4.1

Question 1

what are aliphatic hydrocarbons?

Answer 1

when carbon atoms are joined together in either a straight or branched chain.

Question 2

Alicyclic hydrocarbons

Answer 2

when the carbon atoms are joined together in a ring structure but are not aromatic

Question 3

aromatic hydrocarbons

Answer 3

when there is at least one benzene ring in the structure

Question 4

what is a homologous series

Answer 4

a series of organic compounds having the same functional group but with each successive member differing by ch2

Question 5

what is an Isomer?

Answer 5

organic compounds with the same molecular formula but different arrangements if atoms

Question 6

Alkanes general formula and facts

Answer 6

General formula- Cn H2n+2

Alkanes are saturated

cyclohexane has two fewer hydrogens.

Question 7

Trend in boiling point from small to large alkanes

Answer 7

the bigger the alkane, the higher the bp is.

This is due to the longer chains having a stronger induced dipole attraction due to more electrons and surface area.

Takes more energy to overcome

Question 8

Why do branched chains have lower boiling points?

Answer 8

They can’t pack as closely together and have small molecular surface areas so the induced dipole interactions are reduced.

Question 9

What is the issue with carbon monoxide?

Answer 9

The carbon monoxide binds to the haemoglobin before the oxygen can meaning less oxygen can be carried around your body leading to oxygen deprivation

Question 10

What is Heterolytic fission?

Answer 10

Where the bond breaks unevenly with one of the bonded atoms receiving both electrons from a bonded pair.

Question 11

What is homolytic fission?

Answer 11

When the bond breaks evenly and each receives one electron from the bonded pair two radicals are formed.

Question 12

What is a free radical?

Answer 12

A particle that has an unpaired electron and therefore very reactive.

Question 13

Free radical substitution.

Answer 13

• Can happen with bromine or chlorine
• Initiation: sunlight(uv) breaks the Cl2 bond to form two free radicals (photodissociation)
• Propagation: free radicals are used up and created in a chain reaction.
• Termination: free radicals react together to form a stable molecule.

Question 14

The issue with free radical substitution.

Answer 14

You don’t always get a particular product but a mixture of them.

Question 15

Alkenes general formula and facts.

Answer 15

the General formula is An H2n

They are all hydrocarbons and are unsaturated.

Question 16

What is a double bond made up of?

Answer 16

• A Sigma Bond is formed when two s orbitals overlap

* A pi bond is formed by the sideways overlap of two adjacent p orbitals

Question 17

Why are Alkenes more reactive than Alkanes

Answer 17

• Alkanes only contain C-C bonds and C-H bonds which are hard to break due to high bond enthalpy and also non polar
• Alkenes have a double bond and as the pi bond sticks out it’s more likely to be attacked by electrophiles. also a low bond enthalpy in the pi bond.

Question 18

What are Stereoisomers?

Answer 18

These have the same structural formula but a different arrangement in space.
This can occur due to lack of rotation about the double bond and cause E/Z isomerism

Question 19

What do the Cahn-Ingold-Prelog rules say?

Answer 19

The atom with the higher atomic number on each carbon is given priority (in E/Z isomerism)

Question 20

Electrophilic Addition reactions and why they happen.

Answer 20

• Happen to Alkenes
• the double bonds open up and atoms are added to the carbon atoms

*The double bond has lots of electrons so can be attacked by electrophiles.

Question 21

What is an electrophile?

Answer 21

Electron pair acceptors.

Question 22

Turning Ethene to Ethane

Answer 22

Reacts with hydrogen gas with a nickel catalyst and 150°c

Question 23

How to test for double bonds

Answer 23

Bromine water goes from orange to colourless.

As bromine is added across the double bond to form colourless dibromoalkane

Question 24

How to make Alcohols with Alkenes.

Answer 24

Hydrate with steam
300°c and a pressure of 60-70atm
conc Phosphoric(v) acid catalyst

Low yield but you can recycle unused alkenes

Question 25

Markownikoff’s rule

Answer 25

The major product from an addition of a hydrogen halide to an unsymmetrical alkene us the one where hydrogen adds to the carbon with the most hydrogens already attached.

Question 26

What’s a haloalkane?

Answer 26

An alkane with one or more halogen attached

Question 27

How to Alkenes form Polymers?

Answer 27

The double bonds in alkenes open up and join together to create polymers.

Question 28

Good and bad things about Polymers.

Answer 28

• They are unreactive so food doesn’t react with the coating on pans, plastic windows don’t rot.
• The lack of reactivity means they don’t degrade easily.

Question 29

How are waste plastics dealt with.

Answer 29

• Buried- generally used when the plastic is hard to separate, in small quantities and too hard to recycle.
• Reused- some can be melted and remoulded, others can be cracked into monomers and these can be used to make more plastics or other chemicals.
• Burnt- the heat can generate electricity, the Polymers can cause toxic gases when burnt and waste gases from the combustion are passed through scrubbers which can neutralise gases like hcl

Question 30

Biodegradable Polymers.

Answer 30

• They decompose quickly as organisms can digest them. They are made from renewable raw materials like starch.
• They still need to right conditions
• Scientists are also looking at photodegradable Polymers which decompose when exposed to sunlight.