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Year 2 chemistry > 6.1.1 aromatic compounds > Flashcards

6.1.1 aromatic compounds Flashcards

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1
Q

what is Kekules structure for Benzene

A

C6H6

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2
Q

draw Kekules structure for Benzene and how many Sigma and Pi bonds it holds

A

12 sigma
3 pi

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3
Q

describe the evidence used to refute Kekules model of benzene
(resistant to attack from electrophiles

A

Kekules model predicts that b Benzene should undergo electrophilic addition however Benzene does not undergo electrophilic addition and is resistant to attack from electrophiles EGHBR

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4
Q

describe the evidence used to refute Kekules model of benzene
(enthaply of hydrogenation)

A

the enthalpy change of cyclohexene is -120 jkmol-1 so you would expect the theoretical value of benzene to be -120 x 3=-360 however it is actually lower at -208 this means Bezene is more stable than expected

Enthalpy change of hydration is less exothermic than expected

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5
Q

what is the delocalisation energy of benzene

A

delocalisation energy of benzene-difference between the two values of enthalpy change of hydrogenation

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6
Q

describe the evidence used to refute Kekules model of benzene
(c-c bond length)

A

its is between (1.40) the lenght of a single bond (1.55) and a double bond (1.34)
ALL C-C BONDS IN BENZENE ARE THE SAME LENGTH

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7
Q

draw the delocalised pi bond model of benzene

A

in booklet
-1X delocalised pi bond
-6 electrons are shared over 6C atoms

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8
Q

draw the kekule model of benzene

A

in booklet
-3X localised pi bond two
-2 electrons are shared between two carbon atoms

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9
Q

describe the similarities between the Kekule model and benzene

A

both have a sideways overlap of P-orbitals above and below the plane of the molecule

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10
Q
A
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11
Q

Hoe to get from Benzene to nitrobenzene

A

-refluxed on a water bath at 60 degrees celcius (want)
-Add conc HNO3 and conc H2SO4

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12
Q

what is the reagent from benzene to nitrobenzene

A

conc HNO3

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13
Q

what is the catalyst for benzene to nitrobenzene

A

conc H2SO4

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14
Q

write out the overall equation from benzene to nitrobenzene

A

in booklet

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15
Q

how do you get a polysubstitued benzene ring

A

if temperatures rise above 95
however you also have 2HNO3 and 2H2O

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16
Q

how is the nitronium ions produced

A

2H2SO4 + HNO3 ———-> NO2+ + H3O+ + 2HSO4-

17
Q

draw the electrophillic attack on the benzene ring

A

in booklet

18
Q

what is the equation of the regeneration of the catalyst

A

H+ + HSO4- -> H2SO4

19
Q

write the overall equation for the halogenation of benzene

A

in booklet

20
Q

what is the catalyst for the halogenation of benzene if the halogen reaction is
eg-cl2, br2

A

Alcl2
Febr2
-these are the halogen carriers

21
Q

how is the electrophile formed equation

A

Cl2 + AlCl3 -> AlCl4- + CL+

br2 + FeBr3 -> Febr4- + Br+

22
Q

draw the equation for the electrophilic attack on the benzene ring

A

in booklet

23
Q

write the equation for the regeneration of the catalyst

A

H+ +Alcl4- -> Alcl3 + HCl

24
Q

when reacting benzene with a haloalkane would you need a halogen carrier

A

yes
eg- FeBr3, AlCl3

25
Q

complete the reaction of chloropropane with benzene

A

in booklet

26
Q

complete the mechanism for propanoyl chloride with benzene

A

in booklet

27
Q

draw a phenol group

A

benzene ring with an OH group

28
Q

what do phenols react with to form salts

A

as phenol is a weak acid it can react with a string base EG-NaOH to form salt

29
Q

what cant phenols react with

A

weak bases eg-NaCO3

30
Q

why do electrophilic substation reaction occur more readily with Phenol then benzene

A

the lone pair of electrons on the O atom is partially delocalised into the delocalised pi system
this increase the electron density of the pi system in phenol so its more able to induce a dipole into the electrophille and is more suceptible to electrophillic attack

31
Q

what are the conditions you need when phenol react with bromine

A

room temperature and no catalyst

32
Q

what are the two observations you can produce when phenol reacts with bromine

A

-white precipitate of your produce
-orange to colourless

33
Q

what is the equation for phenol reacting with bromine

A

in booklet
-get 3Br and 3HBr

34
Q

what type of nitric acid does phenol react with

A

reacts with dilute nitric acid

35
Q

what are the conditions for phenol reacting with dilute nitric acid

A

room temperature
no calalyst

36
Q

describe the OH and NH2 group

A

-it is an electron donating group (donates 2 electrons to pi system)
-activates the 2,4 positions of benzene
-so reacts more readily

37
Q

describe the NO2 group

A

-it is an electron withdrawing group (withdraws 2 electrons from the pi system)
-activates the 3 position of benzene
-so reacts less readily

38
Q
A
39
Q
A

Year 2 chemistry (18 decks)

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