Question

Question: Propose a mechanism for each of the following reactions:

a.)

b.)

Short answer

The given reactions are examples of cyclic compound synthesis formed from intramolecular rearrangement within molecule. The two mechanisms are shown below.

a.)

Addition of acid

b.)

Imine formation

Step-by-step solution

(a) Mechanism of reaction

Reactant gets protonated when reacted with HCl and the resultant product undergoes intramolecular rearrangement reaction gives a five membered ring.

In next step base abstract a proton and OH gets protonated.

Addition of acid

(b) Mechanism of reaction

Reactants undergo reaction with acid gives an imine product. Then intramolecular rearrangement on the imine product forms a 6 membered ring in between the two phenyl rings.

Addition of traces of acid