Carboxylic acids and derivatives

6(a) M1: ethanoic acid > butanoic acid > water > ethanol 4 M2: a reason given in terms of an electron donating or an electron withdrawing group for one of: strengthening of O–H bond OR weakening of O–H bond OR stability of anion Two out of the three alternatives M3, M4 and M5: M3: ethanol: positive inductive effect / electron donating effect of ethyl / alkyl / R group M4: butanoic acid: positive inductive effect / electron donating effect of propyl / alkyl / R group M5: (either ethanoic or butanoic) acid: negative inductive effect of either C=O or carbonyl OR negative charge delocalised over COO– 6(b)(i) 3 reagents and conditions observed change Tollen’s reagent, warm silver mirror test 1 OR Fehling’s solution, warm (brick) red ppt / solid test 2 acidified MnO –, warm decolourises OR bubbles 4 M1 / M2: reagents and conditions × 2 M3: observations both correct © UCLES 2021 Page 12 of 17 6(b)(ii) 2 number of peaks in number of peaks in compound proton NMR carbon-13 NMR HCO H 2 1 2 HO CCO H 1 1 2 2 HO CCH CH CO H 2 2 2 2 2 2 one mark for three, four or five correct two marks for six correct 6(b)(iii) OH peak disappears AND proton / H exchanges with deuterium 1 6(c)(i) G = HOCH CH CH CH OH 2 2 2 2 2 H = NCCH CH CH CH CN 2 2 2 2 6(c)(ii) M1: step 1 NaOH(aq) + heat 4 M2: step 2 acidified KMnO + heat / acidified K Cr O + heat 4 2 2 7 M3: step 3 CN– / KCN / NaCN + heat M4: step 4 LiAlH ALLOW Na in ethanol or H + Ni / Pd / Pt 4 2 6(d) 2 M1: correct displayed amide linkage M2: the rest of the repeat unit correct including trailing bonds © UCLES 2021 Page 13 of 17

8(a) M1: 3 acyl chlorides > alkyl chlorides > aryl chlorides fastest slowest M2 / 3: Any two from: • acyl chlorides carbon in C-Cl bond is more electron deficient since it is also attached to an oxygen atom OR C-Cl bond is weakest / weakened in acyl chlorides since it is also attached to an oxygen atom / two electronegative atoms • aryl chlorides (no hydrolysis) C-Cl bond is part of delocalised system / partially double bond character (so C-Cl bond is stronger) OR lone pair / p-orbital on Cl delocalises with π ring (so C-Cl bond is stronger) • alkyl chlorides C-Cl bond strengthened by electron donating effect / positive inductive effect of alkyl / R group (as compared to acyl chlorides) OR carbon atom has a smaller δ+ and the C-Cl bond is stronger (than the C-Cl bond in COCl) due to (the carbon) being only attached to one electronegative atom 8(b) 3 ALLOW amine salt for the third structure – mono or di ion 8(c)(i) 1 © UCLES 2021 Page 15 of 16 8(c)(ii) 3 chemical splitting pattern number of 1H atoms environment of proton shift (δ) (words required) responsible for the peak 0.95 alkane / CH doublet 6 3 1.90 alkane / CH multiplet 1 ALLOW alkyne 2.20 R / alkyl / CH next to doublet 2 2 C=O / COOH mark as • •  • •  • •  © UCLES 2021 Page 16 of 16

