Alkenes, unsaturated compounds, contain double carbon-carbon double bonds and undergo addition reactions. The weaker pi bond can be converted into two stronger sigma bonds in addition reactions. Regioselective reactions are those that depend on the reagent.

Alkenes react more than alkanes, so they are subject to addition reactions. This involves breaking the weak pi bond and adding two new groups across carbon-carbon double bonds to create a saturated compound.

The addition reaction is a two-step process

1. The electrophile attacks the double bond, forming a carbocation intermediary.

2. In the second step, the anti-ion reacts with the carbocation intermediate to form a saturated product.

If the two atoms responsible for adding to the double bond differ, an addition reaction can be governed by one of the following rules:

1.Markovnikov’s Rule: The nucleophile and electrophile both add to the less hindered carbon-atom, while the nucleophile increases the hindered carbon-atom of the double bonds.

2.Anti-Markovnikov’s Rule: The nucleophile and electrophile both add to the carbon atom with the most hindered double bond carbon atoms.

Markovnikov adds a stable carbocation intermediate to anti-Markovnikov. Markovnikov adds a stable major product, while anti-Markovnikov adds a less stable minor product.