aromatic compounds

Question 1

main type of reaction benzene undergoes

Answer 1

electrophilic substitution

Question 2

why is benzene less reactive then a phenol

Answer 2

• in phenol, lone pair of electrons from O of -OH are donated to the π system of the ring
• increasing electron density
• meaning electrophiles are attracted more easily

Question 3

evidence for delocalised model of benzene (3)

Answer 3

• does not react like an alkene - much less reactive - doesn’t decolourise bromine water (alkene does)
• the c-c bond length is between double and single
• the hydration enthalpy is not as expected (less energy produced when hydrated)

Question 4

are phenols acidic?

Answer 4

yes

Question 5

explain solubility of phenols

Answer 5

less soluble in water than an alcohol because of non-polar benzene ring - does partially dissolve

Question 6

reactions of phenol and:

• strong base
• weak base

Answer 6

• yes - (alcohol wouldn’t)

- no

Question 7

observations of reaction of bromine water by phenol (name products formed)

Answer 7

• decolourises bromine water

- white ppt. - 2,4,6-tribromophenol

Question 8

where does -NH2 direct to

Answer 8

2,4

Question 9

where does -OH direct to

Answer 9

2,4

Question 10

where does -NO2 direct to

Answer 10

3

Question 11

conditions required for nitration of phenol

Answer 11

• no conc. H2SO4 needed

- only dilute HNO3

Question 12

alkylation

Answer 12

adding a haloalkane to benzene, lengthening carbon chain by adding alkyl group - by reacting w. a chloroalkane

Question 13

special thing about alkylation

Answer 13

lengthens carbon chain

Question 14

acylation

Answer 14

adding an acyl group to benzene, forming a ketone

Question 15

-NO2 is: deactivating/activating?

Answer 15

deactivating

Question 16

-NH3 is: deactivating/activating?

Answer 16

activating

Question 17

what does activating mean?

Answer 17

the aromatic ring reacts more readily with electrophiles

Question 18

explain ease with which benzoic acid attracts electrophile

Answer 18

• COOH is electron withdrawing group

- hard to attract electrophile