6(a) M1: ethanoic acid > butanoic acid > water > ethanol 4 M2: a reason given in terms of an electron donating or an electron withdrawing group for one of: strengthening of O–H bond OR weakening of O–H bond OR stability of anion Two out of the three alternatives M3, M4 and M5: M3: ethanol: positive inductive effect / electron donating effect of ethyl / alkyl / R group M4: butanoic acid: positive inductive effect / electron donating effect of propyl / alkyl / R group M5: (either ethanoic or butanoic) acid: negative inductive effect of either C=O or carbonyl OR negative charge delocalised over COO– 6(b)(i) 3 reagents and conditions observed change Tollen’s reagent, warm silver mirror test 1 OR Fehling’s solution, warm (brick) red ppt / solid test 2 acidified MnO –, warm decolourises OR bubbles 4 M1 / M2: reagents and conditions × 2 M3: observations both correct © UCLES 2021 Page 12 of 17 6(b)(ii) 2 number of peaks in number of peaks in compound proton NMR carbon-13 NMR HCO H 2 1 2 HO CCO H 1 1 2 2 HO CCH CH CO H 2 2 2 2 2 2 one mark for three, four or five correct two marks for six correct 6(b)(iii) OH peak disappears AND proton / H exchanges with deuterium 1 6(c)(i) G = HOCH CH CH CH OH 2 2 2 2 2 H = NCCH CH CH CH CN 2 2 2 2 6(c)(ii) M1: step 1 NaOH(aq) + heat 4 M2: step 2 acidified KMnO + heat / acidified K Cr O + heat 4 2 2 7 M3: step 3 CN– / KCN / NaCN + heat M4: step 4 LiAlH ALLOW Na in ethanol or H + Ni / Pd / Pt 4 2 6(d) 2 M1: correct displayed amide linkage M2: the rest of the repeat unit correct including trailing bonds © UCLES 2021 Page 13 of 17

5(a) M1 benzoic acid > phenol > phenylmethanol 3 M2 / M3 Any two of:  in benzoic acid negative inductive effect of C=O AND O-H bond is weakened OR due to delocalisation of minus charge by C=O / 2O carboxylate ion is stabilised  in phenol lone pair on oxygen is delocalised into the ring AND O-H bond is weakened  in phenyl methanol positive inductive effect of CH group AND O-H bond is strengthened 2 5(b) 3 benzoic acid phenylmethanol phenol Na(s)    NaOH(aq)    Na CO (aq)    2 3 Three correct for one mark, six correct for two marks, nine correct for three marks © UCLES 2022 Page 10 of 15 5(c)(i) POCl and HCl AND SO and HCl 1 3 2 5(c)(ii) all the by-products / SO and HCl are gaseous OR no liquid by-products formed 1 2 5(d)(i) 4 On the left-hand side:  lone pair on O  correct arrow from O to C (of C=O)  dipole on C=O  correct arrow on C=O M1 / M2 Two correct for one mark, four correct for two marks On the right-hand side: M3 correct intermediate M4 arrow from lone pair on O– to C-O bond AND arrow from C-Cl to Cl 5(d)(ii) addition-elimination 1 © UCLES 2022 Page 11 of 15 5(e)(i) 2 OR 5(e)(ii) hydrolysis OR heating in dilute acid / alkali 1 Question Answer Marks

5(a) M1 benzoic acid > phenol > phenylmethanol 3 M2 / M3 Any two of:  in benzoic acid negative inductive effect of C=O AND O-H bond is weakened OR due to delocalisation of minus charge by C=O / 2O carboxylate ion is stabilised  in phenol lone pair on oxygen is delocalised into the ring AND O-H bond is weakened  in phenyl methanol positive inductive effect of CH group AND O-H bond is strengthened 2 5(b) 3 benzoic acid phenylmethanol phenol Na(s)    NaOH(aq)    Na CO (aq)    2 3 Three correct for one mark, six correct for two marks, nine correct for three marks © UCLES 2022 Page 10 of 15 5(c)(i) POCl and HCl AND SO and HCl 1 3 2 5(c)(ii) all the by-products / SO and HCl are gaseous OR no liquid by-products formed 1 2 5(d)(i) 4 On the left-hand side:  lone pair on O  correct arrow from O to C (of C=O)  dipole on C=O  correct arrow on C=O M1 / M2 Two correct for one mark, four correct for two marks On the right-hand side: M3 correct intermediate M4 arrow from lone pair on O– to C-O bond AND arrow from C-Cl to Cl 5(d)(ii) addition-elimination 1 © UCLES 2022 Page 11 of 15 5(e)(i) 2 OR 5(e)(ii) hydrolysis OR heating in dilute acid / alkali 1 Question Answer Marks

