Chapter 18.1, Problem 3P

Interpretation Introduction

Interpretation: Remove a proton from the alpha carbon of $\text{N,N-dimethylethanamide}$ but not from the alpha carbon of either $\text{N-methylethanamide}$ or $\text{ethanamide}$ has to be explained.

Concept introduction: The electrons left behind when a proton is removed from the alpha carbon of an amide are not readily delocalized.  This is because the nitrogen of the $-\text{NR}$ group of an amide also has a lone-pair that can be delocalized on to the carbonyl oxygen.

Thus the lone pair on the alpha carbon and the lone pair on the nitrogen compete for the delocalization onto the same oxygen.