aromatic chemistry

Question 1

describe the bonding in the kekule structure of benzene

Answer 1

localised, alternating pi bonds formed from the sideways overlap of p orbitals forming 3 pi bonds

Question 2

describe the bonding in the delocalised model of benzene

Answer 2

all six pairs of p orbitals overlap to form a delocalised ring structure

Question 3

how would you expect benzene to react based on the kekule model

Answer 3

reactive and decolourise bromine

Question 4

what was actually found about the reactivity of benzene

Answer 4

unreactive and requires a halogen carrier catalyst

Question 5

what would you expect the bond lengths to be in benzene based on the kekule structure

Answer 5

alternating forming an irregular hexagon based on that C- C bond lengths are greater than C=C

Question 6

what was actually found in terms of bond lengths in benzene

Answer 6

all the same length forming a regular hexagon intermediate of that of C-C and C=C

Question 7

what would you expect the enthalpy of hydrogenation of benzene to be based on the kekule structure

Answer 7

3x that of cyclohexene due to having 3 C=C bonds

Question 8

what was actually found regarding the enthalpy of hydrogenation of benzene

Answer 8

less exothermic than expected as it is more stable

Question 9

what type of reaction is the nitration of benzene

Answer 9

electrophilic substitution

Question 10

what is the functional group change in the nitration of benzene

Answer 10

benzene - nitrobenzene

Question 11

what are the conditions and reagents for the nitration of benzene

Answer 11

conc HNO3 and conc H2SO4 catalyst

Question 12

write the equation for the formation of nitrobenzene from benzene

Answer 12

benzene + HNO3 -> nitrobenzene + H2O

Question 13

what is the electrophile in the nitration of benzene

Answer 13

NO2+

Question 14

what type of reaction is the halogenation of benzene

Answer 14

electrophilic substitution

Question 15

what are the conditions and reagents for the bromination of benzene

Answer 15

AlBr3 + Br2

Question 16

what is the electrophile in the bromination of benzene

Answer 16

Br+

Question 17

what type of reactions are alkylation and acylation of benzene

Answer 17

friedel crafts electrophilic substitution

Question 18

why are friedel crafts reactions important in organic synthesis

Answer 18

formation of C-C bond by extending the carbon chain

Question 19

what are the conditions and reagents for alkylation of benzene

Answer 19

AlCl3 and a chloroalkane

Question 20

what is the electrophile in the alkylation of benzene forming ethylbenzene

Answer 20

CH3CH2+

Question 21

what are the conditions and reagents for acylation of benzene

Answer 21

AlCl3 and an acyl chloride

Question 22

what does acylation of benzene form

Answer 22

phenyl ketone

Question 23

why are alkenes more reactive than benzene

Answer 23

benzene has a delocalised pi ring whereas alkenes have localised electrons, this gives them more electron density making them more susceptible to electrophilic attack

Question 24

what is a phenol

Answer 24

a weak acid where a hydroxyl group is directly bonded to a benzene ring

Question 25

as phenol is a weak acid, what does it react with

Answer 25

metals and metal hydroxides but NOT carbonates

Question 26

what is the name of the salt formed when phenol reacts with sodium hydroxide

Answer 26

sodium phenoxide

Question 27

why is phenol more reactive than benzene

Answer 27

the oxygen lone pair from the hydroxyl group partially delocalises into the pi ring which increases electron density making it more susceptible to electrophilic attack

Question 28

how can you see phenol is more reactive than benzene through its halogenation reactions

Answer 28

no halogen carrier catalyst required

Question 29

how can you tell phenol is more reactive than benzene through its nitration reactions

Answer 29

reacts with dilute HNO3 and no H2SO4 catalyst needed

Question 30

what is the product formed from the bromination of phenol

Answer 30

2,4,6-tribromophenol

Question 31

write the overall equation for the bromination of phenol

Answer 31

phenol + 3Br2 -> 2,4,6-tribromophenol + 3HBr

Question 32

what are the products for the nitration of phenol

Answer 32

2-nitrophenol and 4-nitrophenol

Question 33

why does the nitration of phenol produce a mixture of products

Answer 33

due to the directing effect

Question 34

what are electron donating groups

Answer 34

-OH and -NH2

Question 35

what are electron withdrawing groups

Answer 35

-NO2