Final answer:
The strong sharp signal at 1715 cm-1 in the FTIR spectrum of a sample suggests the presence of a carbonyl group, specifically from a carboxylic acid, based on characteristic absorption frequencies of various functional groups.
Step-by-step explanation:
A strong, sharp signal at 1715 cm-1 in an FTIR spectrum is indicative of the presence of a carbonyl group. Specifically, this absorption is characteristic of a carbonyl group in a carboxylic acid. As discussed in infrared spectroscopy, various functional groups absorb infrared light at different characteristic frequencies. One of the most distinct absorptions is that of the carbonyl group, typically found in the 1650-1750 cm-1 range. The precise absorption frequency within this range can help differentiate subtypes of carbonyl-containing compounds such as esters, ketones, aldehydes, and carboxylic acids.
The strong and sharp nature of the peak suggests a non-conjugated carbonyl group, such as that found in a carboxylic acid, as conjugated systems tend to show a shift to slightly lower frequencies. Additionally, the absence of corresponding alkyne absorption peaks between 2100-2250 cm-1 and alcohol O-H bond stretching near 3400 cm-1 further supports the interpretation that the compound is a carboxylic acid. The importance of identifying functional groups like these lies in their distinct chemical behaviors and the roles they play in the structure and reactivity of organic molecules.