IR spectrum identifies alcohol via O-H stretch

Steps:

• Scan spectrum for functional group bands: broad peak at 3200-3600 cm⁻¹ indicates O-H from hydrogen bonding.
• Check for carbonyl absorption: no peak at 1700-1750 cm⁻¹ rules out esters and aldehydes.
• Examine C-O stretch region: absorption at 1100-1200 cm⁻¹ consistent with secondary alcohol.
• Match fingerprint region: pattern aligns with propan-2-ol's branched structure.

Why D is correct:

• Propan-2-ol features a broad, intense O-H stretch due to hydrogen-bonded secondary alcohol group.

Why the others are wrong:

• A: Methyl ethanoate shows strong C=O stretch at ~1735 cm⁻¹, absent here.
• B: Methanol lacks the specific C-H and C-O pattern of propan-2-ol's isopropyl group.
• C: Propanal exhibits C=O at ~1725 cm⁻¹ and aldehyde C-H at 2700-2800 cm⁻¹, not observed.

Final answer: D