Benzenes

sp2

hybridization of benzenes

1. sp2 hybridization

2. planar/ flat

3. cyclic

4. conjugated

5. aromacity

6. follows Huckle’s rule

Characteristics of benzene

Huckle’s rule

states that a planar, fully conjugated, cyclic molecule is aromatic if it contains 4n + 2

4n=(pi)(e-)

anti-aromatic

electrophilic aromatic substitution (EAS)

A reaction where an electrophile replaces a hydrogen on a benzene ring.

A substitution pattern on aromatic ring

NO₂⁺ (nitronium ion).

the electrophile in nitration?

To keep aromatic stability.

Why does benzene undergo substitution instead of addition?

Hydrogen (H)

In EAS, what is replaced on benzene?

Cl⁺ or Br⁺

the electrophile in halogenation

Ortho, Meta, Para

position naming of the two groups in a disubstituted aromatic ring

Ortho (-o)

1,2 position

Meta (-m)

1,3 position

Para (-p)

1,4 position

1. phenol

2. benzaldehyde

3. benzoic acid

3 IUPAC recognized parent names when naming

trinitrotoluene or TNT

Halogenation

Possible reaction that can happen in Benzenes

Halogenation

where a hydrogen atom on the benzene ring is replaced by a halogen (Cl, Br)

in the presence of a Lewis acid catalyst (FeCl3, FeBr3, AlCl3, AlBr3).

This reaction produces aryl halides (e.g., chlorobenzene, bromobenzene)

amylmetacresol a.k.a strepsils

“amyl”

a 5C chain

1. catechol

2. resorcinol

3. hydroquinone

di-hydroxy benzenes

1. naphthalene

2. anthracene

3. phenanthrene

Multi-benzene structures

Cyclopentanoperhydrophenanthrene ring

A fused four-ring structure (3 hexane rings + 1 pentane ring) that forms the basic steroid nucleus found in compounds like cholesterol, steroid hormones, and bile acids.