Organic Chemistry A1

Question 1

What are polymers?

Answer 1

Large molecules made up of small repeating units.

Question 2

What is addition polymerisation?

Answer 2

When alkenes react together by breaking open their double bonds forming a long chain.

Question 3

How are polymers disposed of? What are the strengths and limitations of these?

Answer 3

LANDFILL
+ Cheap and easy
- Not biodegradable

COMBUSTION FOR ENERGY
+ Releases energy
- Makes CO2
- Makes dangerous gases

RECYCLING
+ Less material goes to landfill
+ Conserves finite fossil fuels
- Must be sorted and collected
- Some plastics are hard to recycle

FEEDSTOCK RECYCLING
+ Can handle unsorted and unwashed polymers
+ Can be used as raw material to make a new polymer
- Requires a high amount of energy

Question 4

Name 2 new polymers and describe them

Answer 4

BIOPLASTICS are produced from plants.
+ Renewable, sustainable, biodegradable, do not contains halogens so don’t produce toxic gases.

PHOTODEGRADABLE POLYMERS are weakened by light and then start to break down.

Question 5

How can HCl gas from burning PVC be removed from waste mixture?

Answer 5

Neutralise with a base - e.g. NaCO3

Question 6

Identify a hazard of burning PVC - poly(chloroethene)

Answer 6

It releases toxic HCl gas

Question 7

The Ozone layer is found in the __________. It is continually being formed and broken down by __ _________.
The ozone layer is very important to life on earth because it absorbs ___ radiation (which can cause sunburns and ___ ______) from the sun.

Answer 7

Stratosphere
UV radiation
UV-B
Skin Cancer

Question 8

What are the uses of chlorofluorocarbons?

Answer 8

• Refrigerants
• Air-conditioning
• Aerosol propellants
• Solvents

Question 9

What are the properties of chlorofluorocarbons?

Answer 9

• Volatile (have low b.p’s)
• stable/non-flammable
• non-toxic

Question 10

What are the problems with chlorofluorocarbons?

Answer 10

Long-lasting and catalyse the breakdown of the ozone layer.

Question 11

How do CFCs break down the ozone’s layer?

Answer 11

INITIATION
- A C-Cl bond breaks, forming a Cl radical.
CF2Cl2 —> .CF2Cl + .Cl
- This is triggered by UV light and takes place in the stratosphere.
- The C-Cl bond breaks as it has a lower bond enthalpy than C-F.

PROPAGATION
- The Cl radical reacts with O3
.Cl + O3 —> .ClO + O2
.ClO + O —> .Cl + O2

Overall Equation:
O3 + O —> 2O2

Question 12

What other radicals (other than CFCs) also catalyse the breakdown of the ozone layer and are produced in lightening strikes and jet engines? What are the propagation equations for this reaction?

Answer 12

.NO radicals (produced by O2 and N2)

.NO + O3 —> .NO2 + O2
.NO2 + O —> .NO + O2

O3 + O —> 2O2

Question 13

What are Haloalkanes?

Answer 13

A homologous series of organic compounds that contain a halogen.

Question 14

How are haloalkanes classified?

Answer 14

By the number of alkyl groups bonded directly to the halogen-bearing carbon.

(Primary = 0 or 1, Secondary = 2, Tertiary = 3)

Question 15

What do hydrolysis reactions involve? What type of reaction is it when haloalkanes are involved? What Is formed through this reaction?

Answer 15

The splitting of molecules with water to form new molecules.

It is a substitution reaction where a halogen is replaced by a hydroxyl group.

R-X + H2O —> R-OH + H+ + X-

Alcohols are formed.

Question 16

What does the rate of hydrolysis depend on?

Answer 16

The strength of the carbon-halogen bond.

E.g. C-F bonds are strongest and C-I are weakest. Therefore the trend in rate is iodoalkanes > bromoalkanes > chloroalkanes

Fluoroalkanes are unreactive as the C-F bond is so strong.

