Carbonyl compounds: past paper questions

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• Question 33May/June 2026, paper 11Multiple choice1 markHas a diagram

  When an acidified aqueous solution of potassium cyanide is added to propanone, an addition reaction takes place. Which structure shows the intermediate formed during this reaction?

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• Question 33Oct/Nov 2025, paper 11Multiple choice1 markHas a diagram

  The balanced equation for the reaction of X with an excess of acidified ${\text{K}}_2{\text{Cr}}_2{\text{O}}_7$ is shown. $$\text{X}+3[\text{O}]\to \text{Y}+{\text{H}}_2\text{O}$$ Compound Y is the only organic product of the reaction. Which compound is X?

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• Question 34Oct/Nov 2024, paper 11Multiple choice1 mark

  Compound Y reacts with alkaline ${\text{I}}_2(\text{aq})$. When the products of this reaction are acidified, a dicarboxylic acid is produced. The formula of the dicarboxylic acid is $\text{HOOC–R–COOH}$ where R consists of one or more ${\text{CH}}_2$ groups.

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• Question 36Oct/Nov 2023, paper 11Multiple choice1 markHas a diagram

  Which compound will produce a yellow-orange precipitate when added to 2,4-dinitrophenylhydrazine?

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• Question 34May/June 2026, paper 11Multiple choice1 markHas a diagram

  The structural formulas of four isomers of ${\text{C}}_5{\text{H}}_{10}\text{O}$ are listed.

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• Question 36Oct/Nov 2025, paper 11Multiple choice1 mark

  Compound Q reacts when heated with $\text{HCN}$ in the presence of a catalyst to produce compound R. Molecules of compound R each contain four carbon atoms. What is compound Q?

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• Question 36Oct/Nov 2024, paper 11Multiple choice1 mark

  Which compound, on reaction with hydrogen cyanide, produces a compound with a chiral centre?

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• Question 37Oct/Nov 2023, paper 11Multiple choice1 markHas a diagram

  Ethanal, ${\mathrm{C}\mathrm{H}}_3\mathrm{C}\mathrm{H}\mathrm{O}$, undergoes an addition reaction with $\mathrm{H}\mathrm{C}\mathrm{N}$ in the presence of ${\mathrm{C}\mathrm{N}}^{-}$ ions. Which row identifies the type of reaction and the name of the product formed?

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• Question 27May/June 2026, paper 12Multiple choice1 mark

  Structural isomerism and stereoisomerism should be considered when answering this question. Several isomers with molecular formula ${\text{C}}_5{\text{H}}_{10}\text{O}$ give an orange precipitate with 2,4-DNPH reagent.

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• Question 38Oct/Nov 2025, paper 11Multiple choice1 mark

  Seven aldehydes and ketones ● contain only one oxygen atom per molecule ● have four or fewer carbon atoms in their structures. Alkaline ${\text{I}}_2(\text{aq})$ is added to each of these carbonyl compounds separately.

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• Question 37Oct/Nov 2024, paper 11Multiple choice1 markHas a diagram

  The diagram shows three reactions of ethanal. In each case, an excess of ethanal is used. Observations are made after each of the three reactions.

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• Question 31Oct/Nov 2023, paper 12Multiple choice1 markHas a diagram

  The formulae of three compounds are shown. $${\text{C}}_3{\text{H}}_7\text{CHO}{\text{C}}_2{\text{H}}_5{\text{COCH}}_3{\text{CH}}_2{\text{CHCH}}_2{\text{CH}}_2\text{OH}$$ Only one of these compounds will decolourise bromine water.

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• Question 31May/June 2026, paper 12Multiple choice1 mark

  Which reaction has ethanol as the major organic product?

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• Question 39Oct/Nov 2025, paper 11Multiple choice1 markHas a diagram

  Some properties of compound X are listed. ● $1.0\text{ mol}$ X reacts with exactly $8.5\text{ mol}$ oxygen when completely combusted. ● X does not react when heated with acidified ${\text{KMnO}}_4$.

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• Question 34Oct/Nov 2024, paper 12Multiple choice1 mark

  Compound X: ● does not react with Tollens' reagent ● forms a yellow precipitate with alkaline ${\mathrm{I}}_2(\mathrm{a}\mathrm{q})$ ● does not react with sodium. What could be the identity of X?