6(a)(i) 5 / five 1 6(a)(ii) M1 benefit: 2 higher biological efficiency / activity (of the drug) OR less side effects OR smaller dose required (as drug more potent) M2 disadvantage: the need to separate (a racemic mixture into a single stereoisomer) OR lower yield (of biologically active molecule/product) OR need a chiral catalyst / enzyme (in the synthesis so expensive) 6(b)(i) carboxylic acid/carboxyl, ester, amide, amine 2 Any two [1], all four [2] © UCLES 2023 Page 14 of 19 6(b)(ii) 3 3  [1] for each structure Question Answer Marks

9(a)(i) 1 [1] 9(a)(ii) hot (alkaline) KMnO / MnO – [1] 2 4 4 SOCl OR PCl OR PCl + heat[1] 2 5 3 9(a)(iii) oxidation [1] 2 (nucleophilic) substitution © UCLES 2023 Page 16 of 18 9(b)(i) 10 and HCl The red numbers refer to points 1 to 10 in the verbal MS that follows. box one: 4 • 1 dipole on C=O • 2 curly arrow from O of phenol to C of acyl chloride • 3 curly arrow from bond of C=O to O of acyl chloride box two: • 4 curly arrow from O-H bond to what was O of phenol • 5 curly arrow from C-Cl bond to what was Cl of acyl chloride • 6 curly arrow from O to reform C=O • 7 + charge on what was O of phenol • 8 – charge on what was O of acyl chloride • 9 curly arrow start close to LP for bullet 3 OR 6 (from LP on O) box three: • 10 HCl / H+Cl – any two [1] any five [2] any eight [3] all ten [4] 9(b)(ii) (nucleophilic) addition-elimination [1] 1 © UCLES 2023 Page 17 of 18 9(c) chlorobenzene, chloroethane, benzoyl chloride [1] u / c 3 explanation linked to their order • correct link to: strengthening (ArCl / RCl) C-Cl bond OR weakening (RCOCl) C-Cl bond OR C-Cl bond has partially double bond character (ArCl) OR C-Cl is more difficult to break (linked correctly) chlorobenzene: • lone pair / p-orbital on Cl overlaps / delocalised / incorporated with ring benzoyl chloride: • C of C-Cl has most electron deficient OR has an electronegative oxygen atom / two electronegative atoms / electron withdrawing C=O group chloroethane • electron donating effect / positive inductive effect of alkyl / R group any two [1] any three [2] © UCLES 2023 Page 18 of 18

9(a)(i) 1 [1] 9(a)(ii) hot (alkaline) KMnO / MnO – [1] 2 4 4 SOCl OR PCl OR PCl + heat[1] 2 5 3 9(a)(iii) oxidation [1] 2 (nucleophilic) substitution © UCLES 2023 Page 16 of 18 9(b)(i) 10 and HCl The red numbers refer to points 1 to 10 in the verbal MS that follows. box one: 4 • 1 dipole on C=O • 2 curly arrow from O of phenol to C of acyl chloride • 3 curly arrow from bond of C=O to O of acyl chloride box two: • 4 curly arrow from O-H bond to what was O of phenol • 5 curly arrow from C-Cl bond to what was Cl of acyl chloride • 6 curly arrow from O to reform C=O • 7 + charge on what was O of phenol • 8 – charge on what was O of acyl chloride • 9 curly arrow start close to LP for bullet 3 OR 6 (from LP on O) box three: • 10 HCl / H+Cl – any two [1] any five [2] any eight [3] all ten [4] 9(b)(ii) (nucleophilic) addition-elimination [1] 1 © UCLES 2023 Page 17 of 18 9(c) chlorobenzene, chloroethane, benzoyl chloride [1] u / c 3 explanation linked to their order • correct link to: strengthening (ArCl / RCl) C-Cl bond OR weakening (RCOCl) C-Cl bond OR C-Cl bond has partially double bond character (ArCl) OR C-Cl is more difficult to break (linked correctly) chlorobenzene: • lone pair / p-orbital on Cl overlaps / delocalised / incorporated with ring benzoyl chloride: • C of C-Cl has most electron deficient OR has an electronegative oxygen atom / two electronegative atoms / electron withdrawing C=O group chloroethane • electron donating effect / positive inductive effect of alkyl / R group any two [1] any three [2] © UCLES 2023 Page 18 of 18

