Final answer:
An NMR peak corresponding to a carboxylic acid (-COOH) proton would have a higher chemical shift, often above 5 ppm, due to the deshielding effect of the carbonyl group and resonance stabilization.
Step-by-step explanation:
Protons in carboxylic acids (-COOH) tend to display a higher chemical shift in NMR spectroscopy due to the electron-withdrawing effects of the carbonyl group (C=O) and the resonance stabilization when the carboxylic acid loses its proton and forms a carboxylate ion (-COO−). Compared to protons in environments with less deshielding, such as alkanes, the acidic proton of a carboxylic acid experiences a higher chemical shift, often above 5 ppm.
The presence of a broad peak in the IR spectrum—indicative of O-H stretching in alcohols—is analogous to the broad signal observed for the O-H stretch in carboxylic acids. In a carboxylic acid, the O-H stretch typically appears at around 3400 cm−1, while the carbonyl group shows a distinct peak, often observed around 1709 cm−1 in the case of octanoic acid.