4.2 Aromatic compounds

Question 1

What evidence disproves Kekules structure?

Answer 1

• Undergoes electrophilic substitution with bromine not electrophilic addition
  *Enthalpy of hydrogeneration is lower than expected
  *Has intermediate carbon to carbon bonds

Question 2

What are the key points in the structure of benzene?

Answer 2

*trigonal planar around each C
*120
*Sigma bonds between C-H and H-H
*3 bonded pairs, no lone pairs
*Delocalised Pi ring- p orbital overlap

Question 3

What is the overall reaction of the nitration of Benzene?

Answer 3

Benzene + HNO3 —-> Nitobenzene + H2O

Question 4

What are the conditions and catalyst for nitration of benzene?

Answer 4

55*C and sulfuric acid (H2SO4)

Question 5

Three steps in synthesis of Nitrobenzene

Answer 5

1.Formation of electrophile (NO2+)
2. Electrophilic substitution
3.Reformation of catalyst (H2SO4)

Question 6

What catalyst is used in aliphatic esterification?

Answer 6

sulfuric acid (H2SO4)

Question 7

What catalyst is used in aromatic esterification?

Answer 7

None

Question 8

CH3CH2Cl + NaOH (aq) —->

Answer 8

CH3CH2OH + NaCl

Question 9

CH3CH2Cl + NaOH (acl) —>

Answer 9

CH2CH2OH
+ NaCl

Question 10

Why are aromatic compounds resistant to addition reactions?

Answer 10

As they require the stable ring to break, so instead react by elimination

Question 11

Why does AlBr3 cause an electrophilic elimination

Answer 11

It is electron deficient and so induces a dipole in Br2

Question 12

Is C-Cl bond stronger and shorter in aromatic or aliphatic? + why?

Answer 12

In aromatic due to p-orbital overlap and the bonds repelling nucleophiles