Benzene

Question 1

Benzyl group

1. Ring with CH2NH2
2. Ring with CH2OH

Answer 1

C6H5CH2

1. Benzyl amine
2. Benzyl alcohol

Question 2

Nitration of Benzene

Answer 2

Reagent : conc HNO3
Conc H2SO4
Condition: 55
Product : Ring with NO2, nitrobenzene and H2O
( yellow liquid with almond smell)
If temp exceeds 60, then further nitration is possible produce 1,3-dinitrobenzene

Question 3

Halogenation of benzene

Answer 3

Reagent : Cl2 in CCl4
Catalyst : Anhydrous AlCl3
Condition : room temp
Product : chlorobenzene and HCl
Observation : steamy acidic fumes

Question 4

How to differentiate between benzene and cyclohexene

Answer 4

Reagent : Br2 dissolved in CCl4

Observation : cyclohexene will decolourise the brown colour of bromine while benzene does not show any change

Question 5

Friedel- Crafts alkyalation of benzene

Answer 5

Reagent : RCl ( CH3, CH3CH2)
Condition : anhydrous AlCl3, room temp
Product : ring with R + HCl
NO CL

Question 6

Friedel-Crafts Acylation of benzene

Answer 6

Reagent : RCOCl
Condition : anhydrous AlCl3, room temp
Product : Ring with RCO + HCl

Question 7

Reduction of benzene

Answer 7

Reagent : Hydrogen
Catalyst : Nickel, 180
Product : cyclohexane

Question 8

Oxidation of benzene

Answer 8

No reaction

Question 9

Mechanism of benzene

Answer 9

1. The electrophile, X+ attacks the electron rich region of the ring accepting a pair of electrons. Two of the six pie electron and the electrophile in the carbonation intermediate.
2. However, the carbonation intermediate is unstable as it has only four pie elements to be delocalised over the remaining five carbon atoms in the ring, thereby losing its stable resonance structure. Hence the carbonation will lose a H+ and the two electrons move back to the ring to form a stable resonance structure with six pie electrons delocalised over six carbon atoms again.