Chemistry 9701 · AS & A Level
Carbonyl compounds
100 practice questions on Carbonyl compounds, with worked solutions and instant marking.
Compound X has molecular formula C$_3$H$_6$O$_3$. When X is heated under reflux with acidified K$_2$Cr$_2$O$_7$, HO$_2$CCOCO$_2$H is formed. If X reacts with NaBH$_4$, HOCH$_2$CH(OH)CH$_2$OH is produced. Which structural formula could X have?
Feb/March 2016
The reaction scheme shows a number of reactions of compound P, $\text{C}_5\text{H}_8\text{O}$.
Feb/March 2016
Diols in which both hydroxy groups are attached to the same carbon atom can spontaneously lose a molecule of water to form a carbonyl compound. Which compound, after complete hydrolysis, gives a positive result with Tollens’ reagent?
Feb/March 2017
$\text{CH}_3\text{CH}_2\text{COCH}_2\text{CH}_3$ reacts with hydrogen cyanide to produce an organic compound known as a cyanohydrin. Which statement is correct?
Feb/March 2017
Compound X, $\text{CH}_3\text{CH(OH)CH(CHO)CH}_3$, is refluxed with an excess of acidified $\text{K}_2\text{Cr}_2\text{O}_7$ so that compound Y is produced. X and Y are then each warmed separately with Fehling’s solution and the observations recorded. What are the observations?
Feb/March 2017
Which compounds produce a pale yellow precipitate of tri-iodomethane when they react with alkaline aqueous iodine?
Feb/March 2017
Which compound gives a reaction with 2,4-dinitrophenylhydrazine reagent but shows no reaction with Tollens’ reagent?
Feb/March 2018
When compound X is heated under reflux with acidified potassium dichromate(VI), a carboxylic acid is formed. Compound X does not react with sodium metal. What might compound X be?
Feb/March 2018
Propanal reacts with hydrogen cyanide to give 2-hydroxybutanenitrile. A suitable catalyst for this reaction is sodium cyanide. $\text{CH}_3\text{CH}_2\text{CHO} + \text{HCN} \xrightarrow{\text{NaCN}} \text{CH}_3\text{CH}_2\text{CH(OH)CN}$. Which of the following statements about the reaction of propanal with hydrogen cyanide are correct?
Feb/March 2018
The compounds below are treated with hydrogen cyanide. Which compounds form a molecule with a chiral centre?
Feb/March 2019
P, Q and R each have five carbon atoms. A student performs a number of tests to tell P, Q and R apart.
Feb/March 2019
Which compounds give a yellow precipitate when tested with alkaline aqueous iodine?
Feb/March 2020
The diagram illustrates how compound $Y$ is formed from compound $X$ in a chemical reaction. $R_1$ and $R_2$ are alkyl groups. $X + \text{HCN} \xrightarrow[{}]{\text{KCN}} Y$ Which row correctly describes this reaction?
Feb/March 2021
For this question, you may assume that $^1\text{H}$ and $^3\text{H}$ show identical chemical behaviour. A sample of ethanal contains only the hydrogen isotope $^1\text{H}$. It is converted into compound $Z$, $\text{C}_2\text{H}_6\text{O}$, by a nucleophilic addition reaction with NaBH$_4$. Every hydrogen atom in the NaBH$_4$ is the $^3\text{H}$ isotope. $\text{CH}_3\text{CHO} \xrightarrow[]{\text{NaBH}_4} \text{C}_2\text{H}_6\text{O}$ Compound $Z$ is then oxidised to ethanal and water. $\text{C}_2\text{H}_6\text{O} + [O] \rightarrow \text{CH}_3\text{CHO} + \text{H}_2\text{O}$ Which statement about the final product mixture is correct?
Feb/March 2021
There are two carbonyl compounds with the molecular formula $\text{C}_3\text{H}_6\text{O}$. Which reagents produce different observations for these two compounds?
Feb/March 2021
Hydroxyethanal, $\text{HOCH}_2\text{CHO}$, has been detected in dust clouds close to the centre of our galaxy.
Feb/March 2021
Which compound produces both: • an orange precipitate when tested with 2,4-DNPH reagent • and a yellow precipitate with alkaline $I_2(aq)$?
