Chapter 14, Problem 14.5YT

Interpretation Introduction

Interpretation:

The carbon-carbon bond lengths in ethane and ethene are to be compared to those in cyclobutadiene.

Concept introduction:

The normal bond length of carbon-carbon single bond is $\text{154 pm}$ while that for carbon-carbon double bond is $\text{132 pm}$. In cyclic conjugated compounds, due to resonance stabilization, carbon-carbon bond length of single bond significantly shows double-bond character and is substantially shorter than a normal carbon-carbon single bond and longer than a normal double bond.