18. Aromaticity

Make a model of cyclooctatetraene in the tub conformation. Draw this conformation, and estimate the angle between the p orbitals of adjacent pi bonds.

Despite having only sp²-hybridized carbons and having 10 electrons (4n + 2) , the annulene shown is not aromatic. Why?

Explain why each compound or ion should be aromatic, antiaromatic, or nonaromatic.

(a)

(b)

(c)

Explain why each compound or ion should be aromatic, antiaromatic, or nonaromatic.

(d)

(e)

(f) the [20]annulene dication

Classify the following compounds as aromatic, antiaromatic, or nonaromatic.

(a)

(b)