Examine the IR spectrum provided for Compound C. The peaks below 1500 cannot be used to make any structural assignments because they are in the fingerprint region. There are a few important peaks in this IR spectrum. What is each peak most likely due to? Hint: the large peak that streches from 2500-3500 is actually two peaks: there is a sharp peak around 3000 that is mostly hidden.

The answer is carboxylic acid and aromatic carbon

Explanation:

The spectral data reveals peaks in 2500-3500 cm-1 and 3000 cm-1. We can give the following exegesis to the data:

2500-3500 (stretch) ⇒ is presence of O-H. not likely free alchololic group as that would have shown a higher absorption; hence this is most likely to be carboxylic acid

3000 (sharp) ⇒ Alkene/Alkyne, shows some degree of unsaturation as opposed to an amide N-H bond (which is usually medium absorption). It is most likely an aromatic carbon

Note: The fingerprint region between 1500 cm-1 to 400 cm-1 can identify the compound as it is unique to it.