Feb/March 2022
Compound Y is warmed using a mild oxidising agent. One of the reaction products then reacts with hydrogen cyanide to produce 2-hydroxybutanenitrile. What is compound Y?
Feb/March 2022
Alkenes react by addition with a $1{:}1$ blend of $ ext{CO}$ and $ ext{H}_2$ to give aldehydes. Fig. 3.1 illustrates the reaction of propene with a $1{:}1$ blend of $ ext{CO}$ and $ ext{H}_2$.
Feb/March 2023
For which pair will each compound produce a different observable outcome with alkaline I$_2$(aq)?
Feb/March 2024
Which reagent produces a positive test for propanone?
Feb/March 2024
What mechanism describes the reaction between hydrogen cyanide and propanone?
Feb/March 2025
The diagram illustrates the structure of progesterone. Which of the following statements about progesterone is correct?
Feb/March 2025
Fig. 4.1 presents compounds J to M, and each contains four carbon atoms.
Feb/March 2025
Which reagent produces similar results with both butanone and butanal?
May/June 2010
When propanone is refluxed with a solution of $\text{NaBH}_4$, what is formed?
May/June 2010
Which reagent would produce comparable results for both butanone and butanal?
May/June 2010
What product is produced when propanone is refluxed with a solution of $\text{NaBH}_4$?
May/June 2010
Which product is produced when propanone is refluxed with a solution of $\text{NaBH}_4$?
May/June 2010
Which reagent would produce similar outcomes with both butanone and butanal?
May/June 2010
Compound X makes warm acidified sodium dichromate(VI) change from orange to green. $1$ mol of X reacts with $2$ mol of $\text{HCN}$ in the presence of $\text{KCN}$. What could X be?
May/June 2011
Aldehydes and ketones are carbonyl compounds. Which of these react with $\text{NaBH}_4$ and also react with Fehling’s reagent?
May/June 2011
Sorbitol is an artificial sweetener that is used to sweeten chocolate and is suitable for diabetics. Which functional groups may be formed when this molecule is oxidised under suitable conditions?
May/June 2011
Which formulae indicate that propanone and propanal are different compounds?
May/June 2011
For the reaction of an aldehyde with $\text{HCN}$, with $\text{NaCN}$ as the catalyst, which of the following statements about the reaction mechanism are correct?
May/June 2011
Compound X causes warm acidified sodium dichromate(VI) to change from orange to green. When 1 mol of X is reacted with 2 mol of HCN in the presence of KCN. What may X be?
May/June 2011
Ketones are used extensively as solvents and as starting materials in the chemical industry. They contain the reactive keto group, $\mathrm{C{=}O}$. Propanone, $\mathrm{CH_3COCH_3}$, reacts with hydrogen cyanide, $\mathrm{HCN}$.
May/June 2011
Which compound, when it reacts with hydrogen cyanide, gives a product that contains a chiral centre?
May/June 2012
Which one of these compounds can be oxidised by acidified dichromate(VI) solution and also produces a positive result with Tollens’ reagent?
May/June 2012
The compound cis-hex-3-enal gives cut grass its distinctive smell. The human nose is especially sensitive to this compound and can detect $0.25$ parts per billion in air. Which reagents will react with cis-hex-3-enal?
May/June 2012
An industrial solvent that is widely used contains a blend of propanone, $\text{CH}_3\text{COCH}_3$, and pentyl ethanoate, $\text{CH}_3\text{CO}_2(\text{CH}_2)_4\text{CH}_3$. Which reagent would show no reaction with this industrial solvent?
May/June 2012
Which compound, when it reacts with hydrogen cyanide, forms a compound containing a chiral centre?
May/June 2012
The compound cis-hex-3-enal is the substance that gives cut grass its distinctive smell. The human nose is especially sensitive to this compound, and can detect $0.25$ parts per billion in air. Which reagents react with cis-hex-3-enal?
May/June 2012
Which carbonyl compound reacts with hydrogen cyanide to produce a product that contains no chiral carbon atom?