6(a)(i) ClOCCOCl [1] 1 6(a)(ii) PCl / PCl [1] 1 3 5 6(b) oxygen [1] 2 acidified KMnO [1] 4 6(c) C=O are electron withdrawing / electronegative [1] 2 weakens O–H bond OR stabilises anion [1] 6(d)(i) 1 [1] 6(d)(ii) step 1: CH Cl + AlCl [1] 2 3 3 step 2: hot alkaline KMnO [1] 4 © Cambridge University Press & Assessment 2024 Page 9 of 12 6(d)(iii) 2 correctly displayed ester linkage [1] rest of structure [1] 6(d)(iv) condensation AND ester [1] 1 Question Answer Marks

10(a) 1 10(b) M1: reagent 1:Fehling’s OR Tollens’ reagent 4 M2: acidified MnO – 4 observation when treated observation when treated with reagent 1 with reagent 2 propanoic acid no change no change methanoic acid red ppt OR silver mirror colourless ethanedioic acid no change colourless M3 / M4: One completely correct column [1] both completely correct columns [2] 10(c) M1: chlorine atoms are electron withdrawing / electronegative 2 M2: weakening O–H bond OR stabilising conjugate base © Cambridge University Press & Assessment 2025 Page 16 of 16

10(a) 1 10(b) M1: reagent 1:Fehling’s OR Tollens’ reagent 4 M2: acidified MnO – 4 observation when treated observation when treated with reagent 1 with reagent 2 propanoic acid no change no change methanoic acid red ppt OR silver mirror colourless ethanedioic acid no change colourless M3 / M4: One completely correct column [1] both completely correct columns [2] 10(c) M1: chlorine atoms are electron withdrawing / electronegative 2 M2: weakening O–H bond OR stabilising conjugate base © Cambridge University Press & Assessment 2025 Page 16 of 16

7(a) M1: benzoic acid > phenol > ethanol 3 M2 / M3: any two [1] any three [2] • correct link of acidity once AND weakens O—H / OH bond / hydroxyl bond / -O-H OR H+ more easily lost / (carboxylate) anion stabilised u / c • (benzoic acid) due to negative inductive effect / electron withdrawing effect AND of C=O / COOH / carboxyl • (phenol) as lone pair / p-orbital (electrons) on oxygen (on phenol) / AND overlap / delocalised into the ring / π-system • (ethanol) alkyl / ethyl / R group AND is electron donating / positive inductive effect 7(b) 2 Each correct structure = [1] 7(c)(i) ethyl propanoate 1 © Cambridge University Press & Assessment 2025 Page 15 of 17 7(c)(ii) 4 M1 / M2: any two [1] all four [2] • lone pair on O • correct arrow from (lone pair) O to C (of C=O) • dipole on C=O • correct arrow on C=O M3: correct intermediate M4: arrow from lone pair or charge on O– to C-O bond AND arrow from C-Cl to Cl 7(c)(iii) (nucleophilic) addition – elimination 1 Question Answer Marks

