IR Spectroscopy for Functional Group Identification

Steps:

• Examine statement A: 1640-1740 cm⁻¹ range indicates carbonyl (C=O) stretches; two groups imply multiple carbonyls like in dicarboxylic acids.
• Examine statement B: 2500-3000 cm⁻¹ range matches broad O-H stretch in carboxylic acids due to hydrogen bonding.
• Examine statement C: Sharp absorption at 2500-3000 cm⁻¹ suggests alkyne C-H, not typical O-H which is broad.
• Determine compound R as carboxylic acid based on matching B's characteristics.

Why B is correct:

• Carboxylic acids exhibit a broad, strong O-H stretch from 2500-3300 cm⁻¹ due to dimer hydrogen bonding (IR correlation table).

Why the others are wrong:

• A: Carboxylic acids have one C=O per -COOH group; no evidence for two.
• C: O-H in carboxylic acids is broad, not sharp.
• D: Insufficient information provided.

Final answer: B