Chapter 15, Problem 15.31P

Interpretation Introduction

Interpretation:

The longest-wavelength absorption of $\text{buta-1, 2-diene}$ is to be compared with the longest-wavelength absorption of $\text{buta-1, 3-diene}$ and the significant difference is to be explained.

Concept introduction:

${\lambda }_{\max }$ depends heavily on the extent of conjugation. The molecule that contains only one sigma bond and does not absorb in the UV or visible regions, the ${\lambda }_{\max }$ is much too smaller. On the other hand, a molecule that contains at least one pi bond and has a greater ${\lambda }_{\max }$ than about nearly $\text{160 nm}$, the value of the longest-wavelength ${\lambda }_{\max }$ increases as the extent of conjugation increases.