Question

Question: Which of the highlighted bonds absorbs at higher $\mathbf{\nu }$in an IR spectrum?

Short answer

Answer

Step-by-step solution

IR Spectra

The IR spectra are obtained by irradiating the sample with light from the IR region (5000 to 500 ${\mathbf{cm}}^{\mathbf{-}\mathbf{1}}$) of the electromagnetic spectrum. IR is the only one that allows for the direct identification of the functional group.

Structure determination

The IR region of the spectrum extends from 4000 to 625 ${\mathbf{cm}}^{\mathbf{-}\mathbf{1}}$.The IR region is split into three parts.

(C=O) carbonyl stretching frequency is approximately 1650${\mathrm{cm}}^{-1}$

(C=C) carbon-carbon double bond stretching frequency is approximately 1500-1600${\mathrm{cm}}^{-1}$

(C-H) stretching frequency is approximately 1340-1470${\mathrm{cm}}^{-1}$

a

This molecule has a higher frequency because the carbonyl group is present.

b

This molecule has a higher frequency because the (C=N) group is present in it.

c

A higher frequency is observed for this molecule. It has a (C=C) group.