NMR After Assignment: Relaxation, Distance and Exchange · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

What NMR says after assignment

Science · Chemistry · ages 22-23
Name ______________________   Date ____________

  1. What does a through-space enhancement measure?

    • Bond strength between atoms
    • Separation in space between nearby nuclei
    • The sample temperature

  2. What does a short longitudinal relaxation time report?

    • The nucleus is perfectly isolated
    • The nucleus sheds energy fast to its surroundings
    • The magnet has failed

  3. A signal that broadens and then splits on cooling shows an exchanging process.

    Circle one:   True   False

  4. A nucleus near a paramagnetic centre relaxes very fast. Why?

    • The magnet is too strong
    • The sample tube is dirty
    • The neighbour offers a rapid energy pathway

  5. Two assignments fit the shifts. Irradiating proton A enhances proton B. What follows?

    • The assignment putting A far from B
    • Neither assignment, the data is useless
    • The assignment putting A close to B

  6. Two peaks overlap hopelessly at your field. What is worth trying?

    • The same experiment at another field strength
    • Shaking the sample tube
    • Deleting one of the peaks

  7. No enhancement appears between two protons that shifts suggest are close. What should you suspect?

    • The distance is larger than assumed, or motion averages it away
    • The assignment is settled anyway
    • Enhancements always appear regardless

  8. A spectrum broadens on warming and sharpens on cooling without splitting. What is the best reading?

    • A process moving toward the measurement timescale from the slow side
    • Proof of an impurity
    • Proof the magnet drifted
LightMySky · lightmysky.comW1-mt_dCV2EbNlF2-s1

Answer key

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

What NMR says after assignment W1-mt_dCV2EbNlF2-s1

  1. Separation in space between nearby nuclei · Cross-relaxation only reaches nuclei that sit close.
  2. The nucleus sheds energy fast to its surroundings · Fast energy loss means an efficient nearby pathway.
  3. True · Cooling slows the exchange until both partners resolve.
  4. The neighbour offers a rapid energy pathway · Short T1 reports an efficient surrounding, such as a paramagnetic neighbour.
  5. The assignment putting A close to B · Enhancement proves closeness, which only one candidate allows.
  6. The same experiment at another field strength · Separation scales with field, so a new field can resolve them.
  7. The distance is larger than assumed, or motion averages it away · Missing cross-relaxation challenges the closeness claim.
  8. A process moving toward the measurement timescale from the slow side · Temperature-dependent width tracks exchange near the measurement timescale.
Worksheet · LightMySky