Reactions of Haloarenes

Question 1

why are haloarenes less reactive towards nucleophilic substitution?

Answer 1

1.the C-X acquires partial double bond character through resonance which is difficult to break.
2.halogen is attached to sp2 carbon atom which is more electronegative due to more s character so the bond length would be shorter and harder to break.
3.the phenyl cation is unstable so sn1 mechanism is ruled out.
4.due to repulsion between electron rich arenes and electron rich nucleophiles.

Question 2

how can chlorobenzene be converted to phenol?

Answer 2

at 623K, NaOH and 300 atm

Question 3

how can we increase the reactivity of haloarenes and where

Answer 3

presence of electron withdrawing groups like -NO2 at ortho and para positions.

Question 4

halogenation

Answer 4

requires anhydrous fecl3 (para is major)

Question 5

nitration

Answer 5

haloarene + hno3 and h2so4 to form para and nitro chloro benzene

Question 6

sulphonation

Answer 6

conc.h2so4 and heat to give so3h attached to chlorobenze

Question 7

electrophilic substitution reactions

Answer 7

1.halogenation
2.nitration
3.sulphonation
4.friedal crafts reactions

Question 8

friedal crafts alkylation

Answer 8

chlorobenzene + ch3cl in the presence of anhydrous alcl3

Question 9

friedal crafts acylatio

Answer 9

chlorobezene + ch3cocl to form chloroacetophenone.

Question 10

Wurtz-Fittig reaction

Answer 10

alkyl halide + aryl halide + 2Na in dry ether gives alkylarene

Question 11

Fittig reaction

Answer 11

2aryl halide + 2Na in dry ethergives two alkyl groups joined together + 2NaX