Chapter 16, Problem 16.14P

Interpretation Introduction

Interpretation:

The protons A–C are to be ranked in order of increasing chemical shift.

Concept introduction:

A proton’s absorption peak is shifted downfield (i.e., to higher chemical shift) by nearby electronegative atoms. This downfield shift occurs because electronegative atoms are inductively electron withdrawing, so they remove electron density from the nearby proton. The proton is said to be deshielded resulting in a higher signal frequency, and thus a larger chemical shift. The inductive effect and magnetic anisotropy shifts the proton signal downfield leading to a higher chemical shift. The effects that cause deshielding are essentially additive.