Chemistry 9701 · AS & A Level
Halogen compounds
100 practice questions on Halogen compounds, with worked solutions and instant marking.
Which statements can be used to explain the mechanism for the reaction of 1-chloropropane with ammonia?
Feb/March 2017
An organic ion that has a carbon atom carrying a negative charge is known as a carbanion. An organic ion that has a carbon atom carrying a positive charge is known as a carbocation. The reaction of aqueous sodium hydroxide with 1-bromobutane follows an $\text{S}_\text{N}2$ mechanism. What happens first in the mechanism?
Feb/March 2018
A reaction takes place when a sample of 1-chloropropane is heated under reflux with sodium hydroxide dissolved in ethanol. Which row is correct?
Feb/March 2018
A precipitate is formed when organic compound X is heated with aqueous silver nitrate. The precipitate then dissolves after concentrated aqueous ammonia is added. Which compound could X be?
Feb/March 2018
How many structural isomers exist for trichloropropane, $\text{C}_3\text{H}_5\text{Cl}_3$?
Feb/March 2019
The reaction of bromopropane with water is shown here. $\text{CH}_3\text{CH}_2\text{CH}_2\text{Br} + \text{H}_2\text{O} \rightarrow \text{CH}_3\text{CH}_2\text{CH}_2\text{OH} + \text{HBr}$ Which statement is right?
Feb/March 2019
Compound Y is heated with an excess of dry HBr. What is the main product formed in the reaction?
Feb/March 2020
What observations are seen when a sample of silicon chloride, $\text{SiCl}_4$, is added to a beaker containing water?
Feb/March 2021
In which reactions is the chief product made by a nucleophilic substitution reaction?
Feb/March 2021
A reaction takes place when a sample of 1-chloropropane is warmed under reflux with sodium hydroxide dissolved in ethanol. Which row is correct?
Feb/March 2022
Compound X, $\text{C}_7\text{H}_{13}\text{Br}$, undergoes reaction with hot alcoholic NaOH to form two products, Y and Z. When Y is reacted with $\text{Br}_2$, it forms a product, $\text{C}_7\text{H}_{12}\text{Br}_2$, that is present as a mixture of four optical isomers. When Z is reacted with $\text{Br}_2$, it forms a product, $\text{C}_7\text{H}_{12}\text{Br}_2$, that is non-chiral. What might X be?
Feb/March 2023
Which compound undergoes reaction most rapidly with aqueous silver nitrate via an $\text{S}_\text{N}1$ mechanism?
Feb/March 2023
During the hydrolysis of bromoethane with aqueous NaOH, what are the identities of the attacking group and the leaving group?
Feb/March 2024
Only structural isomerism should be taken into account when answering this question. How many compounds having molecular formula $\text{C}_5\text{H}_{11}\text{Br}$ are primary halogenoalkanes?
Feb/March 2024
Compound Y is broken down by warm aqueous silver nitrate to give a precipitate that dissolves in dilute aqueous ammonia. Compound Y then undergoes an elimination reaction to produce an alkene. What is the skeletal formula for compound Y?
Feb/March 2025
Propan-2-ol can be changed into 2-chloropropane by using reagent M first and then reagent N. Which row is correct?
Feb/March 2025
1-chloro-2-methylpropane and 2-bromo-2-methylbutane are each reacted separately with aqueous silver nitrate in ethanol. In both cases, nucleophilic substitution occurs and a precipitate is produced. The time needed for 1-chloro-2-methylpropane to produce a precipitate is $T_1$. The time needed for 2-bromo-2-methylbutane to produce a precipitate is $T_2$. Which row is correct?
Feb/March 2025
In a number of countries, plastic waste is gathered separately and then sorted. A proportion of it is burned to supply heat for power stations. Why is pvc, polyvinylchloride, taken out of any waste before it is burned?
May/June 2010
Which of these reactions are instances of nucleophilic substitution?
May/June 2010
In many nations, plastic waste is gathered separately and sorted. A portion of this is burned to generate heat for power stations. Why is pvc, polyvinylchloride, taken out of any waste that is to be incinerated?