Question 17

What experiment can you do to investigate the differences in rates of reactions between haloalkanes?

Answer 17

Hydrolysis reactions of iodo, bromo and chloroalkanes in aqueous silver nitrate and ethanol. (Ethanol is added to help mix the water and haloalkane together).

As the reaction takes place halogen ions are produced which then make AgX precipitates.

Question 18

How can haloalkanes be converted to alcohols?

Answer 18

Using aqueous NaOH and heated under reflux.

Question 19

What is a nucleophile?

Answer 19

An electron pair donor (often delta negative)

Question 20

What happens in nucleophilic substitution? What is the name of the delta positive carbon centre?

Answer 20

Due to differences in electronegativity, carbon-halogen bonds are polar.

As electrons in the C-X bond are attracted to the halogen, this leaves the carbon with a positive dipole. The carbon is referred to as an electron-deficient centre.

Question 21

How are alcohols classified?

Answer 21

Primary, secondary or tertiary depending on the number of carbons attached to the carbon bonded to the -OH group

Question 22

What kind of intermolecular forces do alcohols have?

Answer 22

London forces and hydrogen bonds due to the -OH group

Question 23

Are Alcohols more or less soluble in water than alkanes? Why?

Answer 23

Alcohols are mole soluble in water than alkanes as alcohols are able to undergo hydrogen-bonding with water molecules.

Question 24

Do alcohols have higher or lower b.p’s than alkanes?

Answer 24

Alcohols have higher b.p’s than alkanes as they have hydrogen bonding as well as London forces while alkanes only have London forces.

Question 25

What is an elimination reaction?

Answer 25

The removal of a small molecule from a larger one. One reactant can form two products.

Question 26

What is dehydration? What are the conditions?

Answer 26

When alcohols lose water in an elimination reaction to form alkenes.

Conditions: H3PO4 / H2SO4 catalyst and heating by reflux

Question 27

What happens at a molecular level in dehydration of alcohols?

Answer 27

The OH group along with an adjacent H is lost, to form a water molecule. A double bond forms between the two carbons.

Question 28

Alcohols react with ______ ______ to form haloalkanes.

What are the conditions?

Answer 28

Hydrogen/Na halides

Conditions: Heat under reflux with H2SO4

Question 29

Alcohols always undergo ________ combustion.

Answer 29

Complete

Question 30

Acidified potassium dichromate changes colour from _____ to _____ when mixed with a primary or secondary alcohol.

Answer 30

Orange to green

Question 31

Primary alcohols can be oxidised to either _______ or ______ _____ depending on the conditions.

Secondary alcohols can be oxidised to _______.

Tertiary alcohols ______ be oxidised.

Answer 31

Aldehydes
Carboxylic acids

Ketones

Cannot

Question 32

What are the conditions needed to form an aldehyde from an alcohol? What does the aldehyde functional group look like?

Answer 32

Conditions: distil a primary alcohol with K2Cr2O7 and H2SO4

A carbon singly bonded to an H and doubly bonded to an O.

Question 33

What are the conditions needed to form an carboxylic acid from an alcohol? What does the carboxylic acid functional group look like?

Answer 33

Conditions: reflux a primary alcohol with K2Cr2O7 and H2SO4

A carbon doubly bonded to an O and singly bonded to an OH group.

Question 34

Excess oxidising agent is used to make _______ ______. ( 2[O] )

Answer 34

Carboxylic acid

Question 35

What are the conditions needed to form ketones from an alcohol? What does the ketone functional group look like?

Answer 35

Conditions: reflux a secondary alcohol with K2Cr2O7 and H2SO4

A carbon doubly bonded to an Oxygen

Question 36

Why does the C-Cl bond break instead of the C-F bond in CFCs when reacting with ozone?

Answer 36

Because it has a lower bond enthalpy (strength) than C-F.