Compound 'B' is :

Step 1: Nitrosation ($$\text{NaNO}_2 / \text{HCl}$$)

The starting material is a substituted phenol (thymol derivative). When treated with nitrous acid ($$\text{NaNO}_2 + \text{HCl}4$ forming $$\text{HNO}_2$$) at a low temperature, it undergoes electrophilic aromatic substitution (nitrosation).

• The hydroxyl group ($$\text{-OH}$$) is a strongly activating, ortho/para-directing group.
• The ortho positions relative to the $$\text{-OH}$$ group are hindered or occupied.
• The carbon position directly para to the $$\text{-OH}$$ group (the top-left vertex of the ring) is completely vacant and sterically accessible.

the nitroso electrophile ($$\text{NO}^+$$) attacks at this para-position to form Compound A (a para-nitrosophenol derivative).

Step 2: Selective Reduction ($$\text{NH}_4\text{SH}$$)

Compound A is then treated with ammonium hydrosulfide ($$\text{NH}_4\text{SH}$$).

• $$\text{NH}_4\text{SH}$$ is a well-known mild and selective reducing agent.
• It reduces the nitroso group ($$\text{-NO}$$) directly to a primary amino group ($$\text{-NH}_2$$) without affecting the other alkyl or phenolic substituents on the ring.

Option A