Chapter 15, Problem 15.6P

Interpretation Introduction

Interpretation:

${\text{λ}}_{\text{max}}$ for the longest wavelength absorption of ${\text{deca-1, 3, 5, 7, 9-pentaene (C}}_{10}{\text{H}}_{12}\text{)}$ is to be estimated on the basis of the trend given in Table 15-1.

Concept introduction:

${\text{λ}}_{\text{max}}$ depends heavily on the extent of conjugation. Molecules that contain only one sigma bond do not absorb in the UV or visible regions; the ${\text{λ}}_{\text{max}}$ is much too small. On the other hand, a molecule that contains at least one $\text{π}$ bond shows a ${\text{λ}}_{\text{max}}$ greater than $\text{300}$ nm. The value of ${\text{λ}}_{\text{max}}$ for the longest wavelength peak in the spectrum increases as the extent of conjugation increases.