Aromatic Chemistry

Question 1

Define Aromatic Compounds

Answer 1

Organic compounds with 1 or more Benzene ring

Question 2

Define Benzene

Answer 2

Aromatic compound with 6 C atoms, 6 H atoms & ring of delocalised e-

Question 3

Outline the bond lengths of:
C-C Bonds
C=C Bonds
C-C in Benzene
in nanometers

Answer 3

C-C = 0.154
C=C = 0.134
C-C (Benzene) = 0.139

Question 4

Is Benzene saturated or unsaturated?

Answer 4

Saturated - all bond lengths same

Question 5

How is the central ring of Benzene formed?

Answer 5

Outer e- from p-orbital delocalised
Ring makes Benzene stable

Question 6

What was Benzenes structure & hydrogenation enthalpy originally predicted as?

Answer 6

1. Cyclohexatriene with 3 C=C + 3C-C
2. -360kJmol-1

Question 7

Outline the actual hydrogenation enthalpy of Benzene

Answer 7

-208 kJmol-1

Question 8

Calculate the Delocalisation Stability Energy between Cyclohexa-1,3,5-triene and Benzene

Answer 8

360 - 208 = 152kJmol-1

Question 9

What’s another way of saying Aromatic Compounds?

Answer 9

Arenes

Question 10

Outline the melting and boiling points of Arenes

Answer 10

MP = high due to delocalised ring stability
BP = low due to non-polarity

Question 11

What bonding sequence do Benzene rings undergo? Why?

Answer 11

Electrophilic Substitution - e- ring has high e- density so electrophiles attack

Question 12

What happens to the e- ring during electrophilic substitution?

Answer 12

Partially destroyed then restored

Question 13

What products can form during the electrophilic substitution of benzene?

Answer 13

Nitrobenzene and Aromatic Amines

Question 14

Outline the electrophile for the electrophilic substitution to form Nitrobenzene and how it’s formed.

Answer 14

NO2+ ion
Formed in the reaction H2SO4 + HNO3

Question 15

Outline the reaction for the formation of the nitrobenzene electrophile

Answer 15

H2SO4 + HNO3 -> H2NO3+ + HSO4-
H2NO3+ -> H2O + NO2+

Question 16

How does Nitrobenzene form?

Answer 16

NO2+ electrophile replaces a H+ ion

Question 17

What’s the condition for a mono-substitution of Nitrobenzene to occur?

Answer 17

55 degrees Celsius - above causes multiple

Question 18

How do you normally name Aromatic Compounds?

Answer 18

Prefix = whatever is bonded to the ring (e.g bromo-, nitro-)
Suffix = -benzene
(e.g: Bromobenzene)

Question 19

What are exceptions to naming aromatic compounds?

Answer 19

C6H5OH = Phenol not Hydroxybenzene
C6H5NH2 = Phenylamine not Aminobenzene

Question 20

What reaction type is turning Nitrobenzene into Phenylamine compounds?

Answer 20

Reduction

Question 21

Outline the conditions for turning Nitrobenzene into Phenylamine compounds

Answer 21

NaOH (aq)