Question

question 15
what is the stretching frequency (in cm⁻¹) of the following carbonyl?
1685
1745
1715
none of the above

Explanation:

Step1: Identify the carbonyl type

The given carbonyl is an $\alpha,\beta -$ unsaturated cyclic ketone.

Step2: Recall frequency range

For $\alpha,\beta -$ unsaturated cyclic ketones, the carbon - oxygen stretching frequency is around 1680 - 1690 $cm^{-1}$ due to resonance and conjugation effects.

Answer:

A. 1685