Arenes

Question 1

how to form halogenoarene

Answer 1

1. react arene with pure halogen
2. anhydrous AlCl3 or FeCl3 catalyst (depends on the halogen)

Question 2

nitration of arene

Answer 2

1. concentrated HNO3 and H2SO4
2. temperature 25 - 60 C

Question 3

Friedel-Crafts alkylation

Answer 3

1. CH3Cl (haloalkane)
2. AlCl3
3. heat
4. also produce HCl (hydrogen halide)

Question 4

Friedel-Craft’ acylation

Answer 4

1. CH3COCl (acyle halide)
2. AlCl3 catalyst
3. heat
4. also produce HCl (hydrogen halide)

Question 5

what are the electron donating group that activates 2,4,6

Answer 5

1. OH
2. NH2
3. CH3

Question 6

hydrogenation

Answer 6

1. H2
2. Ni/Pt catalyst
3. cyclohexane ring

Question 7

why is C-halide bond stronger in arene

Answer 7

lone pair of halide overlap with delocalised π bonds of benzene

Question 8

when halogenation happens on the side chain of methyl-benzene

Answer 8

1. UV light leads to free-radical substitution of side chain alkane rather than electrophilic substitution of ring
2. boil needed

Question 9

what is produced with halogenation of methyl-benzene

Answer 9

1. mixutre of 2-bromo and 4-bromo (must draw both)
2. in excess 2,4,6 -bromo

Question 10

the mechanism of formation of nitrobenzene and bromobenzene

Answer 10

see in diagram note

Question 11

what are electron withdrawing groups that deactivate 2,4,6 therefore 1,3,5

Answer 11

1. NO2
2. COOH
3. COOR

Question 12

oxidation of R-benzene

Answer 12

1. side chain can be completely oxidised by KMnO4
2. add dilute acid to give benzoic acid
3. reflux

Question 13

why electrophilic substitution rather than addition

Answer 13

substitution preserves the aromatic structure but addition destroys it
=> more energy needed for addition
=> favoured due to aromatic stabilisation provided by the delocalised π-bonds

Question 14

halogenoalkane and halo benzene which is more reactive

Answer 14

1. halogenoalkane is more reactive
2. partial double bond due to the delocalised electron system of benzene stablised