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Question 1
In the reaction shown, reacts with bromomethane.
What is the role of in this reaction?
A.
Nucleophile, because it accepts an electron pair from carbon
B.
Electrophile, because it accepts the bromide ion
C.
Electrophile, because it donates a proton to bromomethane
D.
Nucleophile, because it donates a lone pair from nitrogen
Question 2
The reaction of chloroethane with cyanide ions is shown.
What is the leaving group?
A.
B.
C.
D.
Question 3
Chloride ion reacts with aluminium chloride to form .
What are the Lewis acid and Lewis base in this reaction?
A.
Lewis acid: ; Lewis base:
B.
Lewis acid: ; Lewis base:
C.
Lewis acid: ; Lewis base:
D.
Lewis acid: ; Lewis base:
Question 4
Bromomethane can undergo heterolytic fission of the C-Br bond.
What products are formed in this bond fission?
A.
B.
C.
D.
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Question 5
Ethene reacts with hydrogen bromide by electrophilic addition.
What is the electrophilic atom attacked first by the bond?
A.
The bromide ion formed
B.
A carbon atom in ethene
C.
The Br atom in
D.
The H atom in
Question 6
Propene reacts with bromine in the dark.
What is the organic product of this electrophilic addition reaction?
A.
B.
C.
D.
Question 7
A complex contains , five neutral ligands and one ligand.
What is the charge on the complex?
A.
B.
C.
D.
Question 8
Three primary halogenoalkanes, , and , react separately with aqueous hydroxide ions under the same conditions.
What is the expected order of increasing rate of substitution?
A.
B.
C.
D.
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Question 9
Ammonia reacts with bromomethane according to the equation:
State the nucleophile in this reaction.
[1]
Explain why this species acts as a nucleophile.
[1]
Question 10
Electrophiles can be positively charged or neutral species containing an electron-deficient atom.
State the electrophilic atom in hydrogen bromide when it reacts with an alkene.
[1]
Explain why can act as an electrophile.
[1]
Question 11
Hex-3-ene undergoes hydration in acidified conditions.
product
What is the product?
A.
B.
C.
D.
Question 12
1-bromobutane reacts with hydroxide ions mainly by an mechanism.
What combination is characteristic of this mechanism?
A.
Two steps; rate ; retention of configuration only
B.
Two steps; rate ; nucleophile absent from the rate-determining step
C.
One concerted step; rate ; inversion of configuration
D.
One concerted step; rate ; carbocation intermediate formed
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Question 13
2-methylpropene reacts with hydrogen bromide.
What is the major organic product?
A.
B.
C.
D.
Question 14
Aqueous sodium hydroxide reacts with chloroethane to form ethanol.
State the leaving group in this reaction.
[1]
Describe the movement of electron pairs during the substitution reaction.
[2]
Question 15
Iodomethane can undergo heterolytic fission of its carbon-iodine bond.
Define heterolytic fission.
[1]
Write an equation for the heterolytic fission of iodomethane and state the direction of the curly arrow.
[2]
Question 16
Pent-2-ene is shaken with bromine water in the dark.
Write the condensed structural formula of the organic product.
[1]
State the observation.
[1]
Explain why pentane does not give the same observation in the dark.
[1]
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Question 17
Several species were tested as possible nucleophiles in reactions with electron-deficient organic molecules.
Species tested | Bond formed with electron-deficient carbon? |
|---|---|
Yes | |
Yes | |
Yes | |
No | |
No |
Identify two species in the table that can act as nucleophiles.
[1]
Explain why can act as a nucleophile even though it is neutral.
[1]
Suggest why does not act as a nucleophile at nitrogen.
[1]
Question 18
Four possible representations of bond fission in bromomethane are shown.
Identify the diagram that represents heterolytic fission.
[1]
Write an equation for heterolytic fission of bromomethane.
[1]
Explain why the bromine-containing product has a negative charge.
[1]
Question 19
The flowchart summarizes addition reactions of symmetrical alkenes.
State the reaction type shown in all three branches of the flowchart.
[1]
Write an equation for the reaction of but-2-ene with hydrogen bromide.
