Question

Show what happens in step-2 of the example if the solvent acts as a nucleophile (forming a bond to carbon) rather than as a base (removing a proton).

Short answer

Methanol acts as nucleophile and attacks the carbocation which neutralizes the positive charge on carbocation. But, oxygen acquires positive charge, and positive charge on electronegative atom is unstable.

Attack of methanol as nucleophile

Step-by-step solution

Attack of methanol as a nucleophile on carbocation:

Methanol acts as nucleophile and attacks the carbocation which neutralizes the positive charge on carbocation. But, oxygen acquires positive charge, and positive charge on electronegative atom is unstable.

Attack of methanol as nucleophile

Proton abstraction by methanol and formation of product:

In the second step, to neutralize positive charge on oxygen, methanol acts as base and abstracts proton, which neutralizes the positive charge on oxygen and forms the required product.