7(a) M1: ClCH 2 COOH BrCH 2 COOH CH 3 COOH CH 3 CH 2 OH 4 most acidic least acidic M2: electron withdrawing groups / electronegative groups / negative inductive effect AND weakens O–H bond / more stable anion OR electron donating groups / positive inductive effect AND strengthens O-H bond / less stable anion M3 M4: • chlorine is more electron-withdrawing / electronegative than bromine (related to XCH COOH) 2 • electron withdrawing of C=O / negative inductive effect of C=O (related to COOH) • positive inductive effect / electron donating of alkyl / ethyl / R group (related to ROH) any two [1], all three [2] 7(b) M1: 2 M2: CO 2 © Cambridge University Press & Assessment 2025 Page 14 of 19 7(c)(i) 2 M1: correct displayed amide bond with C=O, (C H )−N and (C–)C=O 6 5 M2: rest of the structure correct with continuation bonds 7(c)(ii) 1 7(d)(i) 2 M1: M2: © Cambridge University Press & Assessment 2025 Page 15 of 19 7(d)(ii) HNO (and HCl) AND ⩽10 °C 1 2 OR NaNO AND HCl AND ⩽10 °C 2 Question Answer Marks

8(a)(i) NO group directs to 3 (and 5) / meta position AND due to being an electron-withdrawing / electronegative group 1 2 8(a)(ii) HNO + H SO → NO + + HSO – + H O 1 3 2 4 2 4 2 OR HNO + 2H SO → NO + + 2HSO – + H O+ 3 2 4 2 4 3 8(b)(i) 1 8(b)(ii) M1: (reaction 1) ethanoyl chloride / CH 3 COCl AND AlCl3 2 M2: (reaction 2) 2-bromopropane / (CH ) CHBr AND FeBr 3 2 3 8(c) M1: 3 with C H Br no change / no precipitate AND 6 5 with C H CH Br cream precipitate 6 5 2 in C H Br 6 5 M2: lone pair / p-orbital on Br delocalised / overlaps with ring /  system M3: C–Br bond stronger / has partially double bond character © Cambridge University Press & Assessment 2025 Page 16 of 19 8(d)(i) (nucleophilic) addition–elimination 1 8(d)(ii) 4 M1 M2: • lone pair on O • curly arrow from (lone pair) O (in H O) to C (of C=O) 2 • correct dipole on C=O • curly arrow from the C=O bond to O atom any two [1], all four [2] M3: correct intermediate M4: curly arrow from (lone pair on) O(–) to C–O bond AND curly arrow from C–Br to Br Question Answer Marks

7(a) M1: ClCH 2 COOH BrCH 2 COOH CH 3 COOH CH 3 CH 2 OH 4 most acidic least acidic M2: electron withdrawing groups / electronegative groups / negative inductive effect AND weakens O–H bond / more stable anion OR electron donating groups / positive inductive effect AND strengthens O-H bond / less stable anion M3 M4: • chlorine is more electron-withdrawing / electronegative than bromine (related to XCH COOH) 2 • electron withdrawing of C=O / negative inductive effect of C=O (related to COOH) • positive inductive effect / electron donating of alkyl / ethyl / R group (related to ROH) any two [1], all three [2] 7(b) M1: 2 M2: CO 2 © Cambridge University Press & Assessment 2025 Page 14 of 19 7(c)(i) 2 M1: correct displayed amide bond with C=O, (C H )−N and (C–)C=O 6 5 M2: rest of the structure correct with continuation bonds 7(c)(ii) 1 7(d)(i) 2 M1: M2: © Cambridge University Press & Assessment 2025 Page 15 of 19 7(d)(ii) HNO (and HCl) AND ⩽10 °C 1 2 OR NaNO AND HCl AND ⩽10 °C 2 Question Answer Marks

