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aromatic chemistry Flashcards

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1
Q

what is aromatic chemistry

A

the study of benzene and compounds containing the benzene ring

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2
Q

what are compounds containing the benzene ring called

A

arenes

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3
Q

evidence against the kekule structure of benzene

A
  • benzene doesn’t decolourise bromine water (whereas c=c does)
  • carbon carbon bond lengths (C=c shorter than C-C)
  • thermochemical data for the hydrogenation of benzene suggests that more stable than the kekule structure
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4
Q

justfifcation for c-c bond lengths in benzene

A

bond lengths intermediate- benzene is a regular hexagon- if bonds single double alternating would be irregular

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5
Q

how does thermochemical data for hydrogenation of benzne suggest its more stable than expected

A

enthalpy is roughly 150kJ/mol more stable than expected

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6
Q

what structure does benzene have

A

a regular, planar, hexagon structure

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7
Q

why does benzene have a regular planar hexagon structure

A

the six c atoms and the six h atoms are all in the same plane

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8
Q

what are all bond angles in benzene

A

120 degrees

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9
Q

how are the 6 c-c bond intermediate in length

A

between length of a c-c and a c=c bond

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10
Q

how does the pi bond form

A

overlap of adjacent p orbitals

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11
Q

where does the pi bond form

A

above and below the ring

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12
Q

what is the pi bond essentially

A

an electron cloud above and below the ring

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13
Q

where are elections In the pi bond

A

delocalised

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14
Q

why are the pi bonds in benzene harder to break than a normal c=c bond

A

the delocalised structure has extra stability

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15
Q

which part of the benzene ring attracts electrophile

A

the pi bond above and below the plane

is an area of moderately high electron density

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16
Q

electrophile

A

an electron pair acceptor

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17
Q

what happens in the electrophilic substitution reaction of benzene

A

a h atom from the benzene ring is replaced by a new group of atoms

18
Q

why does benzene undergo substitution rather than addition

A

to preserve the stability of the delocalised pi bond

19
Q

nitration:reagents

A

conc sulphuric and conc nitric

sulphuric is catalyst

20
Q

nitration: conditions

A

below 50 degrees Celsius

21
Q

nitration: overall equation

A

benzene+ nitric > nitrobenzene + water

22
Q

nitration: electrophile

A

nitronium ion NO2+

23
Q

nitration: generation of electrophile equation

A

H2SO4 + HNO3 > NO2+ + HSO4- + H2O

24
Q

nitration: regeneration of catalyst

A

H+ + HSO4- > H2SO4

25
Q

acylation: reagents

A

acyl chloride

26
Q

acylation: conditions

A

AlCl3 (halogen carrier) and heat

27
Q

acylation: general equation

A

benzene + acyl chloride > (benzene)-COR + HCl

28
Q

acylation: electrophile

A

RCO +

29
Q

acylation: benzene + ethanoyl chloride

generation of electrophile

A

CH3COCl + AlCl3 > CH3CO+ + AlCl4-

30
Q

acylation: benzene + ethanoyl chloride

regeneration of catalyst

A

AlCl4- + H+ > AlCl3 + HCl

31
Q

reaction mechanism cyclohexene and bromine

A

electrophilic addition

32
Q

reaction mechanisms benzene and bromine

A

electrophilic substitution

33
Q

why are the reactions different: benzene

A
  • delocalised pi bonds
  • lower electron density
  • need to generate Br+ for the reaction to occur
34
Q

why are the reactions different: cyclohexene

A
  • localised pi bonds
  • greater electron density
  • able to induce dipole in Br2
35
Q

why is methyl benzene more reactive than benzene with electrophiles

A
  • CH3, through positive inductive effect, provides more electron density
  • increases electron density of delocalised pi bond
  • methyl benzene better at attracting electrophiles
36
Q

why is the nitration of benzene an important reaction

A

nitrogen containing aromatic compounds have many applications

37
Q

uses of nitrobenzene

A

explosives

38
Q

reagents for nitration of benzene

A

conc nitric and conc sulphuric

39
Q

uses of benzene with -NH2 group attached (amine)

A

dyes and drugs

40
Q

how to get from nitrobenzene to benzene with an -NH2 group (amine)

A

conc hydrochloric

tin catalyst

41
Q

what can nitrobenzene be reduced to form

A

amine

42
Q

equation for reduction of aromatic nitro compounds

A

benzene-NO2 + 6[H] > benzene-NH2 + 2H2O

Chemistry (42 decks)

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