Chapter 6, Aromatic Compounds

Question 0

How stable is benzene?

Answer 0

Benzene is more stable than expected due to the presence of delocalised electrons

Question 1

What is the structure of benzene?

Answer 1

All bond angles are 120
Each C has and ‘unused electron’
The circle represents a ring of delocalised electrons
This gives benzene areas of electron density above and below the plane of the ring

Question 2

How is the stability of benzene shown?

Answer 2

By comparing the enthalpies of cyclohexane, cyclohexa-1,3,5-triene and benzene

Question 3

What mechanism do benzene ring undergo?

Answer 3

Electrophilic Substitution

Question 4

Why does benzene undergo electrophilic substitution?

Answer 4

Because it has electron rich areas which are susceptible to attack from electrophilic.

Question 5

Why does benzene undergo substitution rather than addition?

Answer 5

In order to maintain stability

Question 6

What are the reagents for the nitration of benzene?

Answer 6

Conc nitric acid (HNO3) and conc (H2SO4)

Question 7

How is the electrophile formed for the nitration of benzene?

Answer 7

Conc H2SO4 donates a H+ to NO3 to produce NO2+ which is the electrophile

Question 8

What are nitrobenzene’s used as?

Answer 8

Explosives such as TNT

Question 9

What is another property of nitrobenzene’s?

Answer 9

They can be reduced to amines easily

Question 10

What is the type of acylation benzene rings undergo?

Answer 10

Friedel-Crafts Acylation

Question 11

What are the reagents needed for Friedal-Crafts Acylation?

Answer 11

Acyl Chloride and anhydrous aluminium chloride

Question 12

How is the electrophile formed for the Friedal-Crafts Acylation?

Answer 12

AlCl3 acts as an acid catalyst and acceptes an electron pair from Cl forming AlCl4- and electrophile CH3CO:+

Question 13

What else does Friedal-Crafts Acylation do to the product?

Answer 13

Introduces a carbonyl group and so acts as an intermediate in the synthesis of her compounds