Hydrocarbons

6(a) 4 correct isomers and correct assignment to peaks: mark as •  •  •  •  6(b)(i) RCl + AlCl  R+ + AlCl – 1 3 4 OR Cl(CH ) COOH + AlCl  +(CH ) COOH + AlCl – 2 3 3 2 3 4 6(b)(ii) 2 © UCLES 2021 Page 12 of 16 6(b)(iii) SOCl OR PCl 1 2 5 ALLOW PCl AND heat 3 6(b)(iv) 3 M1: arrow to R+ OR arrow to positive carbon of +(CH ) COOH 2 3 M2: correct structure of intermediate M3: arrow from C-H bond into the ring AND H+ Question Answer Marks

7(a) C H O [1] 1 4 3 2 7(b) 2 benzene-1,3-dicarboxylic acid 5 [1] benzene-1,4-dicarboxylic acid 3 [1] 7(c)(i) benzoic acid [1] 1 7(c)(ii) COOH directs 3 position [1] 1 7(c)(iii) electrophilic substitution [1] 1 7(c)(iv) M1 curly arrow from within hexagon towards CH C+=O [1] 3 3 M2 correct intermediate [1] M3 curly arrow from C–H bond into hexagon and correct product Q [1] 7(c)(v) MnO – / KMnO / manganateVII / permanganate aq / H+ / acidified / OH– then acid / alkaline then 1 4 4 acid heat / boil / reflux / T>50o OR alkaline iodine followed by acidification [1] Question Answer Marks

8(a) 120° AND sp2 1 8(b)(i) C H Cl + AlCl → CH CH + + AlCl – 1 2 5 3 3 2 4 © UCLES 2022 Page 14 of 16 8(b)(ii) 3 curly arrow 1 AND curly arrow 2 [1] correct intermediate structure [1] C H C H AND H+ [1] 6 5 2 5 8(c)(i) (aqueous / alkaline) AgNO / silver nitrate 1 3 8(c)(ii) C H Cl + H O → C H OH + HCl 1 2 5 2 2 5 / C H Cl + NaOH → C H OH + NaCl 2 5 2 5 AND Ag+ + Cl – → AgCl AND NO equation shown for C H Cl 6 5 8(c)(iii) lone pair / p-orbital from Cl overlaps with benzene ring 1 AND stronger / partial double C-Cl bond OR difficult to break C-Cl bond Question Answer Marks

8(a) 120° AND sp2 1 8(b)(i) C H Cl + AlCl → CH CH + + AlCl – 1 2 5 3 3 2 4 © UCLES 2022 Page 14 of 16 8(b)(ii) 3 curly arrow 1 AND curly arrow 2 [1] correct intermediate structure [1] C H C H AND H+ [1] 6 5 2 5 8(c)(i) (aqueous / alkaline) AgNO / silver nitrate 1 3 8(c)(ii) C H Cl + H O → C H OH + HCl 1 2 5 2 2 5 / C H Cl + NaOH → C H OH + NaCl 2 5 2 5 AND Ag+ + Cl – → AgCl AND NO equation shown for C H Cl 6 5 8(c)(iii) lone pair / p-orbital from Cl overlaps with benzene ring 1 AND stronger / partial double C-Cl bond OR difficult to break C-Cl bond Question Answer Marks

5(a) any three points from: 3 • bond angle = 120° AND shape is hexagonal ring planar / trigonal planar • (carbons are) sp2 hybridised • contains delocalised electrons in the  bonds / system • (sp2 orbitals) overlap end-on-end/ head-on to form  bonds • a p orbital (from each carbon atom) overlaps sideways (with each other above and below the ring) forming  bonds 5(b)(i) Cl + AlCl → Cl+ + AlCl – 1 2 3 4 © UCLES 2023 Page 12 of 17 5(b)(ii) 3 + H+ M1 curly arrow from inside hexagon of aromatic ring to Cl + CON going to a lone pair on Cl M2 intermediate M3 curly arrow from C—H bond to inside the ring AND H+ 5(c)(i) electrophilic substitution 1 © UCLES 2023 Page 13 of 17 5(c)(ii) 1 OR 4-substituted acyl / alkyl derivative ALLOW 3-substituted acyl / alkyl derivative © UCLES 2023 Page 14 of 17 5(c)(iii) (most) acyl chloride > alkyl chloride > aryl chloride (least) 1 any two from: 2 • acyl chlorides: carbon (in C—Cl) is more electron deficient AND it is also attached to an oxygen atom / two electronegative atoms OR C—Cl bond is weakest / weakened in acyl chlorides AND 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 on Cl delocalises with  ring so C—Cl bond is stronger • alkyl chlorides carbon atom has a smaller + AND due to the carbon being only attached to one electronegative atom OR C—Cl bond strengthened AND by electron donating effect / positive inductive effect of alkyl / R group 5(d) (CH ) CNH (in ethanol) [substitution] } in either order 1 3 3 2 LiAlH OR NaBH [reduction ] } in either order 1 4 4 1 [substitution first] OR [reduction first] 5(e)(i) rotate the plane of polarised light in the opposite direction 1 OR stereoisomers / molecules that are non-superimposable mirror images 5(e)(ii) need to separate the optical isomers to form the pure active isomer 1 OR reduced / different biological activity of ‘other’ enantiomer OR lower yield of biologically active molecule / desired molecule 5(e)(iii) chiral catalyst OR use of an enzyme 1 © UCLES 2023 Page 15 of 17 5(f)(i) ten / 10 1 5(f)(ii) ( = 0.9–1.7) 3 • 9H • singlet • –CH / alkane 3 ( = 3.2–4.0) / ( = 2.3–3.0) • 1H • triplet • –CHO / alkyl next to electronegative atom OR Ar-CH / alkyl next to aromatic ring ( = 6.0–9.0) • 4H • multiplet • H–Ar / attached to aromatic ring any three [1] any six [2] all nine [3] Question Answer Marks

