18. Aromaticity

Which of the following are aromatic?

a.

b.

c.

Which ion in each of the following pairs is more stable?

d.

(i) Classify the following molecules as aromatic, nonaromatic, or antiaromatic.

(ii) For the aromatic and antiaromatic molecules, solve for n in Hückel’s/Breslow’s rule. For the other molecules, explain which of the rules of aromaticity is being broken.

(b)

The following molecules and ions are grouped by similar structures. Classify each as aromatic, antiaromatic, or nonaromatic. For the aromatic and antiaromatic species, give the number of pi electrons in the ring.

(c)

One of the following compounds is much more stable than the other two. Classify each as aromatic, antiaromatic, or nonaromatic.

Which of the following is an aromatic hydrocarbon?

Which of the following is primarily composed of $\mathrm{aromatic} \mathrm{hydrocarbons}$?

Which ion in each of the following pairs is more stable?

a.

(i) Classify the following molecules as aromatic, nonaromatic, or antiaromatic.

(ii) For aromatic molecules, solve for n in Hückel’s rule. For all other molecules, explain which rule of aromaticity is being broken.

(c)

How would you convert the following compounds to aromatic compounds?

(a)

(b)

(c)