Arenes Flashcards

1
Q

Physical properties of benzene

A

Structure: Trigonal planar, non-polar
1. low MP and BP
2. Soluble in organic solvents, insoluble in water
3. poor electrical conductivity
( electrons in benzene delocalises within benzene molecule. electrons need to delocalise across benzene molecules)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Explain the resonance stability of benzene

A
  • Each carbon atom is sp2 hybridised, hence each C atom has an unhybridised p orbital
  • The p orbital will all form a continuous sideway overlap
  • The pi electrons delocalise across all 6 C atoms
  • Delocalised pi electron cloud formed, making benzene very stable
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why does benzene undergo substitution and not addition?

A
  • Substitution preserves the stability of benzene
  • Addition disrupts the stability of benzene, which is energetically unfavourable
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Electrophilic substitution with NO2+ to form nitrobenzene

A
  • concentrated HNO3, concentrated H2SO4 catalyst, 55 degrees
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Electrophilic substitution with halogen

A

Cl2(g), anhydrous AlCl3/FeCl3(s), warm OR
Br2(g), anhydrous AlBr3/FeBr3(s), warm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Alkylation (Step-up reaction)

A

RX, anhydrous AlX3/FeX3, warm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q
A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Electrophilic substitution (Nitration) for methylbenzenes

A

concentrated HNO3, concentrated H2SO4 catalyst, 30 degrees

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Electrophilic Substitution (Halogenation) for methylbenzenes

A

Cl2(g), anhydrous AlCl3/FeCl3(s), room temperature OR
Br2(g), anhydrous AlBr3/FeBr3(s), room temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

FRS for methylbenzenes

A

Monosub: Limited Cl2/Br2, UV light
Multisub: Excess Cl2/Br2, UV light (remove all H in alkyl)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Side-chain oxidation for methylbenzenes

A

Acidic condition:
- KMnO4, dilute H2SO4, heat under reflux
Basic condition:
- KMnO4, dilute NaOH, heat under reflux
- methylbenzene: benzoic acid (white solid) + H2O
- for ethylbenzene and longer, benzoic acid (white solid) + CO2, H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why electrophilic substitution for methylbenzene requires milder conditions?

A
  • presence of e-donating alkyl group increases electron density of benzene ring
  • methyl benzene more susceptible to electrophilic attack than benzene and is more reactive
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

electron-donating groups are () groups
electron-withdrawing are () groups

A

electron-donating are (activating) groups
electron-withdrawing are (deactivating groups)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly