Reactions of aromatics

Question 1

Why does benzene attract electrophiles?

Answer 1

The benzene ring is a region of high electron density

Question 2

What is an electrophile?

Answer 2

Electron pair acceptor

Question 3

What type of reaction does benzene undergo?

Answer 3

Electrophillic substitution

Question 4

Why does benzene undergo electrophilic substitution and not electrophilic addition reactions?

Answer 4

They are stable and electrophile addition would destroy the delocalised ring of electrons

Question 5

What is the first stage of the electrophilic substitution reaction?

Answer 5

The electron dense region at the centre of the benzene ring attracts an electrophile

Question 6

What is the second stage of the electrophilic substitution reaction?

Answer 6

The electrophile steals a pair of electrons from the centre of the benzene ring and forms a bond with one of the carbons

Question 7

What is the third stage of the electrophilic substitution reaction?

Answer 7

This partially breaks the delocalised electron ring and gives the molecule a positive charge

Question 8

What is the 4th stage of the electrophilic substitution reaction?

Answer 8

To regain the stability of the benzene ring, the carbon which is now bound to the electrophile, loses a hydrogen

Question 9

What is being substituted in an electrophilic substitution reaction?

Answer 9

H+ for the electrophile

Question 10

What does a nitration reaction form?

Answer 10

Nitrobenzene

Question 11

What needs to react together in order to form nitrobenzene?

Answer 11

conc. sulfuric acid and conc. nitric acid

Question 12

what is important to remember about the sulfuric acid and nitric acid?

Answer 12

They are CONCENTRATED

you wont get the mark if you forget this

Question 13

What is the equation for the reaction between concentrated nitric acid and concentrated sulfuric acid?

Answer 13

HNO₃ + H₂SO₄ -> HSO₄⁻ + NO₂⁺ + H₂O

Question 14

In a nitration reaction, what does the sulfuric acid act as?

Answer 14

Catalyst

Question 15

In a nitration reaction, what is the electrophile?

Answer 15

The nitronium ion formed

NO₂⁺

Question 16

In a nitration reaction, what do you need to make sure is maintained? Why?

Answer 16

The temperature below 55 degrees Celsius
This makes sure only one NO₂ is added
Any higher and more than one will be added

Question 17

What are uses of the nitration reaction?

Answer 17

Form aromatic amines
Dyes
Pharmaceuticals
TNT

Question 18

What does the Friedel crafts acylation add to the benzene ring?

Answer 18

Acyl group

Question 19

What is an acyl group?

Answer 19

-C(=O)-R

Question 20

What are the products of a Friedel crafts reaction?

Answer 20

HCl

Phenylketone

Question 21

In a Friedel crafts acylation reaction, how do the reactants need to be heated?

Answer 21

Under reflux in a non-aqueous solvent

Question 22

What is a halogen carrier?

Answer 22

Catalyst which makes the electrophiles stronger

Question 23

What is the halogen carrier involved in the Friedel crafts reaction?

Answer 23

AlCl₃

Question 24

What is the equation for the formation of the electrophile in the Friedel crafts reaction?

Answer 24

R-C(=O)-Cl + AlCl₃ -> R-C+=O + AlCl₄⁻

Question 25

In the Friedel crafts reaction, how does the catalyst reform?

Answer 25

the AlCl₄⁻ is attracted to the positively charged ring and one chlorine breaks off and joins with one of the hydrogens to create HCl