Question

FTIR spectra of a sample shows a strong sharp signal at 1715 cm-1. What functional group does the sample possibly have?

1) Carbonyl
2) C=C
3) C-H

Answer 1

A strong sharp signal at 1715 cm⁻¹ in an FTIR spectrum is indicative of a carbonyl group, distinguishing it from carbon-carbon double bonds and carbon-hydrogen bonds.

Step-by-step explanation:

The prominent, sharp signal observed at 1715 cm⁻¹ in the FTIR spectrum strongly indicates the presence of a carbonyl group within the sample. This distinctive absorption corresponds to the stretching vibration of the C=O bond, a characteristic feature of carbonyl compounds such as ketones, aldehydes, carboxylic acids, and esters.

The specificity of this absorption range (1700-1750 cm⁻¹) for carbonyl functionalities distinguishes them from other functional groups. Notably, the signal's location at 1715 cm⁻¹ eliminates the possibility of it being attributed to a carbon-carbon double bond (C=C), whose absorption typically occurs around 1650 cm⁻¹. Moreover, it deviates from the C-H stretching frequencies observed in alkanes, which generally manifest between 2900-3000 cm⁻¹. Consequently, the FTIR data strongly supports the presence of a carbonyl compound in the analyzed sample.