[1]
Name the alcohol formed by hydration of hex-3-ene.
[1]
Explain why the bond in an alkene is susceptible to attack by electrophiles.
[1]
Question 20
Benzene reacts with a charged electrophile, , by electrophilic substitution rather than electrophilic addition.
What is the main reason substitution is favoured?
A.
Substitution restores the aromatic delocalized system after attack by
B.
Substitution occurs because benzene has localized C=C bonds like an alkene
C.
Substitution avoids formation of any carbocation intermediate
D.
Substitution breaks all six C-C bonds in the benzene ring
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Question 21
Hex-3-ene reacts with steam in the presence of an acid catalyst.
State the type of reaction.
[1]
Write the condensed structural formula of the alcohol formed.
[1]
Explain why only one structural alcohol is formed from hex-3-ene.
[1]
Question 22
Ammonia reacts with boron trifluoride to form a Lewis acid-base adduct.
Identify the Lewis acid and the Lewis base.
[2]
Draw the product, showing the coordination bond.
[1]
Question 23
Complex ions contain ligands bonded to a central transition element ion by coordination bonds.
Deduce the oxidation state of iron in .
[1]
Deduce the charge on if nickel is in the oxidation state.
[1]
Explain why acts as a ligand in transition metal complexes.
[1]
Question 24
Three halogenoalkanes, , and , are reacted separately with the same concentration of aqueous hydroxide ions under identical conditions.
State the order of increasing rate of nucleophilic substitution.
[1]
Explain the order in terms of the leaving group.
[2]
Write the rate equation expected for an reaction between bromoethane and hydroxide ions.
[1]
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Question 25
Chloroethane reacts with aqueous hydroxide ions in a nucleophilic substitution reaction.
State the leaving group in this reaction.
[1]
Draw curly arrows on the diagram to show the movement of electron pairs in the substitution reaction.
[2]
Explain why the carbon bonded to chlorine is attacked by the nucleophile.
[1]
Question 26
The table shows reactions involving electron-pair acceptors.
Reaction | Species / site markers |
|---|---|
1 | + (electron-poor B) |
2 | (carbonyl , ) |
3 | + (C=C bond; —) |
Identify the electrophile in the reaction between and .
[1]
Identify the electrophilic atom in a carbonyl compound shown in the table.
[1]
Explain why can provide an electrophilic site for reaction with an alkene.
[2]
Question 27
Samples of hydrocarbons were shaken with bromine water in the dark. The observations and structural formulas are shown.
Hydrocarbon | Structural formula | Observation with bromine water (dark) |
|---|---|---|
methane | orange remains orange | |
ethane | orange remains orange | |
ethene | orange turns colourless | |
propene | orange turns colourless |
State the type of hydrocarbon that decolourizes bromine water in the dark.
[1]
Deduce the product formed when ethene reacts with bromine.
[1]
Explain why an alkane does not decolourize bromine water in the dark under these conditions.
[2]
Write an equation for hydration of ethene to form the alcohol.
[1]
Question 28
Two reactions are represented using Lewis formulas.
Identify the Lewis base in both reactions.
[1]
Identify the Lewis acid in the reaction between and .
[1]
Compare the two reactions in terms of Brønsted-Lowry and Lewis acid-base theory.
[2]
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Question 29
The table shows several complex ions and the charges of their ligands.
Complex ion | Ligands present | Charge on each ligand |
|---|---|---|
4 chloride ligands () | each | |
1 hydroxide ligand (), 5 water ligands () | ; | |
6 ammonia ligands () | each |
State the role of a ligand in forming a complex ion.
[1]
Deduce the charge on when cobalt has oxidation state .
[1]
Deduce the oxidation state of iron in .
[1]
Explain why a transition metal cation can act as a Lewis acid in complex ion formation.
[1]
Question 30
Compound A is 1-bromopropane. Compound B is 2-bromo-2-methylpropane. Both react with aqueous hydroxide ions by nucleophilic substitution.
State the most likely mechanism for each compound.
[2]
Explain the different mechanisms in terms of structure.
[2]
Question 31
Propene reacts with hydrogen bromide by electrophilic addition.
State the major organic product.
[1]
Explain why this product is formed in greater amount than the alternative product.
[2]
Describe the electron-pair movement in the first step of the mechanism.
[1]
Question 32
Benzene reacts with a charged electrophile, , by electrophilic substitution.
Explain why benzene tends to undergo substitution rather than addition.
[1]
Draw the mechanism for the reaction of benzene with , using curly arrows.
[3]
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Question 33
The initial rate of hydrolysis of a tertiary halogenoalkane, , was measured at constant temperature with different concentrations of and hydroxide ions.
Run | / mol dm | / mol dm | Initial rate / mol dm s |
|---|---|---|---|
1 | 0.10 | 0.10 | |
2 | 0.20 | 0.10 | |
3 | 0.20 | 0.20 | |
4 | 0.30 | 0.30 |
Deduce the order of reaction with respect to .
[1]
Deduce the order of reaction with respect to .
[1]
Write the rate equation for the reaction.
[1]
Suggest the substitution mechanism consistent with the rate data.
[1]
Explain why the rate data are consistent with the mechanism suggested in (d).
[1]
Question 34
Comparable primary halogenoalkanes were reacted separately with the same nucleophile under identical conditions. The relative initial rates are shown.
State the order of increasing rate for the three halogenoalkanes.
[1]
Identify the best leaving group among , and .
[1]
Explain the trend in rate using bond strength.
[1]
Suggest why the primary halogenoalkanes are expected to react mainly by an mechanism.
[1]
Question 35
1-bromopropane reacts with hot aqueous sodium hydroxide to form propan-1-ol.
Consider the roles of the reacting species.
I.
Identify the nucleophile, the leaving group and the electrophilic atom in this reaction.
[3]
II.
Write an equation for the substitution reaction using structural formulas.
[1]
Explain the electron-pair movement involved in the reaction.
[3]
Question 36
Bond fission can produce either ions or radicals depending on how the bonding electrons are shared between the fragments.
Consider heterolytic fission of bromomethane.
I.
Define heterolytic fission.
[1]
II.
Write an equation for heterolytic fission of bromomethane.
[1]
III.
State where the curly arrow should start and end for this heterolytic fission.
[1]
Compare heterolytic fission with homolytic fission of a halogen molecule under ultraviolet light.
[3]
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Question 37
But-2-ene is used to make several products by addition reactions.
Deduce products formed when but-2-ene undergoes addition reactions.
I.
Write the equation for the reaction of but-2-ene with bromine.
[1]
II.
Write the equation for the reaction of but-2-ene with hydrogen bromide.
[1]
III.
Write the equation for hydration of but-2-ene.
[1]
IV.
State why only one structural product is expected in each reaction in (a)(ii) and (a)(iii).
[1]
A sample of but-2-ene and a sample of butane are each shaken with bromine water in the dark. Explain the difference in observations.
[3]
Question 38
Ammonia reacts with boron trifluoride to form the adduct .
Apply Lewis acid-base theory to this reaction.
I.
Identify the Lewis acid and Lewis base.
[2]
II.
Explain the electron-pair roles of the two species.
[1]
Draw the Lewis formula of the product, showing the origin of the coordination bond.
[2]
Explain why this reaction is not a Brønsted-Lowry acid-base reaction.
[2]
Question 39
Propene reacts with hydrogen bromide to form two structural isomers. The product distribution is shown.
State the major product of the reaction.
[1]
Identify the more stable carbocation intermediate formed in the first step.
[1]
Explain why the carbocation identified in (b) leads to the major product.
[2]
Draw curly arrows for the first step leading to the major-product carbocation.
[1]
Question 40
The mechanism of electrophilic substitution of benzene by a charged electrophile, , is represented in outline.
State why benzene usually undergoes substitution rather than addition.
[1]
Draw the curly arrow for the first step of the mechanism.
[1]
Explain why the intermediate shown is less stable than benzene.
[1]
Describe how aromaticity is restored in the second step.
