Question

Explain the relative chemical shifts of the benzene ring protons in Figure 14.18.

Short answer

For proton a it is 7.52 ppm.

For proton b it is 7.64 ppm.

For proton c it is 8.21 ppm.

Step-by-step solution

Step-by-Step SolutionStep 1: Chemical shift  value

The chemical shift represents the position of signals with respect to some standard reference compound TMS. It also represents the processional frequency of different protons present in a molecule.

The chemical shift value for each proton in a benzene ring is near about 7.2 ppm.

Chemical shift value for protons of the benzene ring

If the electron-withdrawing group is attached then de-sheilding occurs and the chemical shift value increases. Hence, chemical shift value for c proton is relatively high which is 8.21 ppm, while for proton a and b it is 7.52 ppm and 7.64 ppm, respectively.

Protons in benzene ring