Aromatic Compounds 6.1.1

Question 1

what is Benzene?

Answer 1

A hydrocarbon with a cyclical structure.

C6H6

Question 2

What was the Kekule Structure?

Answer 2

Plannar cyclical structure
Alternating C-C and C=C bonds
H’s pointing outwards

Question 3

What are problems with the Kekule Structure?

Answer 3

The carbon carbon bonds were all the same length in benzene, but C-C and C=C bonds are different lengths.
Benzene doesn’t behave like an alkene, doesn’t easily undergo addition reactions.
Benzenes hydrogenation value is less exothermic than expected, showing benzene is more stable than expected.

Question 4

What is the Delocalised model of Benzene?

Answer 4

It has benzene as a hexgonal carbon structure, with the P orbitals of the carbons being delocalised in rings above and below the carbons. 3 Electrons above, 3 electrons below.

Question 5

What is the resonance hybrid model of benzene?

Answer 5

It is the kekule model however the double bonds and single bonds switch at such high frequency they appear as the delocalised model.

Question 6

What is Electrophilic Substitution?

Answer 6

When a Powerful electrophile switches places with a atom or branch within the molecule.
eg. Nitration of Benzene or Halogenation or Friedel Craft

Question 7

What are the Reagents and Conditions for the Nitration of Benzene?

Answer 7

Reagents:
Concentrated Nitric Acid
Concentrated Sulphuric Acid (catalyst)
Conditions:
Reflux
55°C

Question 8

What is the Nitronium ion?

Answer 8

NO2+

It is a Powerful electrophile used for the nitration of benzene.

Question 9

What is the equation for the production of Nitronium Ion?

Answer 9

H2SO4 + HNO3 → HSO4- + NO2+ + H2O

Question 10

What is the Equation for the Nitration of Benzene?

Answer 10

C6H6 + HNO3 → C6H5NO2 + H2O

Question 11

How is H2SO4 a Catalyst in the Nitration of Benzene?

Answer 11

H2SO4 becomes HSO4- , and the second H reacts with HNO3 to becom Water and NO2+.
NO2+ and a H in the benzene switch place, the H+ from the Benzene reacts with HSO4- to produce H2SO4.

Question 12

What are uses of the Nitration of Benzene?

Answer 12

Production of Dyes and explosives.

Question 13

What are the Reagents and Conditions required for Halogenation of Benzene?

Answer 13

Reagents:
Chlorine
Halogen Carrier (catalyst)
Conditions:
Reflux in presence of a halogen carrier.

Question 14

Why is a Halogen Carrier needed for Halogenation of Benzene?

Answer 14

Because Halogen moleules are non-polar.

The Halogen carrier polarises the molecule.

Question 15

What is the Equation of the Halogen and the Halogen Carrier?

Answer 15

Cl2 + FeCl3 (Or AlCl3) → FeCl4- (Or AlCl4-) + Cl-

Question 16

What is the Equation for the Halogenation of Benzene?

Answer 16

C6H6 + Cl2 → C6H6Cl + HCl

Question 17

Where do the Curly arrows go in Electrophilic substitution of Benzene?

Answer 17

Step one)
From Ring to Electrophile
Step two)
From Hydrogen (the one on the same carbon as the electrophile) to +

Question 18

What is a Friedel Craft Reaction?

Answer 18

When a C-C bond is formed with a Benzene.

Question 19

What are the two types of Friedel Craft Reactions?

Answer 19

Acylation:
When an acyl group is substituted in to a benzene ring.
Alkylation:
When a alkyl group is substituted in to a Benzene ring.

Question 20

What are the Reagents and Conditions of Alkylation?

Answer 20

Reagents:
Alkyl Chloride (RCl)
Halogen Carrier (Catalyst)
Conidtions:
Anhydrous (dry)

Question 21

What is the Equation for Alkylation?

Answer 21

C6H6 + RCl → C6H5R + HCl

eg(C6H6 + CH3Cl → C6H5CH3 + HCl)

Question 22

What are the Reagents and conditions for Acylation?

Answer 22

Reagents:
Acyl Chloride
Halogen Carrier (catalyst)
Conditions:
Anhydrous

Question 23

What is an Alky Group?

Answer 23

An Alkane that is missing a Hydrogen.

eg CH3+

Question 24

What is a Acyl Group?

Answer 24

An Alkyl group containing a C=O bond.

eg CH3CO+

Question 25

What is the Equation for Acylation?

Answer 25

C6H6 + RCOCl → C6H5COCl + HCl

eg(C6H6 + CHCOCl → C6H5COCL + HCl)

Question 26

What is the Equation for the creation of an Electrophile used in Friedel Craft Reactions?

Answer 26

Alkyl: Catalyst + Alkyl Chloride → Alkyl + Catalyst Chloride
eg(FeCl3 +CH3Cl → CH3+ + FeCl4-)
Acyl: Catalyst + Acyl Chloride → Acyl + Catalyst Chloride
eg(AlCl3 + CH3COCl → CH3CO+ + AlCl4-)

Question 27

What is a Phenol?

Answer 27

A Benzene Ring with an OH group instead of onme of the H’s.
It is an almost colourless crystalline solid.
They are very weak acids, can react with metals and hydroxides but not carbonates.
C6H5OH

Question 28

How does Phenol react with Sodium Hydroxide?

Answer 28

C6H6OH (aq) + NaOh (aq) → C6H5O-Na+ (aq) + H2O

Question 29

How does Phenol react with Sodium?

Answer 29

2(C6H5OH) (s) + 2Na (s) → 2(C6H5O-Na+) (s) + H2 (g)

Question 30

What is the Activation of a Benzene Ring?

Answer 30

When a species attaches to a Benzene ring its lone pair can merge with the delocalised rings of the Benzene.
Making the rings more negative(activated), therefore more reactive with electrophiles.

Question 31

What is the Bromination of Phenol?

Answer 31

When Phenol reacts with Bromine water.
The reaction does not require a Catalyst or Halogen Carrier.
C6H5OH + 3Br2 → C6H5OHBr3 (2,4,6-Tribromophenol) + 3HBr

Question 32

What is the Nitration of Phenol?

Answer 32

When Nitric Acid reacts with Phenol.
The reaction does not require a catalyst.
C6H5OH + HNO3 (Concentrated) → C6H5OH(NO2)3 (2,4,6-Trinitrophenol)
C6H5OH + HNO3 (Weak) → C6H5OH(NO2)3 (2-Nitrophenol)

Question 33

What are 2- and 4- Directing Groups?

Answer 33

Positions on the Phenol where certain molecules preferance when reacting in 2,4 positions. (also 6 however symetry)
They donate electrons into the ring, increasing the reactivity of Phenol.
eg OH and NH2

Question 34

What are 3- Directing Groups?

Answer 34

Positions on the Phenol where certain molecules preferance when reacting in 3 position. (also 5 however symetry)
They withdraws electrons from the ring, decreasing the reactivity of Phenol.
eg NO2