May/June 2013
Compound X has an $M_r$ of 72. Its percentage composition by mass is 66.7% carbon, 11.1% hydrogen and 22.2% oxygen. X produces an orange precipitate with 2,4-dinitrophenylhydrazine reagent. X shows no reaction with Fehling’s reagent. What may be concluded from these data?
May/June 2013
The distinctive aroma of burnt sugar is partly due to the compound shown below. $\text{CH}_3-\text{C}(=\text{O})-\text{CHO}$ There are two functional groups in this compound. Which reagent reacts with both functional groups?
May/June 2013
Crotonaldehyde, $\text{CH}_3\text{CH=CHCHO}$, is present in soybean oils.
May/June 2013
$\text{CH}_3\text{CH}_2\text{COCH}_2\text{CH}_3$ reacts with hydrogen cyanide to give an organic product known as a cyanohydrin. Which property is true of the cyanohydrin product?
May/June 2014
Compound X, $\text{C}_4\text{H}_8\text{O}$, gives an orange precipitate when reacted with 2,4-dinitrophenylhydrazine reagent. When compound X is heated under reflux with acidified potassium dichromate(VI) solution, it forms a carboxylic acid. What might compound X be?
May/June 2014
When compound $X$ is heated under reflux with acidified potassium dichromate(VI), it forms a carboxylic acid. Compound $X$ does not react with sodium metal. What might compound $X$ be?
May/June 2014
Hept-4-enal occurs in cow’s milk. $\text{CH}_3\text{CH}_2\text{CH=CHCH}_2\text{CH}_2\text{CHO}$ (hept-4-enal) Which row correctly gives the product obtained when hept-4-enal is reacted with the reducing agent shown?
May/June 2014
With which reagent would compounds P and Q show different observations? P: $\text{HOCH}_2\text{CH(OH)CHO}$ Q: $\text{HOCH}_2\text{COCH}_2\text{OH}$
May/June 2015
The diagram illustrates the structure of compound X. What product is formed when compound X reacts with an excess of $\text{NaBH}_4$?
May/June 2015
The naturally occurring molecule civetone is present in a gland of the African civet cat and has been used in perfumery. Which reagent would not react with civetone?
May/June 2015
Seven structural isomers share the molecular formula $\text{C}_5\text{H}_{10}\text{O}$, and all of them are carbonyl compounds. Of these, four are aldehydes. These four aldehydes, $A$, $B$, $C$ and $D$, have the following features: aldehyde $A$ has a straight-chain structure, whereas $B$, $C$ and $D$ are branched. Aldehyde $B$ is the only one of the four isomers with a chiral centre, so it occurs as a pair of optical isomers. Aldehyde $C$ contains two methyl groups in its structure, while $D$ contains three.
May/June 2015
Which reagent is not suitable for distinguishing ethanal from propanone?
May/June 2016
Which organic compound would fail to produce a yellow precipitate with alkaline aqueous iodine or an orange precipitate with 2,4-dinitrophenylhydrazine reagent?
May/June 2016
When each compound below is heated under reflux with an excess of hot acidified $\text{K}_2\text{Cr}_2\text{O}_7$, how many yield a carboxylic acid? $\text{CH}_3\text{CH}_2\text{CHO}$ $\text{CH}_3\text{COCH}_3$ $\text{CH}_3\text{CH}_2\text{CH}_2\text{OH}$ $\text{CH}_3\text{CH(OH)CH}_3$
May/June 2016
Which compounds produce an orange precipitate when treated with 2,4-dinitrophenylhydrazine reagent?
May/June 2016
You should take both structural isomerism and stereoisomerism into account when answering this question. Each carbonyl compound below is treated with $\text{NaBH}_4$. The product from each reaction is then heated with $\text{Al}_2\text{O}_3$ at $600^\circ\text{C}$, forming either a single product or a mixture of isomers. Which carbonyl compound would give the greatest number of isomers?
May/June 2017
Diols in which both hydroxy groups are attached to the same carbon atom readily lose a molecule of water to form a carbonyl compound. Which compound is hydrolysed to give a product that gives a positive reaction with 2,4-dinitrophenylhydrazine but not with Fehling’s reagent?
