Alkenes

Question 1

What is the general formula of an alkene

Answer 1

CnH2n

Question 2

what kind of isomerism does an alkene form

Answer 2

E/Z

Question 3

how is an alkene formed

Answer 3

Through cracking

Question 4

what are the uses of alkenes

Answer 4

plastics, etc

Question 5

how do we test for an alkene

Answer 5

bromine water

orange to colourless

Question 6

what are the two types of polymers

Answer 6

-natural and synthetic

Question 7

Why do EZ isomers form

Answer 7

because of restricted rotation

Question 8

Why are alkenes unsaturated?

Answer 8

they have a double bond

Question 9

why are alkenes reactive

Answer 9

double bonds have high electron density

Question 10

What kind of reaction do alkenes undergo

Answer 10

electrophilic addition

Question 11

What are electrophiles

Answer 11

Electron pair acceptor

Question 12

Give examples of electrophiles

Answer 12

H-BR, H2SO4, BR-BR

Question 13

How do we test for alkenes

Answer 13

add bromine water (example of electrophilic addition)

Positive test: orange to colourless

Question 14

Why is Br-Br polarised

Answer 14

when bromine molecule approaches an a double bond, electrons shift to the other side, because they repel, this makes an induced dipole

Question 15

How do we know what the major or minor product would be

Answer 15

• Depends on stability
• more alkyl groups bonded to carbocation the more stable the intermediate it
• alkyl groups push electrons towards positive carbocation making it more stable

Question 16

What alkenes produce multiple products

Answer 16

Unsymmetrical

Question 17

How can we make alcohol from alkyl hydrogen sulfates

Answer 17

add cold water to warm ethyl hydrogen sulfate will form ethanol
this is called hydrolysis

Question 18

What are the two types of polymers

Answer 18

Natural: proteins and rubber
Synthetic: poly(propene)

Question 19

Why can’t poly(alkenes) degrade

Answer 19

• Saturated molecules
• non polar which means they are unreactive
• which means it can’t be attacked by nucleophiles

Question 20

What are the properties of polyalkanes

Answer 20

• Strong intermolecular forces for long chains, because
• This makes them rigid and stronger

Shorter polymers

• have less van der waals, and have branches
• flexible
• weaker

Polyalkanes with halogens

• form stronger perement dipole dipole
• so they last longer

Question 21

What is the role of plasticers

Answer 21

• Make polymers more flexible
• they slide between the polymer chains pushing them apart, this weakens the van der waal forces between the chains, which makes them easier to slide over
• so this means the polymer is easier to bend
• PVC is used in pipes and stuff