May/June 2010
Which of these reactions are instances of nucleophilic substitution?
May/June 2010
In a number of countries, plastic waste is gathered separately and then sorted. Part of it is burnt to generate heat for power stations. Why is PVC, polyvinylchloride, taken out of any waste that will be incinerated?
May/June 2010
Which halogenoalkane reacts by an $S_N1$ mechanism and forms a yellow precipitate when $\text{AgNO}_3\text{(aq)}$ is added?
May/June 2011
Which reaction would produce 2-chloropropane in the highest yield?
May/June 2011
$1,1$-dichloropropane reacts with aqueous sodium hydroxide through a sequence of steps to produce propanal. $\text{CH}_3\text{CH}_2\text{CHCl}_2 \xrightarrow{\text{NaOH(aq)}} \text{CH}_3\text{CH}_2\text{CHO}$ Which term is used to describe the first stage of this reaction?
May/June 2011
Bromoethane goes through every conversion shown. Which of these conversions are instances of nucleophilic substitution?
May/June 2011
Halogenoalkanes have long been used for many years as aerosol propellants, refrigerants and solvents. Fluoroethane, $\text{CH}_3\text{CH}_2\text{F}$, has been used as a refrigerant and can be prepared by reacting ethene with hydrogen fluoride. Your task is to calculate the C-F bond energy in fluoroethane.
May/June 2011
A halogen in an organic compound can be detected by heating the organic compound with aqueous silver nitrate. Which compound would form a precipitate most rapidly?
May/June 2012
When the ozone layer in the upper atmosphere is reduced, Earth’s natural shield against harmful ultraviolet radiation becomes weaker. Which compound would lead to the greatest depletion of the ozone layer?
May/June 2012
When phenacyl chloride, $\text{C}_6\text{H}_5\text{COCH}_2\text{Cl}$, reacts with aqueous NaOH, this substitution proceeds by an $\text{S}_\text{N}2$ mechanism. Which structure shows a species produced in the reaction?
May/June 2012
Coniine is the principal component of the poison known as ‘oil of hemlock’. Coniine may be prepared by allowing ammonia to react with a dibromo compound, $X$. $\text{NH}_3 + \text{C}_8\text{H}_{16}\text{Br}_2 \rightarrow \text{coniine} + 2\text{HBr}$ What is the name of compound $X$?
May/June 2012
When the ozone layer in the upper atmosphere is depleted, Earth’s natural shield against harmful ultraviolet radiation is weakened. Which compound would lead to the greatest depletion of the ozone layer?
May/June 2012
Aqueous sodium hydroxide reacts with $1$-bromopropane to form propan-$1$-ol. What is the correct description of the first step in the mechanism?
May/June 2013
In the mixture formed during the photochemical chlorination of methane, which molecules would be found?
May/June 2013
Compound $Y$ may be hydrolysed using warm aqueous silver nitrate, producing a precipitate that dissolves in dilute aqueous ammonia. Compound $Y$ is also able to take part in an elimination reaction to give an alkene. What might be the skeletal formula of compound $Y$?
May/June 2013
What properties do fluoroalkanes have?
May/June 2013
What sequence of reagents can be used in the laboratory to change propan-1-ol into 2-bromopropane?
May/June 2013
A carbanion is an organic ion that has a negative charge on a carbon atom. A carbocation is an organic ion that has a positive charge on a carbon atom. What steps are involved in the mechanism of the reaction between aqueous sodium hydroxide and 2-bromo-2-methylbutane?
May/June 2013
$\text{CCl}_2\text{FCClF}_2$ may be changed into $\text{CH}_2\text{FCF}_3$ by the route shown below. Stage 1: $\text{CCl}_2\text{FCClF}_2 \rightarrow \text{CCl}_2\text{CF}_3$ Stage 2: $\text{CCl}_2\text{CF}_3 \rightarrow \text{CCl}_2\text{FCF}_3$ Stage 3: $\text{CCl}_2\text{FCF}_3 \rightarrow \text{CH}_2\text{FCF}_3$ What type of reaction occurs in stage 1?
