Chapter 17, Problem 50PP

Interpretation Introduction

Interpretation:

The given compounds should be ranked in order or increasing ${\text{λ}}_{\text{max}}$.

Concept introduction:

• The π-systems of conjugated dienes absorb UV or visible light (200nm – 800nm).
• The wavelength of maximum absorption of a compound is called ${\text{λ}}_{\text{max}}$.
• The value of ${\text{λ}}_{\text{max}}$ is highly depending on the extent of conjugation (number of conjugated double bonds).                                                                                                       Conjugated double bonds are the $\text{C}\text{=}\text{C}$ bonds, which are separated by one σ-bond.
• According to Woodward-Fieser rule, the estimate value of ${\text{λ}}_{\text{max}}$ for some conjugated compounds are given in below table,

COMPOUND	${\text{λ}}_{\text{max}}$-value
	217nm
	258nm
	290nm

To rank: the given compounds in order or increasing ${\text{λ}}_{\text{max}}$..