Arenes

Question 1

Physical properties of arenes

Answer 1

1. Carcinogenic & non polar
2. Soluble in non polar solvents (insoluble in polar)
3. Low MP & BP overcome weak idid

Question 2

Why Benzene undergo E sub not E add?

Answer 2

Benzene ring is resonance stabilised
(delocalised π e- cloud)
not energetically feasible to destroy

E sub not E add to preserve aromatic benzene ring structure

Question 3

Why benzene needs electrophile (partial charge not enough)

Answer 3

Delocalised π e- in benzene ring Less susceptible to electrophilic attack than C=C,
e- density is higher,
Stronger electrophile needed

Question 4

R&C nitration of Benzene (E sub)

Answer 4

Conc HNO³ conc H²SO⁴
55°C
(HNO³ + 2H²SO⁴ -> NO²+ & 2HSO⁴- & H³O+

H²SO⁴ acts as BL acid, donates H+ to HNO³
Acts as catalyst

Question 5

R&C halogenation of Benzene (E sub)

Answer 5

Cl² with anhydrous AlCl³, FeCl³, Fe

Same w Br, R&C with Br

AlX³ acts as Lewis acid (e- pair acceptor to generate electrophile X+)
Catalyst