Reactions Of Alkenes

Question 1

Hydrogenate

Answer 1

Add hydrogen across C=C bond
Nickel catalyst
High temperatures

Question 2

Combust

Answer 2

Adds oxygen
Smoky flame
Makes CO2 and H2O

Question 3

Hydration

Answer 3

Add steam
Use H3PO4 (phosphoric acid)
Makes alcohol (H2O splits into H and OH; each adds on to either side of the double bond)

Question 4

Hydrogen Compounds [H-X]

Answer 4

H and X add across C=C bond
Electrophilic addition

Question 5

Alkene + acidified potassium manganate (K2MnO4)

Answer 5

Needs H+ ions (acidified potassium manganate)
Purple -> colourless
Makes diol

Question 6

Halogenation (simple)

Answer 6

Makes dihalogenoalkane
Adds halogen across C=C bond
Electrophilic addition
Bromine makes it turn colourless

Question 7

Halogenation (bromine water)

Answer 7

Tests for alkenes- brown/orange to colourless
Make halogenoalcohol (from the water)

Question 8

Hydrogen halides

Answer 8

Electrophilic addition
Needs positive or partially positive charge