Question

what is the stretching frequency (in cm^-1) of the following carbonyl?
1765
1715
1775 and 1810
1685

Explanation:

Step1: Identify the carbonyl type

The given compound is an ester. Esters typically have carbon - oxygen double - bond (carbonyl) stretching frequencies in the range of 1735 - 1750 $cm^{-1}$ for simple esters. However, the presence of conjugation or ring - strain can affect this value. In this case, there is no significant conjugation that would lower the frequency greatly.

Step2: Evaluate the options

1765 $cm^{-1}$ is in the typical range for an ester carbonyl stretching frequency considering the structure. 1715 $cm^{-1}$ is too low for a non - conjugated ester carbonyl. The range 1775 - 1810 $cm^{-1}$ is more characteristic of acid chlorides. 1685 $cm^{-1}$ is characteristic of a conjugated carbonyl (such as in an $\alpha,\beta$-unsaturated carbonyl or an amide).

Answer:

1765