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• Question 34Oct/Nov 2023, paper 12Multiple choice1 mark

  Which alcohol reacts with alkaline ${\text{I}}_2\text{(aq)}$ to produce ethanoate ions?

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• Question 33May/June 2026, paper 12Multiple choice1 mark

  Which pair of compounds can be distinguished by adding alkaline ${\text{I}}_2\text{(aq)}$?

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• Question 25Oct/Nov 2025, paper 12Multiple choice1 mark

  Two statements about a molecule of methanal are given. 1 It is planar. 2 It contains three $\sigma$ bonds.

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• Question 35Oct/Nov 2024, paper 12Multiple choice1 mark

  Which compound can undergo nucleophilic addition?

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• Question 35Oct/Nov 2023, paper 12Multiple choice1 markHas a diagram

  Heating compound X, ${\text{C}}_7{\text{H}}_{14}{\text{O}}_2$, under reflux with an excess of acidified potassium dichromate(VI) produces compound Y. Compound Y produces hydrogen gas with sodium metal and forms orange crystals with 2,4-DNPH reagent. What could X be?

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• Question 38May/June 2026, paper 12Multiple choice1 mark

  Compound X, ${\text{CH}}_3{\text{CH(OH)CH(CHO)CH}}_3$, is heated under reflux with an excess of acidified ${\text{K}}_2{\text{Cr}}_2{\text{O}}_7$ to form compound Y. Both X and Y are separately warmed with Fehling’s reagent and the observations noted. What are the observations?

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• Question 33Oct/Nov 2025, paper 12Multiple choice1 mark

  ${\text{HOCH}}_2\text{CHO}$ is heated under reflux with an excess of acidified ${\text{K}}_2{\text{Cr}}_2{\text{O}}_7$ until there is no further reaction. What is the final product of this reaction?

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• Question 34Oct/Nov 2024, paper 13Multiple choice1 mark

  Compound Y reacts with alkaline ${\mathrm{I}}_2(\mathrm{a}\mathrm{q})$. When the products of this reaction are acidified, a dicarboxylic acid is produced. The formula of the dicarboxylic acid is $\mathrm{H}\mathrm{O}\mathrm{O}\mathrm{C}-\mathrm{R}-\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{H}$ where R consists of one or more ${\mathrm{C}\mathrm{H}}_2$ groups.

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• Question 36Oct/Nov 2023, paper 12Multiple choice1 mark

  Which reaction takes place by a nucleophilic addition mechanism?

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• Question 31May/June 2026, paper 13Multiple choice1 mark

  Compound Q with molecular formula ${\text{C}}_4{\text{H}}_{10}\text{O}$ gives compound R with molecular formula ${\text{C}}_4{\text{H}}_8\text{O}$ upon oxidation. R gives a yellow precipitate with alkaline ${\text{I}}_2\text{(aq)}$. What is Q?

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• Question 34Oct/Nov 2025, paper 12Multiple choice1 markHas a diagram

  An organometallic lithium compound, $\text{RLi}$, contains the nucleophile ${\text{R}}^{-}$. ${\text{CH}}_3{\text{CH}}_2\text{Li}$ reacts with pentan-2-one. The mechanism is nucleophilic addition.

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• Question 30Oct/Nov 2023, paper 13Multiple choice1 markHas a diagram

  $\beta$-carotene is responsible for the orange colour of carrots. $\beta$-carotene is oxidised by hot, concentrated, acidified ${\text{KMnO}}_4$. When an individual molecule of $\beta$-carotene is oxidised in this way, many product molecules are formed.

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• Question 33May/June 2026, paper 13Multiple choice1 mark

  Two reactions are described. 1 1-bromopropane with ammonia 2 propanal with hydrogen cyanide Which of these reactions has a nucleophilic mechanism?

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• Question 35Oct/Nov 2025, paper 12Multiple choice1 markHas a diagram

  The structure of a naturally occurring compound, Q, is shown. Compound Q is heated under reflux with an excess of acidified ${\text{KMnO}}_4$. Organic product R is formed.

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• Question 37Oct/Nov 2024, paper 13Multiple choice1 markHas a diagram

  The diagram shows three reactions of ethanal. In each case, an excess of ethanal is used.

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