Chapter 15, Problem 15.11P

Interpretation Introduction

Interpretation:

Which of the following compounds has longer ${\text{λ}}_{\text{max}}$: ${\text{H}}_{\text{2}}{\text{C = NH}}_{\text{2}}^{\text{+}}$ or ${\text{H}}_{\text{2}}{\text{C = OH}}^{\text{+}}$ is to be determined and explained.

Concept introduction:

The longest ${\text{λ}}_{\text{max}}$ for a species that has an available $\text{n}\to {\text{π}}^{\text{*}}$ transition (due to the presence of a lone pair) will be significantly longer than a comparable species that does not have such a transition available. The value of the longest wavelength ${\text{λ}}_{\text{max}}$ increases as the extent of conjugation increases.