Question

what is the stretching frequency (in cm⁻¹) of the following carbonyl?
1750
1685
1715

Explanation:

Step1: Identify the carbonyl type

The given compound is an ester (aryl - alkyl ester).

Step2: Recall ester carbonyl stretching frequency range

Ester carbonyls typically have stretching frequencies in the range of 1735 - 1750 \(cm^{-1}\) for aliphatic esters and around 1715 - 1730 \(cm^{-1}\) for aromatic esters. The given ester is an aromatic - alkyl ester. Aromatic conjugation lowers the carbonyl stretching frequency compared to aliphatic esters.

Answer:

1715