Question

Ketone C=O signals usually appear at 1720 cm⁻¹. If a C=O is present in a molecule with ring strain, how does this value change in comparison?

a. Shifts to higher wavenumber
b. Shifts to lower wavenumber
c. Remains unchanged
d. Disappears

Answer 1

The presence of ring strain in a molecule causes the C=O signal to shift to a lower wavenumber.

Step-by-step explanation:

The presence of ring strain in a molecule will cause the C=O signal to shift to a lower wavenumber. This means that the absorption peak will appear at a lower frequency compared to the normal C=O signal at 1720 cm⁻¹. The shift occurs because the ring strain affects the bonding structure of the molecule, causing a change in the energy required for the C=O bond to vibrate.