Alkenes And Polymers

Question 1

What 2 types of bonds make the C=C double bond?

Answer 1

Sigma and pi bonds

Question 2

How are pi bonds formed?

Answer 2

2 p-orbitals overlap, forming second bond. It fixes the C atoms into place, at either end of double bonds -> this prevents any rotation on bond

Question 3

Describe the structure of an alkene

Answer 3

Trigonal planar arrangement
Bond angle of 120*
3 electron density areas surround each carbon
Electron pairs repel as far out to minimise repulsions

Question 4

Which are more reactive, alkanes or alkenes?

Answer 4

Alkenes

Question 5

What reaction mechanism does an alkene undergo?

Answer 5

Electrophyllic addition

Question 6

What is an electrophile?

Answer 6

Electrophile is an electron pair acceptor

Question 7

What type of bond fission is required for an electrophyllic addition?

Answer 7

Heterolytic fission

Question 8

What is heterolytic fission?

Answer 8

Heterolytic fission is the breaking of a covalent bond with both of the bonded electrons going to one of the atoms, forming a cation (+ve) and an anion (-ve)

Question 9

Give an example of an industrial use of alkenes and explain how it is manufactured

Answer 9

Margarine
The manufacture of margarine:
Made from veg oil (liquids containing long hydrocarbon chains, C=C double bonds and polyunsaturated)
The oil must be hardened so it doesn’t soak.
Hydrogenation -> adds H molecules across double bonds in an addition reaction.
-> alters individual molecules
-> partially solidifies and hardens

Question 10

What is a polymer?

Answer 10

A polymer is a long molecular chain built up from monomer units

Question 11

What is a monomer?

Answer 11

A monomer is small molecules combine with many other monomers to form a polymer

Question 12

What are addition polymers?

Answer 12

Addition polymer is a very long molecular chain, formed by repeated addition reactions of monomers

Question 13

What is a repeat unit?

Answer 13

Specific arrangements of atoms that occurs in structure over and over again

Question 14

What are the 2 industrial processes to produce polymers?

Answer 14

Radical polymerisation

The Ziegler-natha process

Question 15

Give examples for the different uses of polymers

Answer 15

Polystyrene -> foam, packaging

Polypropylene -> containers, lab equipment (highly resistant to chemical attacks)

Polyethene -> grocery bags, bottles

Question 16

What is biodegradable material?

Answer 16

Material that is broken down naturally in the environment by living organisms

Question 17

What is an alkene?

Answer 17

Unsaturated hydrocarbons with the general formula CnH2n