Aromatic Chemistry

Question 1

Structure of benzene

Answer 1

Each bond has an intermediate length between that of a double and single bond. The outer electron from the p-orbital of each carbon atom is demoralised to form the central ring. The ring structure makes benzene very stable compared to other molecules of a similar size.

Question 2

Properties of arenes (aromatic compounds)

Answer 2

High melting points due to the high stability of the delocalied ring but low boiling points as they are non-polar molecules and often cannot dissolve in water.

Question 3

Electrophilic substitution description

Answer 3

Delocalised ring in benzene is an area of high elextron density making it susceptible to attack from electrophiles. Species attack ring and partially destroy then restore the ring. Mechanism allows Amines and nitrobenze to be formed from benzene.

Question 4

Formation of nitrobenzene conditions

Answer 4

NO²,+ ion electrophile. Produced in the reaction of conc sulfuric acid and conc nitric acid (HNO³).
When heated with benzene at 55°C. At higher temp multiple substitutions occur for the production of aromatic Amines.

Question 5

Friedal-Crafts Acylation description

Answer 5

Delocalised electron ring acts as a nucleophile and attacks acyl chloride.

Question 6

Friedal-Crafts Acylation conditions

Answer 6

Reactive intermediate formed from acyl chloride and an aluminium chloride catalyst. At the end of the reaction H+ removed to reform the catalyst.
R-COCl + AlCl³ -> R-CO+ + AlCl⁴-