Answer to Question #138208 in Other for Sarita bartwal

Question

Why is iodide ion a good nucleophile but a weak base?

Answer 1

The relative lack of basicity of the iodide anion in water is precisely what makes it a good nucleophile. Its lack of affinity toward protons - i.e. the protons of water - physically frees it to attack electrophilic atoms (not limited to carbon). There is little hydrogen bonding between iodide ion and water.