Reading a Proton NMR Spectrum: Shift, Integration and Multiplicity · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Reading a proton spectrum in three clues

Science · Chemistry · ages 20-21
Name ______________________   Date ____________

  1. A proton spectrum shows three signals with relative areas 1:2:3. The molecule holds 12 protons in total. How many protons sit behind the largest signal?

    Answer: ______________

  2. Protons sit next to an oxygen atom. Where does their signal slide?

    • Upfield with the plain alkyl protons
    • Downfield, since oxygen pulls density away
    • Off the spectrum entirely in every case

  3. A proton set has two equivalent protons on the neighbouring carbon. What pattern appears?

    • A triplet, by the n plus one rule
    • A singlet, since neighbours never matter
    • A quartet, since every set gives four peaks

  4. Three signals show relative areas 1 to 2 to 3, and the molecule holds 12 protons. How many sit behind the largest signal?

    Answer: ______________

  5. A signal vanishes after the sample is shaken with deuterium oxide, which proves it came from an OH or NH proton.

    Circle one:   True   False

  6. A spectrum shows three signals with relative areas 1:1:2, and the formula holds 8 protons. How many protons give the largest signal?

    • 4
    • 2
    • 1
    • 8

  7. A signal appears as a quartet. How many equivalent neighbours sit next door?

    • Four equivalent neighbours
    • Three equivalent neighbours
    • No neighbours at all

  8. Ethanol and dimethyl ether share a formula of six protons, yet one shows three signals and the other one. Why?

    • The spectrometer counts atoms differently for each compound
    • Same atoms in different neighbourhoods split into different proton sets
    • One of the spectra was recorded incorrectly

  9. A proposed structure matches the shifts but its integrals sum to 10 against a formula holding 12 protons. What is the verdict?

    • Accept it, since shift alone decides every structure
    • Adjust the spectrometer until the numbers fit
    • Reject it, since integrals must sum to the formula total alongside shift and splitting

  10. Three signals show relative areas 2 to 3 to 5, and the formula holds 20 protons. How many sit behind the largest signal?

    Answer: ______________

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Answer key

For grown-ups. Fold this page away before handing over the rest.

Reading a proton spectrum in three clues W1-mt_WgxqHHf-YL-s1

  1. 6 · The parts total 6 and the largest signal owns 3 of them, so it holds half of the 12 protons, which is 6.
  2. Downfield, since oxygen pulls density away · Withdrawing neighbours deshield the protons and push the signal downfield.
  3. A triplet, by the n plus one rule · Two neighbours plus one gives three peaks.
  4. 6 · The parts total 6 and the largest owns 3 of them, which is half of 12.
  5. True · Only labile protons swap with deuterium, and deuterium stays invisible in the proton spectrum.
  6. 4 · The parts total 4 and the largest owns 2 of them, so it holds half of the 8 protons, which is 4.
  7. Three equivalent neighbours · Reading the rule backwards, four peaks mean three neighbours.
  8. Same atoms in different neighbourhoods split into different proton sets · Equivalent protons share a signal, so symmetry and neighbourhoods set the signal count.
  9. Reject it, since integrals must sum to the formula total alongside shift and splitting · The sketch surviving all three tests together is the only acceptable structure.
  10. 10 · The parts total 10 and the largest owns 5 of them, which is half of 20.
Worksheet · LightMySky