Organic Chemistry

Structures and Nomenclature

Are all the carbon-carbon bonds in benzene the same length?

Yes, but you might not think so by looking at a single line structure of benzene. The actual structure of benzene is a combination of two structures, shown below. In technical terms, the electrons in the p bonds are delocalized (spread out) by resonance. The drawing convention that chemists use to represent molecular structure just can’t display this properly in a single structure. The electrons do not move from one place to another, and the carbon-carbon bonds do not oscillate between long and short—the structure is an average of these two drawings. After all, a molecule of benzene doesn’t really care that we can’t properly draw it.


Sometimes, you might see benzene drawn with a single circle in the center, representing the delocalization of the π-electrons.


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