Chapter 13

Question 1

What are orbitals?

Answer 1

Regions around the nucleus which can hold up to 2 electrons

Question 2

What are sigma bonds?

Answer 2

Head-on overlap of 2 orbitals. It is positioned on a line directly between 2 bonding atoms and are single bonds.

Question 3

What are Pi bonds?

Answer 3

Pi bonds are formed by the sideway overlap of 2 p orbitals. It results in a high electron density above and below the sigma bond. It locks the 2 atoms in position and prevents rotation around the double bond.

Question 4

Characteristics of Alkenes

Answer 4

General formula is CnH2n
It is aliphatic with 1 double bond
120°
Trigonal planar 
Has sigma and pi bonds

Question 5

Pi bonds vs Sigma bonds

Answer 5

Pi bonds:
Overlap of p orbitals 
2nd bond in a double bond
Above and below the plane of Carbon atoms 
Sigma bonds:
Overlap of any orbitals 
Single bonds
On the plane of Carbon atoms

Question 6

What are stereoisomers?

Answer 6

Stereoisomers have the same structural and molecular formula but have a different arrangement of atoms in space. There are 2 types:
E/Z isomers
Optical isomerism

Question 7

What is E/Z isomerism?

Answer 7

It occurs due to the rigidity of the C=C bond
The pi bond above and below the carbon atoms restrict the carbons from being able to rotate
The 2 conditions needed for E/Z isomerism to occur are a C=C bond and different groups attached to each carbon in the double bond

Question 8

What is Cis/Trans isomerism?

Answer 8

Cis/trans isomerism is a special kind of E/Z isomerism where 1 group of the groups attached to each carbon has to be a hydrogen

Question 9

Reactivity of alkenes

Answer 9

Alkenes are more reactive than alkanes due to the presence of a pi bond. Pi bonds are easier to break down

Question 10

Addition reactions of alkenes

Answer 10

Hydrogen in presence of a nickel catalyst
Halogens
Hydrogen halides
Steam in the presence of an acid catalyst

Question 11

Hydrogenation

Answer 11

It produces an alkane

The hydrogen is added across the double bonds

Question 12

Halogenation

Answer 12

Alkenes undergo a rapid addition reaction with the chlorine, bromine and iodine
It can be used to test for a double bond as the colour of the halogen becomes colourless
Produces haloalkanes

Question 13

Addition reactions of alkenes with hydrogen halides

Answer 13

Reacts with gaseous hydrogen halides at room temperature to form haloalkanes
Forms haloalkanes
There can be 2 products

Question 14

Hydration reaction of alkenes

Answer 14

Alcohols are formed
Alkenes react with steam
Steam adds across the double bond
Can form 2 possible products

Question 15

What is an electrophile?

Answer 15

An electrophile is an atom or group of atoms that are attracted to electron-rich centres and can accept an electron pair. It is usually a positive ion or molecule containing a partial positive charge.

Question 16

What is a nucleophile?

Answer 16

A nucleophile is a chemical species that donates an electron pair to form a chemical bond in relation to a reaction. All molecules or ions with a free pair of electrons or at least one pi bond can act as nucleophiles

Question 17

What is carbocation stability?

Answer 17

Each alkyl group will donate and push electrons towards the positive charge of the carbocation.
If there are more alkyl groups, the positive charge will be spread out more and therefore will make it more stable. The carbocation formed is more likely to be the more stable carbocation.

Question 18

What is Markownikoff’s rule?

Answer 18

When a hydrogen halide reacts with an unsymmetrical alkene, the hydrogen of the hydrogen halides attaches itself to the carbon atom of the alkenes with the greater number of hydrogen atoms.

Question 19

What is addition polymerisation?

Answer 19

Unsaturated alkene molecules produce long saturated chains containing no double bonds. Industrial polymerisation is carried out at high temperatures and high pressure using catalysts

Question 20

What is recycling?

Answer 20

Recycling polymers reduces their environmental impact by conserving finite fossil fuels and decreasing the amount of waste. Polymers are sorted then chopped into flakes, washed, dried then melted. Then it is cut into pellets and used by manufactures.

Question 21

What is PVC recycling?

Answer 21

Disposal and recycling of PVC is hazardous due to high chlorine content
Can be grounded up or use solvents to dissolve and recovered using precipitation

Question 22

What can waste polymers also be used as?

Answer 22

Waste polymers can be burned to produce heat, generating steam to generate electricity

Question 23

What is feedstock recycling?

Answer 23

Describes the chemical and thermal processes that can reclaim oil, monomers or gasses from waste polymers.
The products can be used as raw materials to produce new polymers.
Polymers can be unsorted and still be recycled

Question 24

What are biodegradable and photodegradable polymers?

Answer 24

Biodegradable polymers are broken down by microorganisms into water, carbon dioxide and biological compounds. They are made from starch or cellulose.
Photodegradable polymers are weakened by light instead