Question

Propose a mechanism that accounts for the formation of the product.

Short answer

The proposed mechanism is shown below.

Step-by-step solution

Attack of proton

The proton attacks the hydroxide ion and forms water. When this water molecule is removed, electron delocalization occurs.

Attack of proton

Cyclization of molecule

The lone pair of electron in nitrogen atom is shifted to pentene and the double bond in the pentene is shifted and becomes a single bond.

Cyclization of molecule

Release of Bronsted Acid BH+

BH⁺ is released after cyclisation and electron delocalization. So nitrogen forms a positive charge on it and the final product is obtained.

Release of Bronsted Acid BH⁺