8(a)(i) NO group directs to 3 (and 5) / meta position AND due to being an electron-withdrawing / electronegative group 1 2 8(a)(ii) HNO + H SO → NO + + HSO – + H O 1 3 2 4 2 4 2 OR HNO + 2H SO → NO + + 2HSO – + H O+ 3 2 4 2 4 3 8(b)(i) 1 8(b)(ii) M1: (reaction 1) ethanoyl chloride / CH 3 COCl AND AlCl3 2 M2: (reaction 2) 2-bromopropane / (CH ) CHBr AND FeBr 3 2 3 8(c) M1: 3 with C H Br no change / no precipitate AND 6 5 with C H CH Br cream precipitate 6 5 2 in C H Br 6 5 M2: lone pair / p-orbital on Br delocalised / overlaps with ring /  system M3: C–Br bond stronger / has partially double bond character © Cambridge University Press & Assessment 2025 Page 16 of 19 8(d)(i) (nucleophilic) addition–elimination 1 8(d)(ii) 4 M1 M2: • lone pair on O • curly arrow from (lone pair) O (in H O) to C (of C=O) 2 • correct dipole on C=O • curly arrow from the C=O bond to O atom any two [1], all four [2] M3: correct intermediate M4: curly arrow from (lone pair on) O(–) to C–O bond AND curly arrow from C–Br to Br Question Answer Marks

8(a) • chlorobenzene is less reactive than ethanoyl chloride 2 • p orbital / lone pair on Cl / –Cl will overlap / delocalise into the ring OR C of COCl has most electron deficient OR has an electronegative oxygen atom / two electronegative atoms / electron withdrawing C=O group • due to partial double C–Cl bond OR C–Cl bond strengthened (more) / stronger bond between Cl and benzene / ring OR C–Cl weakened in ROCl any two [1], all three [2] 8(b)(i) • nitrile 2 • amide • ketone / carbonyl • ester any two [1], all four [2] 8(b)(ii) 8 / eight 1 8(b)(iii) no need to separate optical isomers 1 © Cambridge University Press & Assessment 2025 Page 15 of 16 8(c) 3 M1: amide bond hydrolysed and COO– and NH formed 2 M2: nitrile bond hydrolysed and COO– formed M3: ester bond hydrolysed and COO– and OH formed 8(d)(i) percentage = 100  28 / (28 + 58 + 13 + 42) = 19.9(%) min 2sf 1 8(d)(ii) D is attracted more strongly to the stationary phase / forms stronger intermolecular forces with the stationary phase 1 © Cambridge University Press & Assessment 2025 Page 16 of 16

4(a)(i) two separate half-life readings quoted t ≅ 6000 (s) 250 2 ½ same / constant half-life (∴ first order with respect to [ester]) 4(a)(ii) tangent seen at t = 0 AND initial rate (from gradient of tangent) ≅ 0.24 / 8750 = 2.74  10–5 (mol dm–3 s–1) min 2sf 1 4(a)(iii) rate = k [CH COOCH ] [H+] 2 3 3 mol–1 dm3 s–1 4(b)(i) • reaction 6 / CH COCl goes to completion / non-reversible 2 3 • reaction 7 / CH COOH is an equilibrium (reaction) / reversible 3 • reaction 6 has a gas formed AND has a greater S / entropy is increased (so more feasible) any two [2] 4(b)(ii) 4 M1: correct arrow from lone pair on O (in CH OH) to C (of C=O) 3 M2: correct dipole on C=O AND correct arrow from the C=O bond to O atom M3: correct intermediate (both charges present) M4: arrow from (lone pair on) O(–) to C–O bond AND arrow from C-Cl bond to Cl © Cambridge University Press & Assessment 2026 Page 14 of 18 4(c) M1: chlorobenzene < chloroethane < ethanoyl chloride 3 M2 & M3: Any two from: (acyl chlorides easier than alkyl chlorides) • has two electronegative atom groups/an extra electronegative atom / an electronegative oxygen / electron withdrawing C=O AND so C (of C=O) highly / more electron deficient / C-Cl bond weak(est) (aryl chlorides hardest) • LP / lone pair / p-orbital on Cl/chlorine AND overlaps / delocalised with ring /  system AND (C-Cl) bond is strengthened / has partial double bond character (alkyl chlorides easier than aryl chlorides) • carbon is bonded to an electronegative atom / Cl / not bonded to electronegative O AND so has less electron deficient carbon OR • C-Cl bond strengthened AND by positive inductive effect of alkyl / R group Question Answer Marks