Unstable, uncharged intermediates: every question, 2016 to 2025

Notes: Molecular rearrangements (full notes) · short notes

Notes: Reactive intermediates: carbocations, carbanions, radicals, carbenes, nitrenes, benzyne (full notes) · short notes

2025

• Q6(a) Singlet and triplet carbenes; fluorenylidene with cis-but-2-ene4 marks Answered
• Q7(a)(i) p-Cresol: Reimer–Tiemann reaction, then a cyanohydrin5 marks Answered
• Q7(a)(ii) 2-Naphthoic acid to a urethane: Curtius rearrangement5 marks Answered

2024

• Q6(a) Curtius rearrangement; the isocyanate closes to a cyclic urea4 marks Answered
• Q10(a)(i) Anisole with dibromocarbene: ring expansion to a tropone5 marks Question only

2023

• Q6(a) Chlorocarbene from CH₂Cl₂; ring expansion of 3-methylindole4 marks Answered
• Q7(a) Hofmann rearrangement; proof that it is intramolecular10 marks Answered

2022

• Q6(j) 4-Bromobenzoyl chloride to 4-bromoaniline: Lossen rearrangement4 marks Answered

2021

• Q10(c) Urea, amine and carbamate from benzoic acid (Curtius route)10 marks Answered

2020

• Q6(a) Dichlorocarbene ring expansion4 marks Answered
• Q7(a) Ketone with excess HN₃ in H₂SO₄10 marks Question only
• Q7(c) Identify A and B in an acyl azide sequence5 marks Question only

2019

• Q6(h) Schmidt reaction of cinnamic acid4 marks Answered

2018

• Q9(a) Chlorotriphenylmethane with silver: the trityl radical5 marks Question only

2016

• Q7(b) Dichlorocarbene addition4 marks Answered
• Q7(h) Hofmann rearrangement and oxidation4 marks Answered
• Q9(c) Stereochemistry of Hofmann rearrangement5 marks Answered
• Q10(b) Aromatic ammonium ylide5 marks Answered
• Q10(c) Benzyne generation and trapping5 marks Answered