Aromatic Chemistry Word Stimulants

Question 1

Benzene

Answer 1

C6H6

Question 2

Benzene naming

Answer 2

-benzene

phenyl-

Question 3

Kekule model

Answer 3

Alternating c=c , c-c

Question 4

Delocalised model
(and electrons involvement)

Answer 4

Planar, cyclic, hexagonal hydrocarbon
Each C has 4 e- available for bonding - 2 in sigma bond to C-C-C ; 1 in sigma bond to C-H
1 e- in p orbital (right angles to plane of C-H sigma bond)
Delocalised ring of electron density above and below ring

Question 5

Delocalised model evidence

Answer 5

Bond length
Enthalpy change of hydrogenation
Resistance to reaction

Question 6

Bond length (Delocalised model)

Answer 6

All C-C bonds same length - 0.139nm
C-C : 0.153 nm
C=C : 0.134 nm

Question 7

Enthalpy change of hydrogenation (Delocalised model)

Answer 7

Expected : 3 (C=C) x120 = -360
Actual : -208 kJ mol-1
Less exothermic than expected
More stable than kekule

Question 8

Resistance to reaction (Delocalised model)

Answer 8

Does not decolourise bromine (C=C should)

Less reactive than alkenes - no electrophilic addition

Question 9

Arenes

Answer 9

Undergo substitution reactions
Less reactive than alkenes (electrophilic substitution)
Low pi electron density
Only react with bromine in presence of halogen carrier

Question 10

Substitution reactions

Answer 10

H replaced by electrophile

Question 11

Alkenes

Answer 11

Electrophilic addition

high pi electron density - readily attacks and polarises halogens

Question 12

Nitration conditions

Answer 12

Benzene + conc HNO3
Conc H2SO4 (catalyst)
50c
NO2

Question 13

Electrophilic substitution steps

Answer 13

Formation of electrophile (accepts pair of e-)
Formation of organic product (immediate)
Catalyst regeneration

Question 14

Nitration steps/equations

Answer 14

C6H6 + HNO3 > C6H5NO2 + H2O
HNO3 + H2SO4 > NO2+ + HSO4- + H2O
C6H6 > C6H5NO2 + H+
H+ + HSO4- > H2SO4

Question 15

Halogenation conditions

Answer 15

Benzene + Halogen
Halogen carrier (eg AlCl3, FeCl3)
Room temp

Question 16

Halogenation steps/equations

Answer 16

C6H6 + Br2 > C6H5Br + HBr
Br2 + FeBr3 > Br+ + FeBr4-
C6H6 > C6H5Br + H+
H+ + FeBr4- > FeBr3 + HBr

Question 17

Alkylation

Answer 17

Halogen carrier + aromatic compound

Introduce alkyl group to benzene ring (H replaced by R)

Question 18

Acylation

Answer 18

Aromatic + acyl chloride > Aromatic ketone
Halogen carrier
H replaced by RCO

Question 19

Phenol

Answer 19

-OH bonded directly to aromatic ring

Question 20

Phenol Weak Acid

Answer 20

Weakly dissociates on H2O (> penoxide ion)
Turn pH paper acidic colour
More acidic than OH, less than COOH
Does not react with Na2CO3 - no gas bubbles
COOH + Na2CO3 > CO2

Question 21

Phenol neutralisation reaction

Answer 21

Phenol + NaOH > C6H5O-Na+ (salt) + H2O

Question 22

Phenol electrophilic subsitution

Answer 22

More reactive than benze
Milder conditions
No halogen carrier
Room temperature
Dilute HNO3

Question 23

Phenol + Bromine water

Answer 23

White ppt

Bromine discoloured

Question 24

Phenol more reactive than Benzene

Answer 24

More susceptible to electrophilic attack
OH - lone pair donated to pi system; electron density increases (attracts electrophiles more strongly - polarised)
No halogen carrier, room temp, dilute not conc
Trisubsituted product

Question 25

Distribution

Answer 25

Second substitution of monosubsituted benzene > multisubstitued product

Question 26

Electron donating groups

Answer 26

Eg phenol
OH electron donating
Increases electron density of benzene
Activates - reacts more readily with electrophiles

Question 27

Electron withdrawing groups

Answer 27

Eg Nitrobenzene
NO2 electron donating
Decreases electron density
Deactivates - reacts less readily with electrophiles

Question 28

Directing effects

Answer 28

Electron withdrawing : 3-directing

Electron donating : 2, 4-directing

Question 29

3-directing group

Answer 29

Electron withdrawing
NO2
COOH, CN, CHO

Question 30

2, 4-directing group

Answer 30

Electron donating
OH
NH2
-Cl, -Br, -R