Exam code: H032
This question is about alkenes.
Alkenes such as ethene and 2-methylbut-2-ene are unsaturated molecules.
What is meant by the term unsaturated?
The displayed formula of ethene is shown below.
State the value for the bond angle labelled a.
Explain, with the aid of a sketch, how p orbitals are involved in the formation of the double bond in an alkene.
Explain why ethene would be susceptible to attack from electrophiles.
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This question is about the reactions of propene.
Complete the flowchart below to show the major organic product formed in each of the addition reactions.
Use ‘curly’ arrows to complete the mechanism for the formation of the major product when propene CH3CH=CH2, reacts with hydrogen bromide, HBr.
Draw the displayed formula of the minor product formed from the reaction of propene and hydrogen bromide.
Explain why there is a major and minor product formed from the reaction between propene and hydrogen bromide.
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This question is about the isomers of butene.
Butene, C4H8, can exist as three isomers.
Describe a chemical test, including the expected observation, that will give a positive result for all isomers.
Butene can exist as different isomers.
Isomer A is a position isomer of isomers B and C and does not show E or Z isomerism. Isomer B is the Z isomer. Isomer C is the E isomer.
i) Draw the displayed formulae of the three isomers, A, B and C, of butene, C4H8.
[3]
ii) Name all three isomers, A, B and C, of butene, C4H8.
[3]
Draw the structural formula of the addition polymer formed by isomer A.
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This question is about isomers.
Diols are chemicals with two hydroxyl functional groups in their structures. A range of diols are shown in Figure 1.
Figure 1
Suggest why compounds A and B are the same compound but compounds C and D are isomers.
Name compounds C and D from Figure 1 using the E / Z naming system.
Compound G, shown in Figure 2, is a derivative of compound C.
Figure 2
Compound G
Suggest why the cis / trans naming system fails with compound G.
Ethanol can be formed by the hydration of ethene in the presence of a concentrated sulfuric acid catalyst at 300 °C.
Complete the mechanism in Figure 3 by using 'curly arrows' and adding relevant δ- and δ+ charges.
Figure 3
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This question is about different polymers.
Polymer X can be formed from an alkene.
Polymer X
i) State the type of polymerisation involved in the formation of polymer X.
[1]
ii) Draw the monomer used to form polymer X.
[1]
iii) Name polymer X.
[1]
Suggest three reasons why the disposal of polymer X would prove to be a challenge.
State which method of recycling heats the polymer to a high temperature so that it breaks down into the original monomer.
Polyesters and polyamides are condensation polymers and are biodegradable.
State the name of the process that breaks down these polymers.
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This question is about alkanes and alkenes.
Crude oil contains a mixture of hydrocarbons. These hydrocarbons are first separated in a process called fractional distillation.
The longer hydrocarbon chains are then cracked to shorter saturated and unsaturated hydrocarbons.
Figure 1 below shows two hydrocarbons that are obtained by cracking crude oil.
Figure 1
i) State which hydrocarbon is unsaturated and explain why.
[2]
ii) State which hydrocarbon is more reactive and explain why.
[3]
Draw the structure of ethane and ethene and include the bond angles.
Name and explain the geometry around the carbon atoms of each molecule.
Figure 2 shows alkenes B, C, D, E and F.
Figure 2
You will have to refer to these alkenes throughout this part of the question.
Describe, using the orbital overlap model, how the π-bond in alkene D is formed.
Many alkenes show E/Z isomerism.
i) Explain why E/Z isomerism is shown in some alkenes.
[2]
ii) From Figure 2, identify the two alkenes that exist as a pair of E/Z isomers.
[1]
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This question is about the preparation of alcohols.
Alcohols are valuable organic compounds which are often used as solvents, fuels and chemical feedstock. Alcohols can be prepared from the electrophilic addition reaction of alkenes.
The first step in this reaction involves the reaction of sulfuric acid with an alkene.
i) State what the electrophile is in this electrophilic addition reaction.
[1]
ii) Outline the mechanism for the reaction of but-1-ene with sulfuric acid to show the formation of the major product. Include the partial charges.
[4]
The reaction described in part (a) also produces a product in which the sulfate group is bonded to a less substituted carbon atom.
