Chapter 14.23, Problem 25P

Interpretation Introduction

Interpretation:

The comparision of HONO-LUMO energy difference for the $\text{π}\to \text{π*}$ transition of ethylene and cis, trans-$1,3$-cyclooctadiene with the respective ${\text{λ}}_{\text{max}}$ values is to be determined.

Concept Introduction:

The energy of transition is related to the wavelength ${\text{λ}}_{\text{max}}$ of the absorbed radiation by Planck’s equation

$\Delta E=\frac{hc}{{\lambda }_{\max }}$

Here, $h=6.626\times {10}^{-34}{\text{m}}^2\text{ kg}/\text{s}$ is the Planck constant, $c=3\times {10}^8\text{m}/\text{s}$ is the speed of the light, and ${\lambda }_{\text{max}}$ is the maximum wavelength (between HOMO and LUMO).

The highest occupied molecular orbital (HOMO) in an alkene is the $\text{π}$ bonding molecular orbital. The lowest unoccupied molecular orbital (LUMO) is $\text{π*}$ antibonding molecular orbital.