Organic 2 Alkenes

Question 1

Bromine water test for C=C type and mechanism
Ratio

Answer 1

Electrophilic
Addition
One mole of alkene requires one mole of Br2 to saturate it

Question 2

Acidified potassium manganate (7) test

Answer 2

Purple decolourises
Redox (manganate reduced and organic molecule oxidised)
Produces a diol

Question 3

Alkene ➡️halogenoalkane
Reagent and conditions
Type and mechanism of reaction

Answer 3

Hydrogen halide
Electrophilic addition

Question 4

Mechanism for alkene➡️haloalkane

Answer 4

Permanent dipole on HX
Curly arrow from C=C to delta + H (electrophile)
HX bond breaks by heterolytic fission
Carbocation intermediate formed
Curly arrow from - X with lone pair to the C+
Haloalkane formed
HX:C=C
1 : 1

Question 5

Alkenes➡️dihaloalkanes
Reagent
Type and mechanism of reaction

Answer 5

Halogen
Electrophilic addition

Question 6

Mechanism for alkene➡️dihaloalkane

Answer 6

Dipole on X-X because as it comes close to the alkene, a dipole is induced as electrons are repelled by the C=C
Curly arrow from C=C to delta positive X
Heterolytic fission of X-X bond
Carbocation intermediate
Curly arrow from -X with lone pair to C+
Dihaloalkane formed
X2. : C=C
1. : 1

Question 7

Markovnikovs rule

Answer 7

Major product is more stable than the minor product
Carbocations with more alkyl groups are more stable because they feed electrons towards the positive charge
Tertiary carbocations therefore have greater electron inducing effect

Question 8

Hydration of alkenes
Product
Conditions
Reagent
Type and mechanism of reaction

Answer 8

Alcohol
Steam
Concentrated phosphoric acid catalyst (H3PO4)
Addition

Question 9

Markovnikovs rule reactions

Answer 9

Alkene+ hydrogen halide
Alkene+ steam

Question 10

Alkene➡️diol
Reagent
Type and mechanism

Answer 10

Acidified potassium manganate
Addition reaction
Oxidises double bond

Question 11

Polymers

Answer 11

Unreactive because they’re saturated molecules
100% atom economy
Intermolecular forces and therefore their physical properties vary depending on their side groups

Question 12

Recycling polymers

Answer 12

Thermosetting- chipped to be reformed into new products
Thermosoftening- remoulding them into new products by melting

Question 13

How to remove toxic gases due to incineration

Answer 13

Neutralisation

Question 14

Feedstock

Answer 14

Some plastics can be cracked into monomers which can be used as organic feedstock to make more plastics or other chemicals
Fuels

Question 15

Sustainability of polymers

Answer 15

• use environmentally friendly reactant molecules
• use renewable raw materials
• minimise waste
• use catalysts to keep energy use to minimum
• ensure lifespan of polymer appropriate for its use

Question 16

making margarine by catalytic hydrogenation of unsaturated vegetable oils

Answer 16

Unsaturated long hydrocarbon chains in veg oils
Converted to saturated ones
Raises melting temperature of the oil so that it solidifies at room temperature

Question 17

Alkene➡️alkane

Answer 17

Add hydrogen
Nickel catalyst or platinum
Addition