Alkenes

Question 1

What are alkenes?

Answer 1

Unsaturated hydrocarbons C=C bond

Question 2

What is the general formula of alkenes?

Answer 2

CnH2n

Question 3

How is a pi bond formed?

Answer 3

When electrons in the adjacent p orbital overlaps

Question 4

What bond restrict the rotation of carbon atoms?

Answer 4

Pi bond

Question 5

What is the angle and shape of a double bond?

Answer 5

Trigonal planar 120 degrees

Question 6

Are alkenes more or less reactive than alkanes?

Answer 6

More reactive due to high electron density of double bond and pi bond is easier to break

Question 7

What intermolecular forces of attraction do alkenes have?

Answer 7

London forces due to it not being polar

Question 8

What is an electrophile?

Answer 8

Electron pair acceptors

Question 9

What is the most stable carbocation intermediate?

Answer 9

A tertiary carbocation because it has the most alkyl groups attached, the most stable carbocation

Question 10

Major products will be formed from which kind of carbocation?

Answer 10

Secondary or teriary

Question 11

What conditions are needed for the electrophilic addition of H2O to an alkene?

Answer 11

Hydration reaction uses steam in the presence of an acid catalyst

Question 12

What conditions are needed for the electrophilic addition of a hydrogen halide to an alkene?

Answer 12

Room temperature

Question 13

Draw a mechanism for the reaction of HBr and ethene

Answer 13

…

Question 14

How can an alkene be converted into an alkane?

Answer 14

• Alkene + Hydrogen = Alkane

- Hydrogenation, nickel catalyst 150 degrees

Question 15

How do stereoisomerism arise?

Answer 15

The double bonds causes restriction and the groups attached to each carbon atom are therefore fixed.

Question 16

What is the difference between cis-trans isomerism and E/Z isomerism?

Answer 16

For cis-trans one of the groups attached on each carbon atom of the double bond must be the same and for E/Z one of the groups attached on each carbon atom of the double bond must be different

Question 17

What does E and Z stand for in stereoisomerism?

Answer 17

E = opposite side
Z = the same side

Question 18

What was Markownikoff’s rule?

Answer 18

The product with the most alkyl groups attached to it will be the major product (secondary or tertiary) and the product with the least alkyl groups attached will be the minor product (primary)

Question 19

What carbocation is the most stable and why?

Answer 19

Tertiary carbocations has the most alkyl groups which means the positive charge of the carbocation is the most spread out, this makes the ion more stable.

Question 20

What is an addition polymer?

Answer 20

Many monomers bonded together via rearrangement of bonds

Question 21

What are monomers?

Answer 21

Single units that combine to form polymers. Usually have a C=C bond which breaks to leave a repeating unit.

Question 22

What are the ways in which plastics can be disposed?

Answer 22

• Landfill
• Combustion
• Reuse/recycle
• Electricity generation
• Organic feedstock

Question 23

What are the disadvantages of recycling?

Answer 23

• Plastics must be sorted
• Expensive
• Labour intensive
• Requires high technology

Question 24

Why is PVC hazardous?

Answer 24

Due to its high chlorine content and when burnt it releases hydrogen chloride

Question 25

Explain what happens in organic feedstock?

Answer 25

Plastics are separated and broken down into small organic molecules and then used to produce plastics

Question 26

How does photodegradable polymers break down?

Answer 26

Polymers are weakened by absorbing light to start the degradation

Question 27

How does biodegradable polymers break down?

Answer 27

Broken down by microorganisms into water, carbon dioxide and biological compounds