May/June 2013
Fabrics used for aircraft seating are given a coating that contains a halogenoalkane. Why is this coating applied?
May/June 2013
Halogenoalkanes take part in a variety of nucleophilic substitution reactions. Which reaction occurs only through an S$_\text{N}1$ mechanism?
May/June 2014
If halogenoalkanes are heated in ethanol containing KOH, they can undergo elimination to produce alkenes. Which elimination products may be formed if 2-bromobutane is heated with KOH dissolved in ethanol?
May/June 2014
When ultraviolet light is present, ethane reacts with chlorine to form a mixture of products. Which compound might be found in that mixture of products?
May/June 2014
Cyclic compound M is heated with dilute hydrochloric acid. Which products are formed in the reaction?
May/June 2015
Coniine is the principal component of the poison ‘oil of hemlock’. Coniine can be made by reacting ammonia with a dibromo compound, $X$. $\text{NH}_3 + \text{C}_8\text{H}_{16}\text{Br}_2 \rightarrow \text{coniine} + 2\text{HBr}$ What is the name of compound $X$?
May/June 2015
2-bromopropane is heated with a concentrated solution of sodium hydroxide in ethanol. Which substance is the main product formed in this reaction?
May/June 2015
Which compounds undergo reaction with HBr to form the compound R?
May/June 2015
Halogenated hydrocarbons have many uses. For what purposes have halogenated hydrocarbons been used?
May/June 2015
In the laboratory, the labels had come off four bottles. A student noticed that the substance in one of them could be recognised quite easily, since when water was added it would not release fumes of hydrogen chloride. Which one did not produce the $\text{HCl}$ fumes?
May/June 2015
What kinds of reaction does $\text{CH}_2\text{BrCHCH}_2$ undergo?
May/June 2015
What reaction types may happen with 1-bromobutane?
May/June 2016
Chlorofluorocarbons harm the ozone layer by reacting through a free radical mechanism. The initial step in this process is initiation. Which equation is most likely to represent the initiation step when chlorofluoromethane is involved in such a reaction?
May/June 2016
1-chloro-1-methylcyclohexane is hydrolysed by heating with $\text{NaOH(aq)}$. The reaction pathway is illustrated below. In 1-chloro-1-methylcyclohexane, one carbon atom is attached to three other carbon atoms. What charge does this carbon atom have at point Z?
May/June 2016
Which reaction would produce 2-chloropropane in the highest yield?
May/June 2016
The reaction of NaOH(aq) with the three chloroalkanes shown is considered below. $\text{CH}_3\text{CH}_2\text{CHClCH}_3$ \quad $(\text{CH}_3)_2\text{CHCH}_2\text{Cl}$ \quad $(\text{CH}_3)_3\text{CCl}$ Which of these statements are correct?
May/June 2017
Which equation shows the initiation step in the substitution reaction of methane with chlorine?
May/June 2017
When aqueous sodium hydroxide reacts with 1-bromopropane to form propan-1-ol, what needs to be shown in a diagram for the first step in the mechanism?
May/June 2017
When heated under reflux with an aqueous solution of sodium hydroxide, 2-bromo-2-methylpropane undergoes nucleophilic substitution. Which row is correct?
May/June 2017
A test-tube containing $\text{HBr(g)}$ and another separate test-tube containing $\text{HI(g)}$ are heated until both reach the same temperature. Which set of observations could be seen?
May/June 2017
Which compounds, when heated in ethanolic NaOH, yield more than one product with molecular formula $\text{C}_4\text{H}_8$?
May/June 2017
Sodium methoxide, $\text{Na}^+\text{CH}_3\text{O}^-$, undergoes nucleophilic substitution with 2-chloro-2-methylpropane. The nucleophile is the $\text{CH}_3\text{O}^-$ ion. Which row is correct?
