phenol and directing groups

Question 1

Structure of phenol.

Answer 1

compound containing a hydroxyl (-OH) group

Question 1

How to determine whether a molecule is a phenol or an alcohol.

Answer 1

-OH must be directly bonded to the benzene ring to be a phenol. Otherwise, properties will be that of an alcohol.

Question 2

Evidence to prove that phenols are weak acids.

Answer 2

Will react with NaOH (Strong base).

Will NOT react with carbonates (weak base).

Question 3

How to test for the presence of a phenol in a compound.

Answer 3

1- add bromine water - white ppt

2- add iron 3 chloride turns purple

3- react with sodium carbonate–> no reaction

Reaction with strong bases (NaOH).

Question 4

Observations of bromination of phenol.

Answer 4

Bromine water is decolourised. White precipitate forms.

orange - white ppt

Question 5

Catalyst for phenol’s electrophilic substitution with bromine.

Answer 5

None

Question 6

Equation for bromination of phenol.

Answer 6

Question 7

Products of phenol’s bromination.

Answer 7

2,4,6-tribromophenol and 3HBr

Question 8

Catalyst for phenol’s nitration.

Answer 8

No catalyst required

Question 9

What shows that phenol is more reactive than bromine with its nitration reaction?

Answer 9

Dilute nitric acid not concentrated. No catalyst required.

Question 10

What must all acids be in benzene’s electrophilic substitutions?

Answer 10

Concentrated

Question 11

Reactant of benzene’s electrophilic substitution - nitration.

Answer 11

Concentrated nitric acid

Question 12

Products of phenol’s nitration.

Answer 12

Mix of 2-nitrophenol and 4-nitrophenol

Question 13

Equation of phenol’s nitration.

Answer 13

Question 14

What are the 2- and 4- directing groups?

Answer 14

-OH and -NH2

Question 15

What are the -3 directing groups?

Answer 15

-NO2

Question 16

What directing group is -NO2?

Answer 16

3-

Question 17

What directing group is -NH2?

Answer 17

2- and 4-

Question 18

What directing group of -OH?

Answer 18

2- and 4-

Question 19

Is benzene, unsaturated or saturated depending on the model (Kekule or delocalised)

Answer 19

For both, benzene is unsaturated

Question 20

name this

Answer 20

2- nitrophenol

Question 21

name this

Answer 21

2- hydroxylbenzoic acid

Question 22

name this

Answer 22

2- phenyl ethanol

Question 23

name this

Answer 23

4-ethyl phenol

Question 24

name this

Answer 24

3- phenyl propan-1-ol

Question 25

name this

Answer 25

4 - bromo - 2 chloro - nitro phenol

Question 26

name this

Answer 26

2,4,6- trichlorophenol

Question 27

what type of acids are phenols

Answer 27

weak acids (so easily loses H+)

Question 28

is phenol a weaker acid than carboxylic acid?

Answer 28

yes

Question 29

phenol vs alcohols vs carboxylic acids

Answer 29

Question 30

why can bromination of phenol occur/ why phenol more reactive than benzene

Answer 30

1- lone pair of electrons on oxygen atom is donated into delocalised pi system on benzene ring/ are delocalised into ring 2-increases electron density in ring 3- phenol able to attract electrophile 4- can polarise br2

Question 31

reagents and conditions for nitrification of benzene

Answer 31

conc h2so4 and conc hno3 50 degrees

Question 32

reagents and conditions for nitrification of phenol

Answer 32

dilute h2s04 and dilute hno3 room temp

Question 33

positions on the benzene ring

Answer 33

Question 34

2- and 4- directing meaning

Answer 34

electron donation - activating - more reactive ortho and para directing lone pair delocalised into ring

Question 35

3 directing meaning

Answer 35

electron withdrawing deactivating - less reactive meta directing electron density is withdrawn out of ring

Question 36

all the directing groups

Answer 36

Question 37

explain why phenol is nitrated more readily than benzene?

Answer 37

Phenol a lone pair of electrons on Oxygen is partially delcoalted into the Pi ring 2- electron density increases 3- phenol more susceptible to electrophilic attack 4- phenol polarises electrophile more

Question 38

separating organic molecules

Answer 38

liquid - distillation solid - recrystallisation

Question 39

How could you distinguish between a sample of phenol and carboxylic acid

Answer 39

react with sodium carbonate carboxylic acid - fizzes phenol- no reaction

Question 40

relative easy of ntitration of phenol, benzene and benzoic acid

Answer 40

phenol a (lone) pair of electrons on O is (partially) delocalised/donated into the π-system / ring ✓ Reactivity of benzoic acid The –COOH group on benzoic acid is an electron withdrawing group ✓ Links electron density in π-bond to reactivity In phenol electron density is higher AND The ring is more susceptible to attack OR In benzoic acid electron density is lower AND The ring is less susceptible to attack ✓

Question 41

(ii) Another student attempts the same synthesis but carries out reduction before bromination. The student was surprised to find that two structural isomers of 3-bromophenylamine had been formed instead of the desired organic product. Explain this result and suggest the structures of the two isomers that formed.

Answer 41

Nh2 Is 2,4 directing

Question 42

benzene N02 ---> NH2

Answer 42

redution sn/ con HCl to amine