Unit 4 is the advanced organic chemistry modular component of the OxfordAQA International A-Level qualification. It broadens the fundamental mechanisms studied in AS Unit 2 into complex nucleophilic additions, nucleophilic addition-eliminations, electrophilic aromatic substitutions, condensation polymerisations, proteins, and NMR spectroscopy.
Like Unit 3, Unit 4 is examined in both the January series and the May/June series. Candidates benefit from sit and resit opportunities to lock in an optimal UMS score before cashing in the full A-Level.
Examiners place extraordinary weight on curly arrow precision. Arrows must originate unambiguously from a lone pair of electrons or the centre of a covalent bond, and terminate precisely on the destination atom or bond. Differentiating nucleophilic addition (carbonyls) from nucleophilic addition-elimination (acyl chlorides/anhydrides) is vital.
Full written paper (80 marks) with AI marking, plus 15 warm-up multiple-choice questions.
Select a syllabus node below to access comprehensive revision notes, illustrated mechanisms, worked synthesis routes, and exam-style practice questions:
Rate expressions (rate = k[A]^m[B]^n), reaction orders, initial rate methods, rate-determining steps in multi-step mechanisms, and Arrhenius plots of ln k against 1/T to deduce activation energy.
Open Topic Notes →Gas phase equilibrium calculations, mole fractions, partial pressures, Kp expressions and unit deductions, ICE table calculations, and the response of Kp to temperature, pressure, and catalysts.
Open Topic Notes →Chiral carbon stereocentres, non-superimposable mirror image enantiomers, polarimetry plane-polarised light rotation, and racemic mixture formation from planar carbonyl groups.
Open Topic Notes →Structure and reactivity of carbonyls, oxidation tests with Tollens and Fehling reagents, reduction using NaBH₄, and nucleophilic addition mechanisms with KCN / HCN.
Open Topic Notes →Carboxylic acids, esterification, base hydrolysis (saponification), acyl chlorides, acid anhydrides, and nucleophilic addition-elimination mechanisms.
Open Topic Notes →Kekule vs delocalised ring model, thermodynamic stability evidence from hydrogenation enthalpies, and electrophilic substitution mechanisms (nitration and Friedel-Crafts acylation).
Open Topic Notes →Classification of amines, comparative Bronsted-Lowry base strengths, nucleophilic substitution syntheses, reduction of nitriles and nitrobenzene, and quaternary ammonium salt cationic surfactants.
Open Topic Notes →Step-growth condensation polymers, Terylene (PET) polyester, Nylon 6,6 and Kevlar polyamides, repeating unit identification, hydrolysis breakdown, and comparison with addition polymers.
Open Topic Notes →Zwitterions, peptide bond formation, primary, secondary and tertiary protein structure, and how the anticancer drug cisplatin acts.
Open Topic Notes →Designing processes with no solvent, safe starting materials, fewer steps and high atom economy, a reaction map of 9620 reactions, and worked syntheses of up to four steps.
Open Topic Notes →Carbon-13 (¹³C) and proton (¹H) NMR: solvents and the TMS standard, chemical shifts, integration and (n+1) splitting patterns.
Open Topic Notes →Thin-layer, column and gas chromatography, Rf values and retention times, GC-MS, and identifying amino acids by TLC.
Open Topic Notes →