Arenes – benzene & alkylbenzenes
Reaction Reagent(s) Organic product(s) Other product(s) Conditions/Catalysts Observations/Notes
Electrophilic substitution
-steamy white fumes/gas
given off
-electrophile formed by:
X -anhydrous AlBr3/AlCl3 X2 + AlX3 → X+ + [AlX4]-
Chlorination/
Bromination
Cl2/Br2
⏣ HX cat.
-room temp.
-cat. restored by:
H+ + [AlX4]- → HX + AlX3
-w/ ⏣CH3 → X at
position 2/4
-w/ ⏣CH3 & excess X2 →
X at positions 2,4,6
-electrophile formed by:
HNO3 + 2H2SO4 → NO2+
-in conc. HNO3 + conc. + 2HSO4- + H3O-
Nitration HNO3 (& H2SO4) NO2 H2O H2SO4 mixture -cat. restored by:
⏣ -25–60oC
-refluxed
H+ + HSO4- → H2SO4
-excess nitration → NO2
at position 3/5
-at >60oC w/ ⏣CH3 →
NO2 at positions 2,4,6
-steamy white fumes
-electrophile formed by:
CH3Cl + AlCl3 → CH2+ +
alkylbenzenes [AlCl4]-
Friedel-Crafts chloroalkanes ( CH3 -AlCl3 cat. -cat. restored by:
alkylation (CH3Cl)
⏣ )
HCl -heated H+ + [AlCl4]- → HCl +
AlCl3
-further alkylation can
occur as reaction
proceeds
-w/ ⏣CH3 → alkyl at
position 2/4
, Electrophilic substitution -steamy white fumes
-electrophile formed by:
CH3COCl + AlCl3 →
aromatic ketones CH3C+O + [AlCl4]-
Friedel-Crafts acyl chlorides ( COCH3 HCl -AlCl3 cat. -cat. restored by:
acylation (CH3COCl)
⏣ )
-heated H+ + [AlCl4]- → HCl +
AlCl3
-w/ ⏣CH3 → ketone
group at position 2/4
-steamy white fumes
CH2X -UV light -decolourises
Free radical substitution Cl2/Br2
⏣ HCl -boiled -w/ excess X2 → all H
atoms on alkyl chain
replaced by X
COOH -alkyl side-chains of any
Oxidation (hot) KMnO4/OH- then dil.
HCl ⏣ H2O -heated
-refluxed
length oxidised to
benzoic acid
Hydrogenation H2 ⬡ -Ni/Pt cat.
-type of addition reaction
-w/ ⏣CH3 →
-heated cyclomethylbenzene
Phenols
Reaction Reagent(s) Organic product(s) Other product(s) Conditions/Catalysts Observations/Notes
OH- phenoxide salts
(NaOH) ( O-Na+ H2O -room temp. -salt prod. = soluble
Acid-base ⏣ )
sodium phenoxide
Na ( O-Na+ H2 -molten phenol used -vigourous
⏣ )
-bubbling
Reaction Reagent(s) Organic product(s) Other product(s) Conditions/Catalysts Observations/Notes
Electrophilic substitution
-steamy white fumes/gas
given off
-electrophile formed by:
X -anhydrous AlBr3/AlCl3 X2 + AlX3 → X+ + [AlX4]-
Chlorination/
Bromination
Cl2/Br2
⏣ HX cat.
-room temp.
-cat. restored by:
H+ + [AlX4]- → HX + AlX3
-w/ ⏣CH3 → X at
position 2/4
-w/ ⏣CH3 & excess X2 →
X at positions 2,4,6
-electrophile formed by:
HNO3 + 2H2SO4 → NO2+
-in conc. HNO3 + conc. + 2HSO4- + H3O-
Nitration HNO3 (& H2SO4) NO2 H2O H2SO4 mixture -cat. restored by:
⏣ -25–60oC
-refluxed
H+ + HSO4- → H2SO4
-excess nitration → NO2
at position 3/5
-at >60oC w/ ⏣CH3 →
NO2 at positions 2,4,6
-steamy white fumes
-electrophile formed by:
CH3Cl + AlCl3 → CH2+ +
alkylbenzenes [AlCl4]-
Friedel-Crafts chloroalkanes ( CH3 -AlCl3 cat. -cat. restored by:
alkylation (CH3Cl)
⏣ )
HCl -heated H+ + [AlCl4]- → HCl +
AlCl3
-further alkylation can
occur as reaction
proceeds
-w/ ⏣CH3 → alkyl at
position 2/4
, Electrophilic substitution -steamy white fumes
-electrophile formed by:
CH3COCl + AlCl3 →
aromatic ketones CH3C+O + [AlCl4]-
Friedel-Crafts acyl chlorides ( COCH3 HCl -AlCl3 cat. -cat. restored by:
acylation (CH3COCl)
⏣ )
-heated H+ + [AlCl4]- → HCl +
AlCl3
-w/ ⏣CH3 → ketone
group at position 2/4
-steamy white fumes
CH2X -UV light -decolourises
Free radical substitution Cl2/Br2
⏣ HCl -boiled -w/ excess X2 → all H
atoms on alkyl chain
replaced by X
COOH -alkyl side-chains of any
Oxidation (hot) KMnO4/OH- then dil.
HCl ⏣ H2O -heated
-refluxed
length oxidised to
benzoic acid
Hydrogenation H2 ⬡ -Ni/Pt cat.
-type of addition reaction
-w/ ⏣CH3 →
-heated cyclomethylbenzene
Phenols
Reaction Reagent(s) Organic product(s) Other product(s) Conditions/Catalysts Observations/Notes
OH- phenoxide salts
(NaOH) ( O-Na+ H2O -room temp. -salt prod. = soluble
Acid-base ⏣ )
sodium phenoxide
Na ( O-Na+ H2 -molten phenol used -vigourous
⏣ )
-bubbling