5(a)(i) 3 M1 M2 M3 BOTH 5(a)(ii) M1 reaction 1: hydrogenation / reduction 2 M2 mechanism 2: (free) radical substitution 5(b) the substitution product is stabilised by delocalization of -electrons / by -electrons in the ring 1 OR the addition product is not stabilised by delocalisation (of -)electrons ALLOW addition product will remove -electron delocalised system © UCLES 2023 Page 12 of 19 5(c)(i) 3 M1 curly arrow from inside the hexagon to S atom M2 structure of the intermediate M3 curly arrow from C-H bond into the ring AND formation/loss of H+ 5(c)(ii) 1 5(d)(i) CH COOH + SOBr  CH COBr + HBr + SO 1 3 2 3 2 © UCLES 2023 Page 13 of 19 5(d)(ii) M1 acyl bromides > acyl chlorides > alkyl chlorides 3 easiest hardest M2 M3 Any two from: Acyl bromides easiest  in acyl bromides C–Br is much weaker ORA AND due to less orbital overlap / Br having a larger atomic radii Acyl halides easier than alkyl chlorides  carbon in C–Cl / C–Br / C–X bond is more +/electron deficient OR C–Cl / C–Br bond is weaker (than C-Cl in alkyl chlorides) AND attached to an oxygen atom / two electronegative atoms / electron withdrawing C=O group ORA alkyl chlorides hardest  in alkyl chlorides C–Cl bond strengthened AND by positive inductive effect / electron donating effect of alkyl / R group Question Answer Marks

7(a) CH Cl + AlCl [1] 2 3 3 hot alkaline) MnO – [1] 4 © UCLES 2023 Page 9 of 14 7(b) 4, 110-160, 2 1, 25-50 either order [1] 4, 110-160, 1, 160-185 either order [1] 7(c)(i) Mark J and K together. 4 either or J or K [1] J or K [1] for the ring substituted product – AlCl [1] 3 for the side-chain substituted product – uv [1] © UCLES 2023 Page 10 of 14 7(c)(ii) 3 L [1] M [1] PCl + heat OR SOCl OR PCl [1] 3 2 5

6(a)(i) ratio of the concentrations of solute in two solvents 1 6(a)(ii) M1 10.5 = (y ÷ 25) ÷ ((0.74–y) ÷ 40) 2 M2 y = 0.642 g 6(b) 2 sp sp2 sp3 Kekulé benzene 0 6 0 Dewar benzene 0 4 2 Ladenburg benzene 0 0 6 M1 row 1 and 2 correct M2 row 3 correct 6(c) M1 120° AND hexagonal/trigonal planar 2 M2 C-C has -bonds and -bonds AND C-H have -bonds only 6(d) bond strain OR ring strain 1 6(e) 1 peaks Dewar benzene 2 Ladenburg benzene 1 delocalised benzene 1 6(f)(i) BrCH CH CH CH Br + FeBr → BrCH CH CH CH + + FeBr – 1 2 2 2 2 3 2 2 2 2 4 © Cambridge University Press & Assessment 2024 Page 10 of 18 6(f)(ii) 3 M1 curly arrow from inside the hexagon towards C+ M2 structure of the intermediate M3 curly arrow from C–H bond into the ring AND H+ © Cambridge University Press & Assessment 2024 Page 11 of 18 6(f)(iii) M1 Y 2 M2 Z O OR Question Answer Marks

