oat orgo unit 11

learn 1 million reactions said no reasonable person ever. The orgo teacher:

aromatic compound

compound with a fully conjugated ring system, like benzene.

• Electron density is distributed throughout the ring.

• Can be represented in hybrid form.

• Every p orbital has the same orientation.

hybrid form

3 rules of aromaticity

• The compound must be cyclic and conjugated.

  • A secondary carbocation in a ring is conjugated and sp² hybridized.

• None of the atoms in the ring can be sp³ hybridized due to bond angles.

• System must satisfy Huckel’s Rule (4n + 2 pi electrons; n = integer)

  • Benzene: 3 double bonds = 6 pi electrons. 4n + 2 = 6, so n = 1.

  • Lone pair = 2 pi electrons.

exception to aromaticity rules

If an atom has one or more lone pairs, AND is attached to an sp³ hybridized atom, then the atom is also sp³ hybridized.

antiaromatic compound

Compound is still cyclic and conjugated, as well as sp² hybridized, but does not follow Huckel’s Rule.

nonaromatic compound

Compound that breaks either rule 1 or 2 of aromaticity (cyclic and conjugated or all sp² hybridized). Rule 3 doesn’t matter.

aromaticity and acidity

• Acidic = deprotonation makes compound aromatic, because the conjugate base is more stable.

• Not acidic = deprotonation makes compound antiaromatic.

aromaticity and electrophilicity

• If loss of leaving group makes compound aromatic, compound is inclined to undergo SN1 mechanism.

• If loss of leaving group makes compound antiaromatic, compound is not inclined to undergo SN1 mechanism.

electrophilic aromatic substitution mechanism

bromination bruh

chlorination

friedel crafts alkylation

friedel crafts acylation

• Doesn’t work if a nitro group is on the benzene ring.

• Aniline also doesn’t work (NH₂ on benzene)

sulfonation

nitration

formylation

3 7q9nywb8wenq hmijggwhxeu49v

ortho, meta, and para positions

meta director

If one of the pictured substituents is already on a benzene, the other thing being added will go to the meta position.

ortho para directors

Para will be more common due to ortho’s steric hindrance.

reduction of nitro group

side chain oxidation

diazonium salt reactions

The king of aromaticity