NMR Integration: Match the Spectrum
Integration tells you how a molecule's hydrogens partition into equivalent sets, but different molecules can share the same partition. Here the three candidates all match the integration shown, on purpose: the ratio alone cannot decide. Read the spectrum itself — where the signals sit and how they split — and click the structure that fits all of the evidence. This is how real structure determination works: integration narrows the field, and the chemical shifts and coupling finish the job.
¹H Spectrum Reconstructed from Experimental Data
Expansion
Common Questions
How do I choose when all three structures fit the integration?
Work signal by signal. Take the clearest signal first: its chemical shift places it in an environment (near oxygen, next to a carbonyl, aromatic), and its splitting counts its neighbors. Then check each candidate: which structure actually has that group in that environment with those neighbors? One mismatch is enough to eliminate a candidate.
Why do the candidates all share the same integration ratio?
Because that makes the problem honest. In these problems integration is the given, not the answer: molecules with the same proton partition are indistinguishable by integration alone, so the deciding evidence has to come from the chemical shifts and the splitting patterns. The easier version of this game, where the ratio does decide, has its own page: Match the Molecule to the Integration.
What do the numbers on the spectrum mean?
They are the relative integrals: the area of each signal in smallest whole numbers. On a real printout the same information appears as step heights on an integral trace or as printed numbers under the peaks; we print the numbers.
Reconstructed from published data: assigned shifts from nmrshiftdb2 (CC BY-SA 4.0) · first-order rendering with typical J values.