Chapter 7 Aromatic Compounds (Part 1)

Benzene

_____________

• simplest aromatic hydrocarbon (arene)

• undergoes substitution reactions and not addition reactions, which preserves the cyclic conjugation of the ring

Benzene

the carbon-carbon bonds have the same length (139 pm); intermediate between typical single and double bonds

• single bond: 154 pm

• double bond: 134 pm

Benzene

the electron density in all six carbon-carbon bonds is identical

Benzene

Simplest Arene

Benzene

planar

all C-C-C bond angles are 120°

Benzene

all six carbon atoms are sp² hybridized

each carbon has a p orbital perpendicular to the plane of the ring

• planar

• conjugation (double bonds alternate in the ring)

• 4n+2 π

All are flat, conjugated, and n is an integer

Note: An integer is a whole number that does not include fractional or decimal parts, consisting of positive numbers, negative numbers, and zero (e.g., -5, 0, 10).

Aromaticity: Hückel 4n+2 rule

• a molecule is aromatic only if it has a ____________, monocyclic system of _____________ with a total of ____________ electrons, where n is an integer

Are these aromatic and why or why not?

Are these aromatic and why or why not?

Provide the common name.

Provide the common name.

Provide the common name.

Provide the common name.

Given the following, rank them and draw the substituents:

• benzoic acid

• benzenesulfonic acid

• ester

• acid halide

• amide

Given the following, rank them and draw the substituents:

• nitride

• aldehyde

• ketone

• phenol

• SH

• NR₂