Question

Which is the better nucleophile in a protic solvent, chloride ion or bromide ion? Try to explain this in terms of the nature of the chloride ion and the bromide ion.

Answer 1

In a protic solvent bromide ion is better nucleophile than cloride ion.

Because in protic solvent ions are surrounded by water molecules and is called hydration.

extent of hydration depende on charge density on ion.

Among chloride and bromide bromide ion is larger so it is less hydrated or is surrounded by smaller number of water molecules.

Lesser hydration of bromide ion facilitates easier movement of bromide ion in the solution and henge greater nucleophilicity.