Aromatic Chemistry

Question 1

Benzene Structure

Answer 1

C6H6, 6 carbon atoms in a Hexagonal Planar Ring

Each C bonded 2C and 1H
Each C has p electron - not bonded

Question 2

Explain pi-delocalised system

Answer 2

P orbitals containing p electrons can overlap forming a pi-delocalised system above and below the main ring

Question 3

Formation delocalised system

Question 4

Why is model with delocalised electrons most appropriate

Answer 4

•c-c in benzene all same length
•energy released when 1 mol of benzene is hydrogenated should be 3 times energy released to hydrogenate cyclohexane if Kekule correct - NOT TRUE

Question 5

What is benzene obtained from

Answer 5

Petroleum(crude oil)

Question 6

What state is Benzene at room temp and pressure

Answer 6

Colourless liquid

Question 7

What does the circle in Benzene represent

Answer 7

Delocalised pi cloud of electrons
6 electrons

Question 8

What does delocalisation mean

Answer 8

Electrons are spread over several atoms

Question 9

What reactions does Benzene not undergo easily and why

Answer 9

Addition
Stability of pi delocalised sys

Question 10

Does Benzene react readily with Bromine?
What does?

Answer 10

No
Alkenes

Question 11

What reactions does Benzene undergo

Answer 11

Electrophilic Substitution

Question 12

Benzene with OH

Answer 12

Phenol

Question 13

Benzene with CH3

Answer 13

Methylbenzene
or Toluene

Question 14

Benzene with NH2

Answer 14

Phenylamine

Question 15

Benzene with COOH

Answer 15

Benzoic Acid

Question 16

Benzene with N2Cl

Answer 16

Benzene Diazonium Chloride

Question 17

Benzene with COOCH3

Answer 17

Methyl Benzoate

Question 18

3 steps of formation of electrophile for Nitration of Benzene

Answer 18

1: HNO3 + H2SO4 -> H2NO3+ + HSO4-

2: H2NO3+ -> NO2+ + H2O

3: H2O + H2SO4 -> H3O+ + HSO4-

Question 19

Electrophile of Nitration and its formation

Answer 19

NO2+ , Nitronium Ion

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

Question 20

Equation for Nitration Of Benzene

Answer 20

C6H6 + HNO3 -> C6H5NO2 + H2O
NO2+. H+
Nitrobenzene product

Question 21

What is used instead of Benzene in schools and why

Answer 21

Methyl Benzoate ester
Benzene is toxic

Question 22

Mechanism For Nitration Methyl Benzoate

Answer 22

Arrow from circle to NO2+

NO2+ and H bonded
Half circle with +
Arrow from H bond to +

Product + H+

Question 23

Monohalogenation of Benzene

Answer 23

Monobromination in presence of iron/iron (III) bromide FeBr3

FeBr3 over arrow
Bromobenzene + HBr

Question 24

Mechanism Monohalogenation Benzene

Answer 24

Arrow from circle to Br
Arrow from Br-Br bond to FeBr3

H and Br bonded
Half circle with +
Arrow from H bond to +
FeBr4- beside

Product H+ and FeBr4-

HBr + FeBr3

Question 25

What does FeBr3 act as in Monobromination

Answer 25

Halogen Carrier

Question 26

What are the Two Friedal Crafts Reactions

Answer 26

Allylation and Acylation

Question 27

What are the 3 Stages of **Alkylation**

Answer 27

1: AlCl3 reacts with HalogenoAlkane to form Electrophile (H2C+CH3) 2: Reaction of Electrophile with Benzene 3: Regeneration of Catalyst AlCl4- + H+ -> AlCl3 + HCl

Question 28

Alkylation

Answer 28

Benzene react with Chloroethane in presence of AlCl3 to form Ethylbenzene C6H6 + CH3CH2Cl -> C6H5CH2CH3 + HCl

Question 29

Acylation

Answer 29

Acyl halide in presence of an Aluminium Halide e.g. C6H6 + CH3COCl -> C6H5COCH3 + HCl

Question 30

3 Stages of **Acylation**

Question 31

3 Stages of **Acylation**

Answer 31

1: Form Electrophile CH3COCl + AlCl3 -> CH3O+ + AlCl4- 2. Electrophile + Benzene 3. Regeneration of catalyst AlCl4- + H+ -> AlCl3 + HCl

Question 32

Multiple Substituted Benzene Compounds Naming

Answer 32

Highest Priority group given position 1 Other groups numbered accordingly Alphabetically

Question 33

Fused Benzene Ring Examples

Answer 33

Naphthalene, C10H8 2 hexagons Anthracene, C14H10 3 hexagons

Question 34

Reactivity Benzene vs Alkene

Answer 34

Benzene ~ Electrophilic **Substitution** Stability pi delocalised electrons can overlap system Alkenes ~ Electrophilic **Addition** Pi bond is broken