‹ Chemistry simulationsChemistry · AS Level 9701 · 18 Carboxylic acids and derivativesFive simulations covering Topic 18: the carboxyl group and the delocalised anion that makes it acidic, how the strength changes with electron-releasing and electron-withdrawing groups, making an ester and tracing which oxygen ends up in the link, acid and alkaline hydrolysis compared, and fats, oils and soap.
A carboxylic acid is a carbonyl and a hydroxyl group on the same carbon, and that combination behaves quite unlike either of them alone. Take the hydrogen off and the charge is shared equally over both oxygens, which is exactly why the hydrogen comes off in the first place. Switch between the acid and its anion.
Carboxylic acids are weak: in a tenth-molar solution only about one molecule in a hundred has given up its proton. Put electron-withdrawing atoms near the carboxyl group, though, and the anion is stabilised further and the acid gets stronger. Compare them, then take one to the bench.
Warm a carboxylic acid with an alcohol and a little concentrated sulfuric acid and the two join, losing a molecule of water. The oxygen that ends up in the ester link comes from the alcohol. Choose the two halves and watch the ester assemble.
Esterification is reversible, so an ester can be split back into the acid and the alcohol by refluxing with dilute acid. Reflux it with alkali instead and it goes the whole way, because the carboxylate ion that forms cannot react back. Compare the two routes.
A fat is a triester of glycerol with three long-chain carboxylic acids. Boil it with sodium hydroxide and it hydrolyses into glycerol and three soap molecules, each with a charged head and a long greasy tail. Whether it is a solid fat or a liquid oil comes down to the kinks in those tails.
The carboxyl group in 3D next to its delocalised anion, with the equal carbon-oxygen bond lengths that are the evidence for the delocalisation, a pKa comparison running from methanoic acid to trichloroethanoic acid with the pH and fraction dissociated worked out for a tenth-molar solution, esterification with the oxygen from the alcohol traced into the ester link, acid hydrolysis set against alkaline hydrolysis, and triglycerides with saturated or kinked unsaturated chains boiled down into soap and glycerol.
Five simulations covering Topic 18: the carboxyl group and the delocalised anion that makes it acidic, how the strength changes with electron-releasing and electron-withdrawing groups, making an ester and tracing which oxygen ends up in the link, acid and alkaline hydrolysis compared, and fats, oils and soap.
Carboxylic acids and derivatives is a free, browser-based simulation for Cambridge International AS & A Level Chemistry 9701 (topic 18 Carboxylic acids and derivatives). The same ideas are examined in Cambridge IGCSE Chemistry 0620 (topic 11 Organic chemistry). The course is assessed in Paper 1 (Multiple Choice (AS)), Paper 2 (AS Structured), Paper 3 (Advanced Practical), Paper 4 (A Level Structured), Paper 5 (Planning, Analysis, Evaluation). Syllabus for examination in 2025-2027. There are 5 tabs, each a self-contained experiment with its own controls and live readings, and nothing to install: it runs on a laptop, tablet or classroom projector.
Full syllabus map: AS Level Chemistry 9701 topic 18.
All simulation labs · AS Level Chemistry 9701 · TheLucidSTEM home