benzene and its compounds

Question 1

describe the structure and the bonding of benzene

Answer 1

-it is planar horizontal ring
-120 bond angle
-each carbon has 3 sigma bond and 1pi bond
- C-C sigma bond is sp2-sp2 orbital overlap
- C-H sigma bond is
sp2-s orbital overlap
- C-C pi bond is sideway orbital
- all C-C bond length is equal
- C atom is sp2 hybridised and has 6 delocalised electron among 6 carbon atoms
-the presence of delocalized electron makes the benzene particularly stable

Question 2

benzene undergo what kind of reaction

Answer 2

electrophilic substitution

Question 3

how is nitrobenzene formed (condition and reagent/product)

Answer 3

-by nitration
-conc. HNO3
-conc. H2SO4, 55C
(product)benzene+NO2

Question 4

how is phenylamine made from nitrobenzene (condition and reagent)

Answer 4

-by reduction
-Sn, conc. HCL and heat
-(product)benzene+NH2

Question 5

halogenation of benzene
(condition and reagent/product)

Answer 5

-with chlorine and bromine
-AlCl3 and AlBr3, rtp
(product)benzene+Cl/Br

Question 6

alkylation of benzene(condition and reagent/product)

Answer 6

-AlCl3 and heat
-(product)benzene+alkyl

Question 7

acylation of benzene(condition and reagent/product)

Answer 7

-AlCl3 and heat
(product)benzene+COCl

Question 8

addition of benzene (condition and reagent/product)

Answer 8

-addition of chlorine (UV light+heat)
-addition of hydrogen (Pt or Ni as catalyst)

Question 9

physical properties of methyl benzene

Answer 9

-bp is higher than benzene(bigger molecule so id-id force is bigger)
-mp is lower than benzene(molecules aren’t closely packed and the intermolecular force doesn’t work
well)

Question 10

chemical properties of methyl benzene

Answer 10

-more reactive (methyl is a EDG and has a +I effect so activates the ring)

Question 11

EDG examples
(2,4,6 POSITION)

Answer 11

-Cl, -CH3, -OH, -NH2,
-alkyl

Question 12

EWG examples
(3,5 POSITION)

Answer 12

-NO2, -NH3, -CN,
-COOH, -CHO, -CO CH3

Question 13

nitration of methylbenzene
(condition and reagent/product, which position)

Answer 13

-conc. H2SO4
-conc. HNO3, 55C
-2,4,6 position

Question 14

methylbenzene reaction with halogens (condition and reagent/product)

Answer 14

-with Cl2, AlCl3 and rtp, happens in ring
-with Cl2, UV light, happens in methyl group

Question 15

methylbenzene to
-COOH
(condition and reagent/product)

Answer 15

-KMnO4, OH-, H+, heat
-oxidation