Aromatic compounds

Question 1

Examples of electron donating groups

Answer 1

NH2

OH

Question 2

examples of electron withdrawing groups

Answer 2

NO2

COOH

Question 3

Electron donating

Answer 3

Prosthetic groups which donate electrons
increasing electron density at 2,4 and 6
electrophiles more likely to attack at 2,4 and 6

Question 4

Electron withdrawing

Answer 4

electronegative groups
withdraw/decrease electron density from 2,4 and 6
electrophiles more likely to attack 3 and 5

Question 5

What occurs at substituted benzene rings

Answer 5

electron density in the ring is distorted also distorting reactivity of C atoms

Question 6

conditions for nitration of benzene

Answer 6

conc HNO3

H2SO4

Question 7

conditions for nitration of phenols

Answer 7

dilute HNO3

Question 8

What are phenols

Answer 8

weak acids where OH group is directly attached to benzen ring

Question 9

Why are phenols more reactive than benze

Answer 9

Overlap of orbitals
electrons in p orbital of oxygen are partially delicacies into pi system
increasing electron density so more susceptible to attack from electrophile

Question 10

phenol + alkali

Answer 10

salt and water

Question 11

electrophile equation for nitration of benzene

Answer 11

HNO3 + H2SO4 -> NO2+ + HSO4- + H2O

Question 12

conditions for nitration of benzene

Answer 12

below 55C

to ensure single titration

Question 13

what occurs at the bromination of phenol

Answer 13

becomes de colourised

bromine reacts with phenol

Question 14

evidence for structure of benzene

Answer 14

Bonds all same length - due to delocalised electrons, higher electron density
Higher stability than theoretical model - enthalpy change of hydration is lower than theoretical
higher stability due to delocalised electrons

Question 15

identifying benzene

Answer 15

add bromine water
stays orange/brown
does not undergo bromination

Question 16

define arenes

Answer 16

molecules which contain a benzene ring

Question 17

Explain the relative resistance to bromination of benzene compared to phenol and cyclohexene

Answer 17

Benzene has delocalised electrons 
So has lower electron density 
Cannot polarise Br2 
Phenol, lone pair on oxygen are partially delocalised into the ring 
Cyclohexene has localised electrons