Which reaction in each of the following pairs takes place more rapidly?

1. It is a two step reaction.

2. In this carbocation is formed.

3. In this negative ion will attack from the side where there is less number of bulkier groups.

3. In this negative ion will attack from the side where there is less number of bulkier groups.

This nucleophile is less sterically hindered.

The electron withdrawing oxygen increases a electrophilicity of the carbon that the nucleophile attacks.

Steric strain is decreased when the alkyl halide dissociates to form the carbocation because the hybridization of the carbon changes from sp3 to sp2, allowing the bond angle between the bulky groups to increase from 109.5° to 120°. therefore the carbocation is more stable and therefore is formed more rapidly.

Because the reactants are neutral, the reaction will be faster in the more polar solvent.