See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Solution: Intramolecular Friedel-Crafts Acylation **Reaction Analysis:** The starting material is a cyclohexane ring with two adjacent $CH_3CO$ (acetyl) groups attached via carbonyl carbons in an ortho/1,3-relationship on the ring. Under acidic conditions with heat ($OH^⊖$, $\Delta$), this undergoes **intramolecular Friedel-Crafts acylation**: **Step 1:** The two carbonyl groups activate the aromatic ring toward electrophilic attack. **Step 2:** In acidic conditions, one carbonyl becomes a strong electrophile ($CH_3CO^⊕$). **Step 3:** The electron-rich $\pi$-system of the cyclohexadiene ring attacks the acylinium ion intramolecularly, forming a new $C-C$ bond. **Step 4:** This creates a six-membered aromatic ring (benzene ring) while simultaneously removing one acetyl group. **Result:** A **cyclohexanone fused with a benzene ring bearing an acetyl substituent** — this is **1-acetylindanone** or more simply, a benzene-fused cyclopentanone system with an acetyl group. **Why (A) is correct:** Option (A) shows a six-membered aromatic ring fused to a five-membered ring system with an acetyl ketone — exactly the product of intramolecular Friedel-Crafts acylation. Options (B), (C), and (D) show improper ring sizes or unsaturation patterns that don't result from this mechanism.