May/June 2017
A carbonyl compound X reacts with HCN in the presence of NaCN to produce a compound with $M_r = 85$. Compound X does not react with Fehling’s reagent. Identify X.
May/June 2017
2,2,4-trimethylpentanal is employed in the production of adhesives. With which reagents would 2,2,4-trimethylpentanal react? 1 2,4-dinitrophenylhydrazine reagent 2 Tollens' reagent 3 alkaline aqueous iodine
May/June 2017
The formulae for three compounds are given: $\text{C}_3\text{H}_7\text{CHO}$, $\text{C}_2\text{H}_5\text{COCH}_3$ and $\text{CH}_2\text{CHCH}_2\text{CH}_2\text{OH}$. Of these compounds, only one will decolourise bromine water. Of these compounds, only one will produce a silver mirror with Tollens’ reagent. Which row gives the correct outcomes?
May/June 2017
Substance M is heated under reflux with aqueous sodium hydroxide. One of the products formed in this reaction gives a pale yellow precipitate when it reacts with alkaline aqueous iodine. Which compounds could be substance M?
May/June 2017
Propanal reacts with hydrogen cyanide to produce 2-hydroxybutanenitrile. Sodium cyanide is a suitable catalyst for this reaction. $\text{CH}_3\text{CH}_2\text{CHO} + \text{HCN} \xrightleftharpoons[\text{ }]{\text{NaCN}} \text{CH}_3\text{CH}_2\text{CH(OH)CN}$. Which of the statements below about propanal reacting with hydrogen cyanide are correct?
May/June 2017
Compound Q • has a chiral centre, • produces a positive result with Fehling’s reagent, • produces a positive result with alkaline aqueous iodine. What might compound Q be?
May/June 2018
What mechanism explains the reaction between ethanal, $\text{CH}_3\text{CHO}$, and hydrogen cyanide, $\text{HCN}$, when $\text{NaCN}$ is present?
May/June 2018
The $M_r$ value for compound X is $72$. By mass, X contains $66.7\%$ carbon, $11.1\%$ hydrogen and $22.2\%$ oxygen. X produces an orange precipitate with 2,4-dinitrophenylhydrazine reagent. X shows no reaction with Fehling’s reagent. From this information, what can be inferred?
May/June 2018
Which statement concerning butanone is correct?
May/June 2018
After treatment with $\text{NaBH}_4$, which of these compounds gives a product that contains a chiral carbon atom? 1. $\text{CH}_3\text{CH}_2\text{CH}_2\text{COCH}_3$ 2. $\text{CH}_2\text{CHCOCH}_2\text{CH}_3$ 3. $\text{CH}_3\text{CH}_2\text{COCH}_2\text{CH}_3$
May/June 2018
Propanone and hydrogen cyanide react by the mechanism illustrated. Which of the following statements about this mechanism are correct? 1. $\text{CN}^-$ acts as an electrophile. 2. The reaction is an addition reaction. 3. Heterolytic bond breaking occurs.
May/June 2018
Acrolein is an organic compound whose molecular formula is $\text{C}_3\text{H}_4\text{O}$. It has uses in water treatment and as a herbicide. When acrolein is reacted with $2,4$-dinitrophenylhydrazine, an orange precipitate forms. Acrolein gives a silver mirror with Tollens’ reagent. Which of the following statements are correct? 1. Acrolein reacts with alkaline aqueous iodine to form a yellow precipitate. 2. Acrolein can be reduced to a primary alcohol. 3. Acrolein decolourises bromine water.
May/June 2018
$W$ has the formula $\text{CH}_3\text{COCH}_2\text{CH}_3$.
May/June 2018
Compound X is reacted in turn with two reagents, giving compound Z. Initially, X is treated with a mild oxidising agent to yield Y. Y is then reacted with $\text{NaBH}_4$ to give Z. What could Z be?
May/June 2019
Which reagent can be used to tell propanone apart from ethanol?
May/June 2019
Which reagent could be used to tell ethanal and propanal apart?
May/June 2019
When compound Q is treated with $2,4$-dinitrophenylhydrazine, a precipitate forms. Compound Q does not form a precipitate on warming with Fehling’s solution. What might compound Q be?
