Chapter 20, Problem 20.5P

Interpretation Introduction

(a)

Interpretation:

The complete and detailed mechanism for the given reaction is to be drawn, and the overall product(s) of the reaction is to be predicted.

Concept introduction:

The ${\text{OH}}^{-}$ is the nucleophile and attacks the electron poor $\text{C}$ of the amide. After nucleophilic-addition and -elimination to produce an initial carboxylic acid, the carboxylic acid is deprotonated irreversibly. Acid workup adds the proton back. The direct formation of the carboxylic acid from the amide is energetically unfavorable due to the negative charge being so poorly stabilized on $\text{N}$ in the leaving group. Therefore, the reaction is reversible through the second step. However, the proton transfer in Step 3 is irreversible. It is the critical step that drives the reaction toward products. Without this step, no appreciable amount of product would form.

Interpretation Introduction

(b)

Interpretation:

The complete and detailed mechanism for the given reaction is to be drawn and the overall product(s) of the reaction is to be predicted.

Concept introduction:

The ${\text{OH}}^{-}$ is the nucleophile and attacks the electron poor $\text{C}$ of the amide. After nucleophilic-addition and -elimination to produce an initial carboxylic acid, the carboxylic acid is deprotonated irreversibly. Acid workup adds the proton back. The direct formation of the carboxylic acid from the amide is energetically unfavorable due to the negative charge being so poorly stabilized on $\text{N}$ in the leaving group. Therefore, the reaction is reversible through the second step. However, the proton transfer in Step 3 is irreversible. It is the critical step that drives the reaction toward products. Without this step, no appreciable amount of product would form.