Question

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

Explanation:

Step1: Identify the carbonyl type

The given carbonyl is an aromatic - conjugated cyclohexanone. Conjugation lowers the stretching frequency of the carbon - carbon double bond.

Step2: Recall the frequency ranges

Aromatic - conjugated ketones typically have carbonyl stretching frequencies in the range of 1680 - 1640 $cm^{-1}$.

Answer:

1655