Electrophilic addition

An organic reaction in which an electrophile attacks a multiple bond, followed by addition of another group across the bond. It commonly converts alkenes and alkynes into more saturated products.

Electrophile: An electron-deficient atom, ion, or molecule that accepts an electron pair to form a bond. It initiates addition by accepting electron density from the multiple bond.
Hydrohalogenation: Addition of a hydrogen halide across a carbon–carbon multiple bond. It is the standard example of adding hydrogen and halogen across an alkene.
Alkene: A hydrocarbon containing at least one carbon–carbon double bond. Its electron-rich pi bond is the usual site of electrophilic attack.
Nucleophilic addition: An addition reaction in which a nucleophile attacks an electron-deficient multiple bond, commonly a carbonyl group. It reverses the usual polarity pattern: the multiple bond is attacked by a nucleophile.
Bromination of alkenes: Addition of molecular bromine across an alkene to produce a vicinal dibromide. Its anti stereochemistry supports a bridged bromonium-ion mechanism.
Carbocation: An organic ion in which a carbon atom bears a positive charge. Many electrophilic additions proceed through this positively charged intermediate.
Acid-catalyzed hydration: Addition of water to an alkene under acidic conditions to form an alcohol. Protonation activates the alkene before water adds to the intermediate.
Alkyne: A hydrocarbon containing at least one carbon–carbon triple bond. Its pi bonds can also undergo electrophilic addition, often in successive steps.
Radical addition: An addition reaction initiated by radicals rather than by electrophiles or nucleophiles. Radical pathways can reverse hydrogen-halide regiochemistry under peroxide conditions.
Bromohydrin formation: Formation of a bromine-and-hydroxyl-substituted product by reaction of an alkene with bromine in water. It illustrates regioselective opening of a bromonium ion by water.

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