A-LevelChemistryCarboxylic acids and derivatives9701/21 · May/June 2025 · Q512 Marks

Compound A contains the elements carbon, hydrogen and oxygen only. When A is heated with H2SO4(aq), compounds B and C are produced, as shown in Fig. 5.1. [Figure 5.1]

(a)Draw the structure of A.[2]
(b)Name the type of reaction that occurs when A is heated with H2SO4(aq).[1]
(c)(i)Complete the equation to describe the reaction between B and an excess of aqueous Na2CO3. .HOOCCH2COOH + .Na2CO3[1]
(c)(ii)Suggest why C does not react with aqueous Na2CO3 in a similar type of reaction to B.[1]
(d)(i)Identify the reagents and conditions required in steps 1 and 2. step 1 step 2[2]
(d)(ii)Identify the type of reaction that HOCH2CH2CH2OH undergoes in step 2.[1]
(e)(i)Identify the formula of the reducing agent R.[1]
(e)(ii)Complete the equation to describe the reaction of B with an excess of R. Use [H] to represent one atom of hydrogen from R. HOOCCH2COOH + ......[H][2]
(e)(iii)Name organic compound E.[1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2025). The mark or mark type is shown in brackets.

[2] M1 two ester links; M2 rest of structure correct (CH3CH2OOCCH2COOCH2CH3)
[1] (acid) hydrolysis
[1] HOOCCH2COOH + Na2CO3 → NaOOCCH2COONa + CO2 + H2O
[1] C is not as strong an acid as B
[2] M1 step 1: NaOH(aq) AND heat; M2 step 2: acidified AND potassium dichromate(VI) AND heat under reflux
[1] oxidation
[1] LiAlH4
[2] M1 correct unambiguous organic product (HOCH2CH2CH2OH); M2 correct balanced equation (HOOCCH2COOH + 8[H] → HOCH2CH2CH2OH + 2H2O)
[1] 1,3-dichloropropane

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.