Alkenes

Question 1

What is a sigma bond

Answer 1

Direct overlap of orbitals

Question 2

What is a pi bond

Answer 2

Sideways overlap of adjacent p-orbitals

Question 3

Define stereoisomers

Answer 3

Molecules with the same structural formula but with a different arrangement of atoms in space

Question 4

What do E/Z isomerism must have

Answer 4

. C=C that cannot rotate
. Each C of the C=C has two different groups attached

Question 5

How do you find out which one is the higher priority

Answer 5

The atoms with the highest Mr is the higher priority

Question 6

What is a z isomer

Answer 6

If the high priority groups are both above or below the C=C

Question 7

What is an E isomer

Answer 7

If the high priority groups are on opposite sides

Question 8

What do cis-trans isomers must have

Answer 8

2 of the substituent groups are the same

Question 9

Why are alkenes more reactive then alkanes

Answer 9

Due the relatively low bond enthalpy of the pi bond

Question 10

What are the reagents, conditions, mechanism and product of the reaction hydrogenation

Answer 10

Reagents- alkene+ hydrogen(H2)
Conditions- Nickel catalyst, 150c
Mechanism- Addition
Product- Alkane

Question 11

What are the reagents, conditions, mechanism and the product of the reaction bromination

Answer 11

Reagents- alkene+ bromine
Conditions- Room temp( dropwise and shake)
Mechanism- Electrophilic addition
Product- dihaloalkane

Question 12

What are the reagents, conditions, mechanism and product of the reaction adding hydrogen halides

Answer 12

reagents- alkene+ hydrogen halide(HBr)
conditions- room temp
mechanism- electrophilic addition
Product- haloalkane

Question 13

What are the reagents, conditions, mechanism and product of the reaction hydration

Answer 13

reagents- alkene+ steam
conditions- concentrated H3PO4 and high temperature and high pressure
Mechanism- Electrophilic addition
Product- alcohol

Question 14

What do curly arrows represent

Answer 14

The movement of a pair of electrons

Question 15

Define an electrophile

Answer 15

A species that accepts a pair of electrons

Question 16

Define addition

Answer 16

2 species join together to form 1

Question 17

What is the order of the most stable to least stable carbocation

Answer 17

Most- Tertiary
- Secondary
Least-Primary

Question 18

How do you know which product will be the major product formed

Answer 18

The major product is formed from the most stable carbocation

Question 19

Define addition polymer

Answer 19

Are made when many unsaturated monomers join together and the pi bond breaks

Question 20

How are polymers unreactive

Answer 20

C-C and C-H bonds have a high bond enthalpy
Non-Polar

Question 21

What are the three main ways of disposal the polymers

Answer 21

1) Recycling
2) Combustion
3) Organic feedstock

Question 22

Describe the process of recycling polymers

Answer 22

1) Sorting- this is essential as recycling a mixture of different polymers renders the product unusable
2) Reclamation- the separated polymers are chopped into flakes, melted. The product is then used to make new products

Question 23

Describe the process of combustion of polymers

Answer 23

• Used to provide energy but need to remove toxic gas( when halogenated plastics are burnt, releasing HCl)
• Toxic gas can be removed by reacting with an alkali

Question 24

Describe the process of organic feedstock of polymers

Answer 24

• turned in to more useful organic compounds