Reactions of Aromatic compounds

Question 1

What type of reactions do arenes undergo?

Answer 1

Electrophilic substitution

Question 2

How is Nitrobenzene formed?

Answer 2

Warm benzene with warm conc. nitric acid and conc. sulfuric acid. Must keep temp. below 55 degrees Celsius.

Question 3

What electrophile is used for the nitration of benzene and how is it formed?

Answer 3

Nitronium ions (NO2+)
HNO3 + H2SO4 -> HNO3+ + HSO4-
HNO3+ -> NO2+ + SO4-

Question 4

How is Benzenesulfonic acid formed?

Answer 4

Used conc. Sulfuric acid under reflux for several hours
OR
Fuming sulfuric acid, with heat at 40 degrees for 30 mins (Reacts much quicker as there is a higher conc of SO3.)

Question 5

What is the electrophile for the sulfonation of benzene, and how is it formed?

Answer 5

Sulfur trioxide (SO3)
H2SO4 -> H2O + SO3

Question 6

Why does benzene not undergo electrophilic addition

Answer 6

Disrupts the stable ring of delocalized electrons.

Question 7

Why do halogen carriers make good electrophiles? Give examples

Answer 7

A Halogen carrier accepts a pair of electrons, which increases polarisation and sometimes forms a carbocation.
Aluminum halides, iron halides

Question 8

What makes a good electrophile?

Answer 8

Positive ions or a strong polar compound

Question 9

How does alkylation occour?

Answer 9

Deloclaised electrons are attracted to electrophile, forming a positively charged ring.
AlCl4- is attracted to the ring, and a Cl atom breaks away to bond with hydrogen.

Question 10

How does acylation occour?

Answer 10

Delocalised electrons are attracted to carbocation, breaking the ring a forming a positive charge.
Halogen carrier is attracted and Cl bonds with a hydrogen.
The acyl group attaches to benzene ring.

Question 11

How does the halogenation of benzene occour?

Answer 11

Halogen carrier polarises halogens such as Cl2, allowing the positive part of the halogen to act as the electrophile.
Hydrogen is removed and bonds with the other halogen atom.