May/June 2019
Only structural isomerism is to be taken into account for this question. A collection of isomeric compounds, each with molecular formula $\text{C}_5\text{H}_{10}\text{O}$, all undergo nucleophilic addition with excess HCN in a $1:1$ ratio. How many isomeric compounds are there in the collection?
May/June 2019
Ethanal undergoes reaction with a mixture of HCN and NaCN to form 2-hydroxypropanenitrile, $\text{CH}_3\text{CH(OH)CN}$. The mechanism for this reaction is nucleophilic addition.
May/June 2019
With the apparatus arranged as shown, an orange precipitate is produced in test-tube Z. Compound Q is heated with acidified potassium dichromate(VI), and the vapour then travels into test-tube Z, which contains 2,4-dinitrophenylhydrazine reagent. What might compound Q be?
May/June 2020
Compound X has the structure shown. Which of the following statements about compound X are correct? 1. X will decolourise cold, acidified $\text{KMnO}_4\text{(aq)}$. 2. X produces an orange precipitate with $\text{2,4-DNPH}$ reagent. 3. X does not react with Tollens’ reagent.
May/June 2020
The structure of Compound X is shown. What kind of carbonyl group is present, and how many chiral centres does one molecule of X contain?
May/June 2020
The reaction sequence illustrates how ethene, $\text{C}_2\text{H}_4$, may be changed into other organic molecules.
May/June 2020
Which statement is correct about the reaction between carbonyl compounds and HCN?
May/June 2021
By using a test with alkaline aqueous iodine, which of the following pairs of compounds can be told apart? 1 butanal and butanone 2 pentan-$2$-one and pentan-$3$-ol 3 propanone and propan-$2$-ol
May/June 2021
The skeletal formulae of three compounds, R, S and T, are shown. Which of these compounds would produce a positive result with 2,4-dinitrophenylhydrazine reagent?
May/June 2021
The diagram illustrates the structure of a compound produced when HCN reacts with a carbonyl compound, X. Name the mechanism of this reaction and the functional group present in X?
May/June 2021
Three compounds, X, Y and Z, are shown here. $X$: $\text{C}_2\text{H}_5\text{COCH}_3$, $Y$: $\text{C}_2\text{H}_5\text{CHO}$, $Z$: $\text{CH}_3\text{CO}_2\text{H}$. Which of the following statements about X, Y and Z are correct?
May/June 2021
Which compound reacts with $\text{LiAlH}_4$ to produce two optical isomers?
May/June 2022
When a carbonyl compound, $X$, is treated with HCN in the presence of NaCN, a product with $M_r = 85$ is formed. $X$ gives no reaction with Fehling’s reagent. Which compound is $X$?
May/June 2022
Which compound gives a precipitate on mixing with 2,4-DNPH reagent and also gives a precipitate on mixing with Fehling’s reagent?
May/June 2022
Only structural isomerism should be taken into account when answering this question. A number of compounds with molecular formula $\text{C}_4\text{H}_8\text{O}_2$ contain one carbonyl group and one OH group. How many of these compounds form yellow crystals with alkaline $\text{I}_2(aq)$ at room temperature?
May/June 2022
Which reaction follows a nucleophilic addition mechanism and produces a good yield of product under the conditions given?
May/June 2022
A carbonyl compound has the structural formula $\text{CH}_3\text{COCHO}$. Which row shows the correct observations when this compound is reacted with the reagents given?
May/June 2022
Which reagent: • is able to confirm that an organic compound contains a carbonyl group • cannot tell aldehydes from ketones?
May/June 2023
Which compound gives a positive result with alkaline aqueous iodine and does not display optical isomerism?
May/June 2023
Compound G forms a pale yellow precipitate with alkaline $\text{I}_2\text{(aq)}$. Which compound could G be?
May/June 2023
The reaction pathway between ethanal and hydrogen cyanide begins with the step illustrated below. Which is the correct structure of the intermediate ion produced, and what happens next in this mechanism?
May/June 2023
Which compound gives a reaction with 2,4-dinitrophenylhydrazine reagent but shows no reaction with Tollens’ reagent?
May/June 2023