State the name and draw the structure of this product. State whether this is the minor or major product and explain why.
The following molecule shows E/Z isomerism.
Use the Cahn–Ingold–Prelog priority rules to identify whether this alkene is an E or Z stereoisomer. Explain how you came to your decision.
Which of the bond(s) shown in the following structure is/are in the Z configuration?
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This question is about polymers.
Figure 1 shows a section of the PVC polymer.
Figure 1
i) Draw the repeating unit of PVC.
[1]
ii) Draw the structure and state the name of the monomer of the PVC polymer.
[2]
iii) Write the equation to represent the formation of PVC from its monomer.
[1]
Polymers are unreactive compounds due to their long non-polar chain of saturated carbon-carbon and carbon-hydrogen bonds.
Although this means that they are safe to use, it also means that they are non-biodegradable, as they are not attacked by biological agents such as enzymes.
Table 1 below shows three different ways in which polymers can be disposed of.
Table 1
Method of disposal | Disadvantage |
Recycling |
|
Incineration |
|
Landfill sites |
|
State the disadvantage of each method of disposal to complete the table.
This part of the question is about 2-chloropropene, C3H5Cl. Three reactions of 2-chloropropene are shown in the flowchart below.
Complete the flowchart to show the organic products formed in the reactions
2-chloropropene can be polymerised to form poly(2-chloropropene).
i) Write a balanced equation for the formation of this polymer. The equation should include the structure of the repeating unit of the polymer.
[2]
ii) After their useful life, waste polymers can be disposed of by combustion.
State one particular problem with disposal of poly(2-chloropropene) by combustion.
[1]
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This question is about the preparation of alcohols.
Alcohols can be prepared via the electrophilic addition reaction of alkenes.
The first step involves the alkene reacting with sulfuric acid.
i) State what the electrophile is in this electrophilic addition reaction.
[1]
ii) Outline the mechanism for the reaction of but-1-ene with sulfuric acid to show the formation of the major product.
Include the partial charges.
[4]
The reaction described in part (a) also produces a product in which the sulfate group is bonded to a less substituted carbon atom.
i) State the name and draw the structure of this product.
[2]
ii) State whether this is the minor or major product and explain why.
[2]
The electrophilic addition reaction of sulfuric acid with but-1-ene results in the formation of three isomeric products.
Draw the structures of these isomeric products.
The second step in the formation of an alcohol from an alkene is the hydrolysis of the alkyl hydrogen sulfate formed in the first step.
i) Write the equation for this step of the reaction using the displayed formulae of the reactants and products.
[1]
ii) Draw the skeletal formulae of all structural isomers of the compound formed in this reaction.
[3]
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This question is about polymers.
Poly(methyl methacrylate) is used as a glass substitute in Perspex.
A section of the polymer chain is shown below.
Draw the skeletal formula of the monomer.
Explain why poly(methylmethacrylate) is fairly unreactive.
Polymer waste has been an environmental concern for many years now.
The availability, cost and convenience of polymers for use in many everyday household items mean the demand for them has increased bringing with it huge environmental effects.
Evaluate the three methods below for reducing the environmental impact of plastics.
Recycling
Combustion
Feedstock recycling
Bioplastics, such as biodegradable plastics offer a sustainable alternative to oil based products.
Where the use of plant based polymers is not possible, photodegradable polymers are being developed.
i) Explain how photodegradable polymers are broken down.
[1]
ii) Suggest two disadvantages of using photodegradable polymers.
[2]
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This question is about alkenes.
But-1-ene is an organic compound widely used in the petrochemical industry.
Explain why but-1-ene is more reactive than butane.
But-1-ene has the molecular formula C4H8.
For the reactions of but-1-ene with bromine, hydrogen bromide and steam:
Predict the organic products made
Write the equation for the reactions
Give the conditions for the reactions.
During the reaction between but-1-ene and HBr, the HBr breaks by heterolytic fission.
i) Explain what is meant by heterolytic fission.
[1]
ii) Draw the mechanism for the electrophilic addition of HBr to but-1-ene to show the formation of the major product.
[4]
The structure of but-2-en-1-ol is shown below.
For each labelled angle, state the bond angle and shape. Explain the shape around the atom.
You should refer to electron repulsion theory in your answer.
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