What prominent absorption band in an infrared (IR) spectrum confirms the presence of a carboxylic acid -O-H group?
Answer and explanation
Correct answer: D. A very broad, intense band spanning 2500 to 3300 cm^-1 centered around 3000 cm^-1
- Step 1: Carboxylic acid O-H stretching is broadened by hydrogen bonding, spanning 2500-3300 cm^-1. Step 2. It overlaps and obscures the C-H stretching vibrations around 2950 cm^-1. Answer: A very broad, intense band spanning 2500 to 3300 cm^-1 centered around 3000 cm^-1. Why not the others: 1715 cm^-1 is the carbonyl C=O stretch; 3600 cm^-1 is non-hydrogen-bonded alcohol O-H.
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