Benzene Flashcards

1
Q

Evidence to disprove kekules structure

A

Lack of reactivity (doesn’t undergo electrophilic addition)- no reaction with bromine water
Benzene bond lengths all same
Hydrogenation 3x cyclohexene only -208kjmol-1

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2
Q

Delocalised model of benzene

A

adjacent p orbitals overlap sideways below and above the plane creates pi bonds forming ring of electron density
Delocalised ring

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3
Q

Phenol as an acid

A

Less soluble in water due to presence of non polar benzene ring
Ability to partially dissociate to produce h+ ions and Phenoxide ion

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4
Q

Why are phenols more reactive than benzene

A

Increased reactivity caused by lone pair of e- in oxygen p orbital donated into the pi system - electron density increases and attracts electrophiles more strongly

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5
Q
  • nh2 directing
A

2,4,6

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6
Q

-no2 directing

A

3

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7
Q

-OH directing

A

2,4,6

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8
Q

Halogen directing

A

2,4,6

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9
Q

-cooh directing

A

3

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10
Q

CN directing

A

3

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11
Q

Benzene ring attached to 7 or more carbon chain or alkyl chain w func group

A

A substitutent
Prefix is phenyl

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12
Q

Reactions of benzene

A

Substitution reactions
Benzene reacts w electrophiles
Electrophilic substitution

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13
Q

Nitration of benzene

A

Reacts w nitric acid conc
H2SO4 and 50 degrees
Forms nitrobenzene and water
HNO3 + H2SO4=>NO2+ + HSO4- + H2O

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14
Q

Halogenating of benzene

A

Halogen carrier required to react
Electrophilic substitution
Benzene too stable to react w Br2
Br2 + FeBr3 => FeBr4- + Br+
Bromobenzene and H+ form
FeBr4- + H+ => FeBr3 + HBr

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15
Q

Alkylating of benzene

A

AlCl3 acts as catalyst
Haloalkane with AlCl3 forms electrophile
Forms HCl and xxthylbenzene

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16
Q

Acylation of benzene

A

Electrophilic sub of acyl chloride
Requires halogen carrier to form an electrophile
Forms phenylxxanone and HCl

17
Q

Phenols

A

OH group attached to benzene ring

18
Q

Phenol weak acid reactions

A

+NaOH
Forms Sodium phenoxide salt and H2O

19
Q

Bromination of phenol

A

Br2 (aq)
Forms white pp = 2,4,6- tribromophenol and 3HBr
Orange to colourless

20
Q

Nitration of phenol

A

With HNO3 dilute
Forms 2/4-nitrophenol and water