Identify the likely reaction sequence

The final options are about the identity/properties of compound $\mathbf{S}$. Among the options:

• option A refers to a drug like selegiline / MAO inhibitors,
• option B refers to aspirin,
• option C refers to a narcotic drug like heroin/morphine,
• option D is a chemical name: ortho-acetylbenzoic acid.

In standard organic chemistry reaction schemes involving a phenyl alkyl ether $\mathbf{P}$ giving an aromatic compound $\mathbf{Q}$ and then a major product $\mathbf{S}$, a very common path is:

$\text{anisole or phenyl alkyl ether} \xrightarrow[\text{cleavage}]{HI} \text{phenol } (\mathbf{Q})$

Then phenol on further reaction can lead to salicylic acid and then acetylation gives aspirin.

Interpret the compounds

Since $\mathbf{P}$ is a phenyl alkyl ether, cleavage of aryl-alkyl ether occurs at the alkyl–oxygen bond, producing:

$\mathrm{ArOR} \xrightarrow{HI} \mathrm{ArOH} + \mathrm{RI}$

Thus, $\mathbf{Q}$ is most plausibly phenol, an aromatic compound.

Formation of $\mathbf{S}$ from phenol-derived pathway

A standard sequence is:

• phenol $\rightarrow$ sodium phenoxide
• Kolbe reaction $\rightarrow$ salicylic acid
• acetylation with acetic anhydride $\rightarrow$ acetylsalicylic acid (aspirin)

Therefore, $\mathbf{S}$ is most likely aspirin.

Check the statements about aspirin

Aspirin acts by inhibiting the enzyme cyclooxygenase, thereby reducing the synthesis of prostaglandins.

So statement B is correct:

$\text{Aspirin inhibits the synthesis of prostaglandins.}$

Reject other options

• A: MAO inhibition is not the action of aspirin.
• C: Aspirin is not a narcotic drug.
• D: Aspirin is 2-acetoxybenzoic acid, not ortho-acetylbenzoic acid.

Final answer

The correct statement about $\mathbf{S}$ is Option B.