Question

Question. Rank the following compounds in order of increasing frequency of the C=O absorption in their IR spectra.

Short answer

Answer

Step-by-step solution

Step-by-Step SolutionStep 1: IR Absorption

The compounds with active dipole moment would absorb IR radiation depending on the strength of the bond and the difference in the rotational and vibrational states.

Order of absorption

The presence of a bulky group as a substituent of the C=O linkage would lower the absorption.

The presence of an electron releasing group (ERG) would also reduce the absorption to a shorter frequency.

Cyclization would increase the strength of the C-O-C bond, making the compound absorb at a higher frequency.

Therefore, the increasing order of IR absorption based on increasing wavenumber is as follows: