ORGANIC CHEMISTRY II CHEM 2325

AROMATICITY - BENZENE

Aliphatic and Aromatic Compounds

Aromatic - fragrant

benzene and compounds which resemble benzene in chemical behavior

Aromatic hydrocarbons are characterized by a tendency to undergo heterolytic substitution.

Structure of Benzene

Reactions of Benzene

1. Nitration

2. Sulfonation

3. Halogenation

4. Friedel-Craft Alkylation

5. Oxidation

Stability of Benzene Ring

The heats of hydrogenation and combustion of benzene are lower than expected. This make benzene more stable than expected.

Resonance Structure of Benzene

The bond lengths between carbons is really between that of a single and a double bond.

Nomenclature of Benzene Derivatives

Monosubstituted derivatives

Disubstituted derivatives (ortho, para, meta)

Ortho is where the two groups are next to each other on the benzene ring.

 

 

 

 

Meta is where the two groups are one carbon away from each other on the benzene ring.

Para is where the two groups are two carbon away from each other on the benzene ring.

If the two substituted groups are not attached to a commonly named benzene derivative (example: toluene, phenol, aniline, etc), give the position of the two disubstituted groups in relationship to each other (ortho, meta, para), then list the substituted groups in alphabetical order followed by benzene.

 

Using the IUPAC method, if the two substituted groups are not attached to a commonly named benzene derivative (example: toluene, phenol, aniline, etc), give the position of the two disubstituted groups in relationship to each other using numbers in which the first group alphabetically becomes number 1, then list the substituted groups in alphabetical order followed by benzene.

If the one substituted group is attached to a commonly named benzene derivative (example: toluene, phenol, aniline, etc), give the position of the two disubstituted groups in relationship to each other (ortho, meta, para), then list the substituted group followed by named benzene derivative (example: toluene, phenol, etc).

Using the IUPAC method, If the one substituted group is attached to a commonly named benzene derivative (example: toluene, phenol, aniline, etc), give the position of the two disubstituted groups in relationship to each other using numbers in which the number 1 position is assumed to be the benzene derivative (example: toluene, phenol, etc) group, with the second substituted group getting the next lowest number.

Polysubstituted derivatives

If there is more than two substituted groups, give the lowest possible number combination, with the group which is alphabetically last as the assumed number one position.

If there is a name benzene derivative, give it the assumed number one position and number every thing else toward the lowest possible number combination. Use aphabetical in case of a tie.

Polynuclear aromatic hydrocarbons

Two aromatic rings that share a pair of carbon atoms are said to be fused.

Positions in the naphthalene ring system are designated with the prefix 1- and 2 - or using alpha - and beta - .