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Subject - Organic Chemistry
The rule formulated in 1869 by V.V. Markovnikov (also Markownikoff) predicts the products of an electrophilic addition of asymmetrical reagents (e.g. hydrogen halides, water and alcohols) to asymmetric alkenes. It states that the reaction favors the formation of the regioisomer in which the more electrophilic part of the reagent has been added to the carbon atom of the double with the most hydrogens. The logic behind the Markovnikov rule is the understanding that in a two-step electrophilic addition the electrophile adds to the double bond in such a way that the more stable carbenium ion is formed as intermediate.
An addition product in which the addition occured opposite to the one predicted by the Markovnikov rule is called an anti-Markovnikov product. Mostly, this occurs inradical additions and also during hydroborations.
See also: Markovnikov product
Recommended Learning Units
HX Addition to Alkynes10 min.
This learning unit starts with a short introduction to the family of alkynes. Then the addition of HX to alkynes in comparison with the HX addition to alkenes and the halogenation of alkynes are described.
The addition of halogens to alkenes, its mechanism, and its stereochemistry are described in detail.