Chapter 3, Problem 57IP

Interpretation Introduction

Interpretation:

Constitutional isomers needed to be drawn for the given molecular formula ${\text{C}}_{\text{4}}{\text{H}}_{\text{9}}{\text{NO}}_{\text{2}}$ and identify the least acidic isomer (higher $\text{pka}$).

Concept introduction:

Constitutional isomers:

• Constitutional isomers are isomers which have the same molecular formula and different bond connectivity between the atoms in the molecule.

Acidic strength of the molecule depends on the stability of the Conjugate anion.

• If the conjugate anion is more resonance stabilized, the acid considered as strong acid and has less $\text{pka}$ corresponding anion is weak base. And the least stable anion has higher $\text{pka}$ value.
• If more sterically hindered the group, basic nature is more for that molecule. That means bulkiness increases the basic strength of the molecule. 

To draw: the constitutional isomers for the molecular formula ${\text{C}}_{\text{4}}{\text{H}}_{\text{9}}{\text{NO}}_{\text{2}}$.