An unknown organic compound is analyzed using infrared (IR) spectroscopy, revealing a very strong, broad absorption band centered around 3300 cm⁻¹ and another strong absorption at approximately 1710 cm⁻¹. Based on these characteristic IR signals, what functional group is most likely present in this compound?
Show answer and explanation
The answer
Correct answer: B. The compound most likely contains a carboxylic acid functional group, exhibiting both O-H and C=O stretches.
Tested concept: IR spectroscopy and functional groups
Explanation
The presence of a very strong, broad absorption band around 3300 cm⁻¹ is characteristic of an O-H stretch, specifically one that is hydrogen-bonded, as found in alcohols or carboxylic acids. The strong absorption at approximately 1710 cm⁻¹ is characteristic of a C=O (carbonyl) stretch. The combination of both a broad O-H stretch and a C=O stretch in these regions is the hallmark of a carboxylic acid functional group. In carboxylic acids, the O-H stretch is particularly broad due to extensive hydrogen bonding, and the C=O stretch is strong.
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