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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]
This reaction is considered Markovnikov because the halogen substituent attaches to the more substituted carbon. Hydration: Can occur either in syn or anti addition fashion, depending on the solution it is in; 50% of each orientation. This reaction is considered Markovnikov because the hydroxyl group attaches to the more substituted carbon.
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]
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.
Zaitsev's Rule was reported in 1875, and appeared just as his nemesis, Markovnikov, (who had made a prediction which the rule contradicts) was taking the Chair at Moscow University. Zaytsev received several honors: he was elected as a Corresponding member of the Russian Academy of Science , an honorary member of Kiev University , and he served ...
Markovnikov's rule predicts that the hydrogen atom is added to the carbon of the alkene functional group which has the greater number of hydrogen atoms (fewer alkyl substituents). Zaitsev's rule predicts that the major reaction product is the alkene with the more highly substituted (more stable) double bond.
The 1,4 adduct places the larger Br atom at a less congested site and includes a more highly substituted alkene moiety, while the 1,2 adduct is the result of the attack by the nucleophile (Br −) at the carbon of the allylic cation bearing the greatest positive charge (the more highly substituted carbon is the most likely place for the ...