Chapter 15, Problem 15.46E

Interpretation Introduction

Interpretation:

The reason as to why $S_{11}=S_{22}=S_{33}=S_{44}$ in the Hückel approximation of the $\pi$ orbitals of butadiene is to be justified in words.

Concept introduction:

Hückel theory deals with the conjugated systems. In this theory, the $\pi$ and $\sigma$ bonds are treated separately. It states that the $\sigma$ bonds form the overall structure of the molecule and the $\pi$ bonds spread out over the carbon atoms. In Hückel approximation, the $\pi$ orbitals are assumed to be the combination of the atomic orbitals of the carbon atoms which are involved in conjugation of $\pi$ bonds.