A-Level Chemistry: Organic Analysis and Synthesis

The analysis topic is where A-level organic chemistry becomes detective work: given spectra and test results, identify the molecule. This quiz assembles the full evidence toolkit the way structure-determination questions deploy it.

The wet-chemistry questions cover the bench tests: propanal identified by Tollens' silver mirror and Fehling's brick-red precipitate, and the synthesis-planning question that oxidises propan-1-ol to propanoic acid under reflux.

The spectroscopy questions carry the analytical weight. Mass spectrometry is tested through fragment arithmetic — the loss of 15 from m/z 74 to 59 pointing to a methyl group. Infrared appears as the two-peak logic puzzle: broad O-H plus sharp C=O reading as carboxylic acid. Proton NMR gets the full apparatus: the n+1 splitting rule (a quartet meaning three neighbours), TMS as reference with its twelve equivalent upfield protons, and deuterated chloroform's silence in the proton region. Carbon-13 NMR is covered through environment counting, and the capstone question combines IR and ¹³C evidence to identify butanone among its C₄H₈O isomers — the genuinely synoptic move.

Chromatography completes the set with the Rf definition.

Each explanation walks the deductive chain from data to structure, which is exactly the skill the structure-determination question rewards. This quiz is the natural final step after Organic I and II in this collection: first learn the reactions, then identify their products.

  • Select and interpret bench tests for functional groups
  • Read mass spectra through molecular ion and fragment losses
  • Interpret IR absorptions and combine them into functional-group conclusions
  • Apply proton NMR splitting, integration and reference conventions
  • Combine spectra to distinguish isomers and plan synthesis routes

Aligned to the organic analysis content of the DfE A level science subject content: qualitative tests, mass spectrometry, infrared spectroscopy, proton and carbon-13 NMR, chromatography and synthesis planning.

Sample question

An unknown organic compound X produces a molecular ion peak at m/z 74 in mass spectrometry. A peak at m/z 59 is also observed. Which fragment loss corresponds to the difference between these two peaks?

See the answer

Loss of a methyl group

The difference between 74 and 59 is 15. A mass of 15 corresponds to a methyl group (CH3).

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