Advanced Organic Synthesis & Purification Labs for H2 Chemistry Paper 4
Download printable cheat-sheet (CC-BY 4.0)17 Nov 2025, 00:00 Z
Join our Telegram study groupQ: What does Advanced Organic Synthesis & Purification cover?
A: Step-by-step Paper 4 workflows for reflux, distillation, liquid–liquid extraction, recrystallisation, chromatography, and yield tracking-plus ACE commentary frameworks grounded in MOE’s 2025 syllabus.
TL;DR
Organic tasks combine synthetic precision with safety discipline.
Control heating, phase separations, drying, and purity calculations so you can justify every observation and improvement during Paper 4.
1 | Organic investigations in the 2025 syllabus
- The MOE H2 Chemistry practical guidance highlights organic synthesis and purification as recurring contexts, building on Qualitative Analysis Annex tests. Candidates must demonstrate safe manipulation, accurate observation, and evaluative commentary.
- Examiner reports often flag incomplete purification, poor yield documentation, and missing safety controls (e.g., reflux set-ups lacking clamps or open joints).
- The 9476 Paper 4 specimen for 2026 backs this up-Question 2 walks through an organic preparation, TLC confirmation, and yield discussion, echoing the reflux, extraction, and purification checkpoints summarised here.
- Common Paper 4 scenarios: esterification under reflux, nitration, oxidation/reduction, separation of product from by-products, determination of purity via melting point or TLC.
2 | Reflux & distillation mastery
- Apparatus: round-bottom flask, anti-bumping granules, Liebig or Allihn condenser (water in at bottom/out at top), heating mantle/hot plate, drying tube (when excluding moisture).
- Reflux steps: charge reagents, add anti-bumping granules, clamp securely, start coolant before heating, maintain gentle boil (liquid should return without climbing condenser).
- Distillation: switch to a still head with thermometer adapter and receiving adapter; monitor temperature plateau to identify fraction.
- Troubleshooting:
- Bumping: add more anti-bumping granules or reduce heat.
- Loss of volatile reagent: ensure condenser cold water flow is sufficient.
- Fraction contamination: insulate still head, collect fractions within narrow temperature windows.
Safety reminder: Keep flammable solvents away from naked flames; use mantles or water baths. Note any vapour releasing (e.g., HCl) and operate in a fume hood.
