Aromaticity

Question 1

What are the requirements for aromaticity?

Answer 1

The molecule must be cyclic Planar Conjugated (alternating sig and pi bonds) Obeys Huckel’s Rule

Question 2

What is huckels rule and what does it mean?

Answer 2

4n+2, This means that we will only find pi electrons in 2, 6, 10, 14, 18, etc for aromatic compounds. ‘n’ is NOT a components of the molecule so do not go looking for it. You will never find aromatic molecules with pi electrons adding up to 0, 1, 3, 4, 5, etc.

Question 3

Aromatic or Nah?

Answer 3

This is benzene. It is cyclic, planar, conjugated, and has 6 p orbital electrons. With 6 p electrons, it obeys huckels rule.

Question 4

Aromatic or Nah?

Answer 4

To qualify as aromatic, a compound must be cyclic, planar, conjugated (alternating pi and sigma bonded atoms), and obey Huckel’s rule (i.e., the molecule must have a total of 4n+2 π electrons). It does not satisfy Huckel’s rule- it has 4 electrons in p orbitals and there is a discontinuity at the top of the molecule as drawn.

Question 5

Aromatic or Nah?

Answer 5

This is naphthalene. It is cyclic, planar, conjugated, and has 10 p orbital electrons.

Question 6

Aromatic or Nah?

Answer 6

This is pyrrole. It is cyclic, planar, conjugated, and has 6 p orbital electrons (counting the lone pair on the nitrogen).