Markovnikov's rule

Markovnikov's rule predicts that, in addition of a hydrogen-containing reagent to an unsymmetrical alkene, hydrogen attaches to the carbon already bearing more hydrogens, while the other group attaches to the more substituted carbon.

Electrophilic addition: A reaction in which an electrophile and a nucleophile add across a multiple bond. The rule predicts the orientation of this reaction class for many alkenes.
Alkene: A hydrocarbon containing at least one carbon–carbon double bond. Unsymmetrical alkenes provide the two nonequivalent positions whose reaction orientation the rule predicts.
Vladimir Markovnikov: A Russian chemist who formulated the alkene-addition rule bearing his name in 1869. His empirical generalization supplied the rule's name and original statement.
Anti-Markovnikov addition: An addition reaction in which the incoming nonhydrogen group bonds to the less substituted alkene carbon. It names the opposite orientation and is produced by several distinct reaction pathways.
Carbocation: An organic ion in which a carbon atom bears a positive charge. Its relative stability often determines which alkene carbon receives the electrophile first.
Hydrohalogenation: Addition of a hydrogen halide across a carbon–carbon double bond. Applying the rule identifies which carbon receives halogen in the usual ionic pathway.
Organic chemistry: The chemistry of carbon compounds, including their structures, properties, reactions, and synthesis. The rule emerged as chemists sought patterns in reactions of carbon compounds.
Kharasch effect: The peroxide-promoted radical addition of hydrogen bromide to an alkene with reversed regiochemistry. This named exception is the classic peroxide-dependent reversal of Markovnikov addition.
Hyperconjugation: A stabilizing interaction involving electron delocalization from a sigma bond into an adjacent empty or partially filled orbital. It helps explain why more substituted carbocations usually form preferentially.
Acid-catalyzed hydration: Addition of water across an alkene under acidic conditions to form an alcohol. The rule predicts the major alcohol's orientation in typical carbocation-mediated hydration.

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