[1]
Write the overall equation for electrophilic substitution of benzene by .
[1]
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Question 41
The ability of a species to donate or accept an electron pair determines its role in an electron-pair sharing reaction.
First reaction:
Second reaction:
Use the first and second reactions above to answer the following questions.
I.
Identify the nucleophile in the first reaction and explain your choice.
[2]
II.
Identify the electrophilic atom in the first reaction and explain your choice.
[1]
III.
Identify the electrophile in the first step of the second reaction.
[1]
Discuss the statement: “All negatively charged species are nucleophiles and all neutral species are not nucleophiles.”
[2]
Question 42
Alkenes are described as useful starting molecules because the carbon-carbon double bond can be converted into different functional groups.
Ethene is reacted separately with bromine, hydrogen chloride and water under suitable conditions.
I.
Deduce the product of the reaction with bromine.
[1]
II.
Deduce the product of the reaction with hydrogen chloride.
[1]
III.
Deduce the product of hydration.
[1]
Explain why the carbon-carbon double bond in ethene is susceptible to electrophilic attack.
[2]
Evaluate the use of bromine water as a test to distinguish an alkene from an alkane.
[3]
Question 43
Bromoethane can be converted into different organic products by reaction with nucleophiles.
Bromoethane is reacted separately with hydroxide ions and ammonia.
I.
Write an equation for the reaction with hydroxide ions.
[1]
II.
Write an equation for the reaction with ammonia to form the organic cation.
[1]
III.
Identify the nucleophile in each reaction.
[2]
Explain why both reactions are classified as nucleophilic substitution reactions.
[3]
Question 44
Transition element cations form complex ions with ligands such as , , and .
Deduce charges and oxidation states for complex ions.
I.
Deduce the charge on if cobalt is in the oxidation state.
[1]
II.
Deduce the oxidation state of iron in .
[1]
III.
Deduce the charge on if iron is in the oxidation state.
[1]
Explain the formation of in terms of Lewis acid-base theory.
[3]
Discuss whether a coordination bond is a different type of covalent bond after it has formed.
[2]
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Question 45
The rate of nucleophilic substitution depends on the identity of the halogen in a halogenoalkane. Three compounds, , and , are reacted separately with the same concentration of hydroxide ions under identical conditions.
Predict the relative rates for the three reactions.
I.
Rank the halogenoalkanes from fastest to slowest reaction.
[1]
II.
Identify the best leaving group among , and .
[1]
Explain the trend in rate in terms of bonding and ion stability.
[3]
Evaluate why the comparison is only valid when the organic group and reaction conditions are kept the same.
[2]
Question 46
1-bromobutane and 2-bromo-2-methylpropane react with aqueous hydroxide ions by different nucleophilic substitution mechanisms.
Compare the mechanisms and rate laws for the two halogenoalkanes.
I.
State the mechanism and rate equation expected for 1-bromobutane.
[2]
II.
State the mechanism and rate equation expected for 2-bromo-2-methylpropane.
[2]
Explain why the primary halogenoalkane favours the mechanism.
[2]
Explain why the tertiary halogenoalkane favours the mechanism.
[2]
Question 47
Symmetrical alkenes undergo electrophilic addition with halogens, hydrogen halides and water in acidified conditions.
Consider the addition of bromine to but-2-ene.
I.
Explain why bromine can act as an electrophile as it approaches the alkene.
[1]
II.
Draw the electron-pair movement for the first step of the mechanism.
[2]
Explain why addition of HBr to but-2-ene gives only one structural product, and state the product.
[2]
Describe the role of the acid catalyst in the hydration of a symmetrical alkene.
[3]
Question 48
Carbocation stability is used to explain the major products of addition reactions of unsymmetrical alkenes and the substitution reactions of benzene with electrophiles.
Propene reacts with hydrogen bromide.
I.
Predict the major product.
[1]
II.
Explain why this product is favoured.
[2]
Propene is hydrated in acidified conditions. Predict the major product and explain the role of water in the mechanism.
[2]
Discuss why benzene reacts with a charged electrophile, , by substitution rather than addition.
[3]
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