Explain β - elimination.

β-elimination is a chemical reaction in organic chemistry where a molecule loses two substituents from adjacent carbon atoms, resulting in the formation of a double bond. The name "β" refers to the carbon atom adjacent to the one from which the leaving groups are removed.

The general mechanism of β-elimination involves four steps:

Proton abstraction: A base abstracts a proton (usually a hydrogen) from the carbon atom adjacent to the one bearing the leaving groups, forming a carbanion intermediate.

Leaving group departure: One of the substituents adjacent to the carbanion leaves as a neutral molecule, typically a halide ion (e.g., Cl-, Br-) or a proton (H+).

π-bond formation: The electrons in the carbanion intermediate form a π-bond with the adjacent carbon atom, resulting in the formation of a double bond.

Deprotonation: Another base abstracts a proton from the newly formed double bond, yielding the final product.

The overall result of β-elimination is the conversion of a saturated compound (containing only single bonds) into an unsaturated compound (containing at least one double bond). β-elimination reactions are commonly observed in the synthesis of alkenes and alkynes from compounds known as β-haloalkanes or β-halogenoalkanes, where a halogen atom is located on a carbon atom adjacent to the carbon atom bearing the leaving groups.