electrophilic, second-order"). Iodine (I 2), chlorine (Cl 2), sulfenyl ion (RS +), mercury cation (Hg 2+), and dichlorocarbene (:CCl 2) also react through similar pathways. The direct conversion of 1 to 3 will appear when the Br − is large excess in the reaction medium.
1 Getting to know Markovnikov's rule. 1 comment. 2 Anthropomorphic terms. ... 3 comments. 4 Claim that hydroboration-oxidation is anti-Markovnikov. 2 comments. 5 The ...
Hydrosilylation, also called catalytic hydrosilation, describes the addition of Si-H bonds across unsaturated bonds. [1] Ordinarily the reaction is conducted catalytically and usually the substrates are unsaturated organic compounds. Alkenes and alkynes give alkyl and vinyl silanes; aldehydes and ketones give silyl ethers. Hydrosilylation has ...