Chapter 15.4, Problem 8P

Interpretation Introduction

Interpretation:

The relative energy levels of the five π molecular orbitals of the cyclopenta dienyl system are similar to those in benzene. There is a single lowest energy MO, above which the orbitals come in degenerate pairs. A similar MO diagram is to be drawn for cyclopentadiene cation, radical and anion. How these mplecular orbitals are filled in all the three species is to be shown.

Concept introduction:

The numberof molecular orbitals formed is equal to the number of orbitals overlapping. The available orbitals are filled by the electrons in the increasing order of their energies. Each moleclar orbital can accommodate two electrons with opposite spin. Electrons occupy the orbitals individually first before they get paired in the same orbital.

The cyclopentadienyl cation has four electrons to be filled in molecular orbitals.

The cyclopentadienyl radical has five electrons to be filled in molecular orbitals.

The cyclopentadienyl anion has six electrons to be filled in molecular orbitals.

To draw:

The relative energy levels of the five π molecular orbitals of the cyclopenta dienyl cation, radical and anion.

To show:

How the five π molecular orbitals are filled in cyclopentadienyl cation, radical and anion.