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ELECTROPHILIC ADDITION

Alkenes are susceptible to attack by

electrophiles (lone pair acceptors).

This is because the C=C double bond is very electron rich due to the electron cloud of the  bond.

In an addition reaction, the C=C double bond opens up and an atom or group of atoms joins onto each C of the C=C double bond.

During the mechanism, a carbocation is formed. Where more than one carbocation can be formed, the main product will be formed from the more stable carbocation. In general:

 tertiary >secondary >primary carbocationcarbocationcarbocation

most stableleast stable

Reagent

Conditions

What happens

Overall equation

Mechanism

electrophilic addition

:Br-

Example 1

Example 2

e.g. but-2-ene + Br2

Reagent

Conditions

What happens

Overall equation

Mechanism

electrophilic addition

:

Br-

Example 3

Example 4

Reagent

Conditions

What happens

Overall equation

Mechanism

electrophilic addition

Example 7

Example 8