Question

what is the stretching frequency (in cm⁻¹) of the following carbonyl?
none of the above
1655
1775
1715
1745

Explanation:

Step1: Identify the carbonyl type

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

Step2: Recall the stretching - frequency range

For $\alpha,\beta -$ unsaturated cyclic ketones, the carbon - oxygen double - bond ($C = O$) stretching frequency is around 1650 - 1680 $cm^{-1}$.

Answer:

1655