May/June 2018
When working through this question, take into account structural isomerism and stereoisomerism. A colourless liquid, $\text{C}_5\text{H}_{11}\text{Cl}$, occurs as a mixture of two optical isomers. If it is heated with sodium hydroxide in ethanol, just a mixture of two alkenes is produced. What might the colourless liquid be?
May/June 2018
If warm water is introduced to halogenoalkane X, an $S_N1$ reaction takes place. $\text{AgNO}_3(aq)$ is then added, and a yellow precipitate appears. What could X be?
May/June 2018
A has the formula $\text{CH}_3\text{CHBrCH}_2\text{CH}_3$.
May/June 2018
The Finkelstein reaction takes place when NaI in propanone is used with either a chloroalkane or a bromoalkane. The halogen atom is replaced directly by I. This reaction functions only with primary halogenoalkanes. Which halogenoalkane gives compound X?
May/June 2019
Water is added to a sample of $2,3$-dibromohexane. Some of the $2,3$-dibromohexane is completely hydrolysed, while the rest is only partially hydrolysed. Which substance is absent from the mixture of products?
May/June 2019
Halogenoalkanes undergo nucleophilic substitution reactions with various reagents.
May/June 2019
2-bromo-2-methylpentane is a tertiary halogenoalkane. Which organic products are produced when 2-bromo-2-methylpentane is reacted with a hot concentrated ethanolic solution of sodium hydroxide?
May/June 2020
What is the principal product Z formed in the reaction shown below? The compound given reacts with an excess of dry HBr when warmed, producing Z.
May/June 2020
1,2-dibromopropane may be prepared from 1-bromopropane in two steps. Which row is correct?
May/June 2020
A reaction mechanism is illustrated. (Reaction scheme showing a cyclic chloroalkane reacting with $\text{OH}^-$ to form an alcohol and $\text{Cl}^-$.) Which of the following statements about this reaction are correct?
May/June 2020
(a) A bottle without a label contains the straight-chain halogenoalkane Q. The molecular formula of Q is $\text{C}_5\text{H}_{11}X$, where $X$ is a halogen; bromine, chlorine or iodine. A test is used to identify which halogen is in Q. A portion of Q is added to NaOH(aq) and heated. Dilute nitric acid is then added, followed by a few drops of aqueous silver nitrate. A cream precipitate forms.
May/June 2020
Cyanide ions react with bromoethane, giving propanenitrile. Which statement correctly describes the $\text{S}_\text{N}2$ mechanism for this reaction?
May/June 2021
In a nucleophilic substitution reaction, sodium methoxide, $\text{Na}^+\text{CH}_3\text{O}^-$, undergoes reaction with 2-chloro-2-methylpropane. The $\text{CH}_3\text{O}^-$ ion acts as the nucleophile. Which row is correct?
May/June 2021
Halogenoalkanes are attacked by nucleophiles such as $\text{OH}^-$. Which two halogenoalkanes both undergo an $S_\text{N}1$ mechanism?
May/June 2021
Depending on the solvent used, Bromoethane reacts with NaOH in different ways. Which of the following rows about these reactions is correct?
May/June 2021
An excess amount of 2-bromo-2-methylpropane is mixed with $0.0010\,\text{mol}$ of $\text{NaOH}(aq)$, together with a few drops of phenolphthalein indicator. As soon as mixing begins, a stopwatch is started. The interval for the pink colour to vanish is then noted. The test is carried out again at other temperatures, while the concentrations and volumes of all reagents are kept the same.
May/June 2021
Ethanol may be transformed into propanenitrile in two stages. $\text{CH}_3\text{CH}_2\text{OH} \xrightarrow{X} \text{CH}_3\text{CH}_2\text{Br} \xrightarrow{Y} \text{CH}_3\text{CH}_2\text{CN}$. What types of reaction are $X$ and $Y$?
May/June 2022
The diagram illustrates the structures of two halogenoalkanes, P and Q. Both compounds can undergo hydrolysis. Which row is correct?
May/June 2022
When Compound J, $\text{C}_{15}\text{H}_{23}\text{Br}_2\text{Cl}$, is treated with an excess of hot concentrated sodium hydroxide solution in ethanol, one product formed is X. Which skeletal formula could represent X?
