IR Spectroscopy of Functional Groups in Dicarboxylic Acids

Steps:

• Identify functional groups in compound R: two -COOH groups.
• Recall IR ranges: -COOH shows C=O stretch at 1710 cm⁻¹ (1640-1740 cm⁻¹) and broad O-H stretch at 2500-3300 cm⁻¹ (includes 2500-3000 cm⁻¹).
• Check statement A: only one type of group (C=O) absorbs in 1640-1740 cm⁻¹, though two instances.
• Verify statement B: two -COOH groups each contribute O-H absorption in 2500-3000 cm⁻¹.

Why B is correct:

• Each -COOH has an O-H group with broad absorption in 2500-3000 cm⁻¹ due to hydrogen bonding, so two groups fit the range.

Why the others are wrong:

• A: Only C=O absorbs strongly in 1640-1740 cm⁻¹; O-H does not, so not two distinct groups.
• C: O-H in -COOH is broad, not sharp.

Final answer: B