Aromatics

Question 1

Bonding, structure and stability of benzene

Answer 1

Bonding:
- each carbon bond bonded to 3 other atoms by covalent bonds
- spare electrons in p orbitals overlap to form a pi system
- delocalisation

Shape:
-planar
- hexagonal
- all bonds are equal lengths

Stability:
- Delta H hydrogenation of Benzene is less exothermic than the triune by 152kjmol-1
- the expected value for trainee in -360kjmol-1
- benzene is more stable

Question 2

What is the mechanism for benzene called

Answer 2

Electrophilic substitution

Question 3

What is the reagent and equation for Electrophilic substitution - nitration

Answer 3

Reactants : conc H2SO4 and conc HNO3
Equation: H2SO4 + HNO3 ——> HSO4- +H2O + NO2+

Question 4

Equation to reform the sulphuric acid catalyst

Answer 4

H+ +HSO4- ——> H2SO4

Question 5

Reagents for acylation of benzene - electrophilic substitution

Answer 5

Reagents: Acyl chloride and AlCl3 catalyst
Equation: CH3COCL + AlCl3 ——> CH3CO+ + AlCl4-

Question 6

Reforming the AlCl3 catalyst

Answer 6

AlCl4- + H+ ——> HCL + AlCl3