6(a)(i) ratio of the concentrations of solute in two solvents 1 6(a)(ii) M1 10.5 = (y ÷ 25) ÷ ((0.74–y) ÷ 40) 2 M2 y = 0.642 g 6(b) 2 sp sp2 sp3 Kekulé benzene 0 6 0 Dewar benzene 0 4 2 Ladenburg benzene 0 0 6 M1 row 1 and 2 correct M2 row 3 correct 6(c) M1 120° AND hexagonal/trigonal planar 2 M2 C-C has -bonds and -bonds AND C-H have -bonds only 6(d) bond strain OR ring strain 1 6(e) 1 peaks Dewar benzene 2 Ladenburg benzene 1 delocalised benzene 1 6(f)(i) BrCH CH CH CH Br + FeBr → BrCH CH CH CH + + FeBr – 1 2 2 2 2 3 2 2 2 2 4 © Cambridge University Press & Assessment 2024 Page 10 of 18 6(f)(ii) 3 M1 curly arrow from inside the hexagon towards C+ M2 structure of the intermediate M3 curly arrow from C–H bond into the ring AND H+ © Cambridge University Press & Assessment 2024 Page 11 of 18 6(f)(iii) M1 Y 2 M2 Z O OR Question Answer Marks

7(a) aluminium chloride OR AlCl [1] 1 3 7(b)(i) delocalised system / delocalised ring / pi system / pi ring [1] 2 C–Cl bond [1] 7(b)(ii) C–H bond [1] 2 delocalised system / delocalised ring / pi system / pi ring [1] 7(c) 0, 5, 1 [1] 1 7(d) C H + Cl → C H Cl + HCl [1] 1 6 6 2 6 5 7(e) Cl + 1 hydrogen / H chlorine / Cl [1] 7(f)(i) nucleophilic substitution AND ethanol [1] 1 7(f)(ii) delocalisation of LP of Cl with  system [1] 2 C–Cl bond is stronger in chlorobenzene / partly double [1] © Cambridge University Press & Assessment 2024 Page 10 of 12

8(a)(i) Br + AlBr → Br+ + AlBr – 1 2 3 4 8(a)(ii) 2 • reference to methyl group having an effect • methyl group is 2,4,6 directing Correct structure and one correct point [1] correct structure and two correct points [2] 8(a)(iii) 3 → → M1: first curly arrow from inside hexagon towards Br+ M2: correct intermediate M3: second curly arrow from bond into hexagon AND organic product, H+ 8(b)(i) chlorobutane AND white precipitate 1 8(b)(ii) M1: C 4 H 9 Cl + H 2 O → C 4 H 9 OH + H+ + Cl – 2 M2: Cl – + Ag+ → AgCl [1] © Cambridge University Press & Assessment 2025 Page 14 of 16 8(b)(iii) M1: delocalisation of lone pair of Cl into benzene ring /  system 2 M2: strengthens C–Cl bond / causes C–Cl bond to have partial double bond nature

8(a)(i) Br + AlBr → Br+ + AlBr – 1 2 3 4 8(a)(ii) 2 • reference to methyl group having an effect • methyl group is 2,4,6 directing Correct structure and one correct point [1] correct structure and two correct points [2] 8(a)(iii) 3 → → M1: first curly arrow from inside hexagon towards Br+ M2: correct intermediate M3: second curly arrow from bond into hexagon AND organic product, H+ 8(b)(i) chlorobutane AND white precipitate 1 8(b)(ii) M1: C 4 H 9 Cl + H 2 O → C 4 H 9 OH + H+ + Cl – 2 M2: Cl – + Ag+ → AgCl [1] © Cambridge University Press & Assessment 2025 Page 14 of 16 8(b)(iii) M1: delocalisation of lone pair of Cl into benzene ring /  system 2 M2: strengthens C–Cl bond / causes C–Cl bond to have partial double bond nature

5(a) M1 and M2: any two [1], all three [2] 4 • (hexagonal ring) planar / (trigonal) planar • 120o • sp2 hybridised M3: p orbitals overlap sideways / laterally (with each other above and below the ring) forming  bonds M4:  bonds form when sp2 / hybridised orbitals overlap end-on-end / head on 5(b)(i) M1: (reaction 5) Pt / Ni + H (+ heat) 2 2 M2: (reaction 6) (CH 3 ) 2 CHCOCl + AlCl3 (+ heat) 5(b)(ii) reduction / hydrogenation 1 5(c)(i) (CH CH group) directs to 2-, 4- (and 6-) positions AND due to being an electron donating group 1 2 3 5(c)(ii) CH CH Br + FeBr → CH CH + + FeBr – 1 3 2 3 3 2 4 5(c)(iii) 3 organic intermediate M1: curly arrow from inside / touching the hexagon to (CH ) group / C+ charge 2 M2: structure of the intermediate M3: curly arrow from C-H bond into / onto the ring AND formation / loss of H+ 5(c)(iv) H+ + FeBr – → HBr + FeBr 1 4 3 © Cambridge University Press & Assessment 2025 Page 12 of 16