May/June 2022
Under ultraviolet light, bromine reacts with butane to make bromobutane. This reaction gives two structural isomers with the molecular formula $\text{C}_4\text{H}_9\text{Br}$.
May/June 2022
Fig. 5.1 illustrates three reactions involving 2-bromopropane, $\text{CH}_3\text{CH(Br)CH}_3$.
May/June 2022
2-methylpropene reacts with $\text{HCl}(g)$ at room temperature, and the main organic product formed is 2-chloro-2-methylpropane.
May/June 2022
Which row states the solvent employed and the kind of reaction taking place when bromoethane reacts with NaOH to make ethene?
May/June 2023
Which statement explains the change that occurs when 2-chloro-2-methylpropane is warmed with NaOH(aq)?
May/June 2023
When ethane reacts with an excess of chlorine in ultraviolet light, a mixture of products is produced. How many of these products have two carbon atoms and one or more chlorine atoms?
May/June 2023
Halogenoalkanes undergo reaction with hot ethanolic potassium cyanide. The mechanism for this reaction is either $\text{S}_\text{N}1$ or $\text{S}_\text{N}2$. Which statement is true?
May/June 2023
A mixture of ethane and an excess of chlorine is exposed to UV light. How many different products, each with only two carbon atoms and at least one chlorine atom in each molecule, could be formed?
May/June 2023
What reaction takes place when ethane and chlorine are mixed in diffused sunlight?
May/June 2024
Q is a halogenoalkane that is either primary or tertiary. It is hydrolysed by aqueous sodium hydroxide. In the first stage of the mechanism for this reaction, two species react with each other. Which row is correct?
May/June 2024
2-bromopropane is changed into 1,2-dibromopropane by a route with two reactions. reaction 1: 2-bromopropane $\rightarrow$ compound X reaction 2: compound X $\rightarrow$ 1,2-dibromopropane What reagents and conditions are required for the two reactions?
May/June 2024
What reagents could be used to make 2-bromobutane from butan-1-ol?
May/June 2024
Compound X is reacted with an excess of dilute aqueous potassium hydroxide. What structure is formed for the organic product?
May/June 2024
1-bromopropane undergoes reaction with hot ethanolic $\text{NaOH}$. What is the molecular formula for the product formed in this reaction?
May/June 2024
Which statement is right?
May/June 2024
On heating with $\text{KOH}$ dissolved in ethanol, halogenoalkanes may undergo elimination, producing alkenes. What elimination products are possible if $2$-bromobutane is heated with $\text{KOH}$ dissolved in ethanol?
May/June 2024
Chloroethane may be converted into sodium propanoate. $\text{chloroethane} \rightarrow \text{intermediate Q} \rightarrow \text{sodium propanoate}$ Intermediate Q is then hydrolysed using boiling aqueous $\text{NaOH}$ to form sodium propanoate. Which reagent would be used to prepare intermediate Q from chloroethane?
May/June 2024
$\text{CH}_3(\text{CH}_2)_5\text{CHBrCH}_3$ occurs as a pair of stereoisomers.
May/June 2024
Which statement about the mechanism of an $\text{S}_\text{N}1$ reaction involving a halogenoalkane is correct?
May/June 2025
Four separate drops of 1-chlorobutane, 1-bromobutane and 1-iodobutane are each introduced into three test-tubes containing $1.0\,\text{cm}^3$ of aqueous silver nitrate at $60^\circ\text{C}$. In each instance, hydrolysis occurs. $\text{H}_2\text{O(l)} + \text{R-X(l)} + \text{Ag}^+\text{(aq)} \rightarrow \text{R-OH(aq)} + \text{AgX(s)} + \text{H}^+\text{(aq)}$. $\text{R}$ represents $\text{C}_4\text{H}_9$ and $\text{X}$ represents the halogen atom. The rate at which cloudiness forms in the test-tubes is in the order $\text{RCl} < \text{RBr} < \text{RI}$. Why does this happen?
May/June 2025