3.3.10.2 Electrophilic Substitution

Question 1

What reactions does benzene undergo?

Answer 1

It only undergoes substitution, not addition

Question 2

What can the NO2 be replaced by in nitrobenzene?

Answer 2

Any electrophile

Question 3

What are friedel - crafts acylation reactions?

Answer 3

When AlCl3 is added

Question 4

What do activating groups do?

Answer 4

Activate the ring

Question 5

What do deactivating groups do?

Answer 5

Deactivate the ring

Question 6

At what rate is the second and third NO2 group added?

Answer 6

2nd: added slower because electron density is pulled towards the withdrawing group
3rd: slower ^ ^ ^ ^ ^ ^ ^

Question 7

What is the nucleophile for nitration?

Answer 7

+ NO2

Question 8

What is the nucleophile for acylation?

Answer 8

+
C = O
|
R

Question 9

What is the nucleophile for halogenation?

Answer 9

X2

Question 10

What is the nucleophile for addition?

Answer 10

H2

Question 11

What is the nucleophile for alkalation?

Answer 11

+CH3

Question 12

Why does benzene burn with a sooty flame?

Answer 12

It has a high carbon to hydrogen ratio

This leaves unburnt carbon which produces soot

Question 13

Why does benzene undergo electrophilic substitution and not addition?

Answer 13

Addition would require enough energy to destroy the aromatic system

Question 14

What is the mechanism for the electrophilic substitution of arenes?

Answer 14

See card

Question 15

What are the Friedel-Crafts acylation reactions?

Answer 15

Aluminium chloride acts as a catalyst
RCO substitutes with a hydrogen
Acyl chlorides provide the RCO group

Question 16

What is an electrophile?

Answer 16

A positive ion or the positive end of a dipole

Question 17

What are the electrons in a benzene ring attracted to?

Answer 17

Electrophiles (positive)

Question 18

What is the nitration reaction of arenes?

Answer 18

The substitution of an NO2 group for one of the hydrogen atoms
The NO2+ electrophile is generated by concentrated nitric and sulfuric acids
Sulfuric acid donates a proton to HNO3 to form H2NO3
H2NO3 then loses a molecule of water to give NO2 (nitronium or nitryl cation)

Question 19

What are examples of electron withdrawing groups?

Answer 19

NO2, COCl

Question 20

What are examples of electron releasing groups?

Answer 20

CH3, OCH3, OH, NH2

Question 21

What are electron withdrawing groups and what do they do?

Answer 21

They withdraw electrons from the ring, making it less susceptible to further electronic substitution
They direct further substitution to the 3rd and 5th positions

Question 22

What are electron releasing groups and what do they do?

Answer 22

They release electrons onto the benzene ring and therefore make it more susceptible to further electrophilic substitution reactions
They direct further substitution to the 2nd, 4th and 6th positions on the ring

Question 23

What are the Friedel crafts acylation reactions?

Answer 23

Aluminium chloride catalyst

Substitution reaction with an RCO group substituting for a hydrogen on the aromatic ring

Question 24

How is the nitrate ion formed from sulfuric and nitric acids?

Answer 24

HNO3 + 2H2SO4 = NO2+ + H3O+ + 2HSO4-

Question 25

What are the friedel craft reactions of methylbenzene?

Answer 25

C6H5 CH3
  Cl2 + UV
C6H5 CH2 Cl
  KCN: aqueous and alcoholic
C6H5 CH2 CN
  Hydrogen or nickel
C6H5 CH2 CH2 NH2