Chapter 2.11, Problem 18P

Interpretation Introduction

a)

Interpretation:

The electrostatic potential map of imidazole is given. The most acidic hydrogen atom and most basic hydrogen atom in it are to be identified.

Concept introduction:

Electrostatic potential maps are useful because they show at a glance the electron rich and electron poor atoms in the molecule. The electron rich regions are shown in red and the electron poor regions are shown in blue.

To identify:

The most acidic hydrogen atom and most basic nitrogen atom in imidazole by looking at its electrostatic potential map.

Interpretation Introduction

b)

Interpretation:

Structures for the resonance forms of the products that result when imidazole is protonated by an acid and deprotonated by a base are to be drawn.

Concept introduction:

Resonance forms differ only in the placement of their π and nonbonding valence electrons. Neither the position nor the hybridization of any atom changes from one resonance form to another. For writing different resonance forms in the structure given, first a three atom groupings with a multiple bond and a p orbital with pair of electrons is to be identified. Then the exchange of position of double bond and electrons in p orbital will give another resonance form. The shift is represented by a curved arrow.

To identify:

Draw structures for the resonance forms of the products that result when imidazole is protonated by an acid and deprotonated by a base.