Alkenes_Reagents and conditions

Electrophilic addition of hydrogen halides

Reagents: HX (g)

Conditions: dry HX(g), room temp

Electrophilic addition of steam

Reagents: H2O(g)

Conditions: conc. H3PO4 catalyst

Electrophilic addition of halogens in CCl4

Reagents: X2 dissolved in an inert solvent (eg. CCl4 or CH2X2)

Conditions: dark, room temp

Electrophilic addition of halogens in H2O

Reagents: X2 in water 

Conditions: dark, room temp

Reduction of alkenes

Reagent: H2

Conditions: Ni/Pt/Pd catalyst

Combustion of alkenes

CnH2n + (3n /2) O2(g) → nCO2(g) + nH2O(l)

Oxidation with cold, alkaline KMnO4

Mild oxidation

Reagents: KMnO4 (aq), NaOH (aq)

Conditions: Cold

Observations:

• Purple KMnO4 decolourised

• Brown-black ppt of MnO2 observed

Oxidation with cold, acidified KMnO4

Mild oxidation

Reagents: KMnO4 (aq), H2SO4 (aq)

Conditions: Cold

Observations: Purple KMnO4 decolourised

Oxidation with hot, acidified KMnO4

Strong oxidation

Reagents: KMnO4(aq), H2SO4(aq)

Conditions: Heat/ heat under reflux

Observations:

• Purple KMnO4 decolourised

• For terminal alkenes, a colourless gas (CO2) which forms a white ppt with limewater is evolved

Oxidation with hot, alkaline KMnO4

Strong oxidation

Reagents: KMnO4 (aq), NaOH (aq)

Condition: Heat/ heat under reflux

Observations:

• Purple KMnO4 decolourised

• Brown-black ppt of MnO2 observed