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Spectroscopy learning guide

NMR Spectroscopy Interactive Learning Guide

Explore nuclear spin, resonance frequency, chemical shift, integration, and splitting with a browser-based NMR spectroscopy model and worked spectrum.

Open the NMR spectroscopy lab →

Change field strength, sample, coupling, and noise while inspecting the spectrum.

Start with the model

Concept overview

Nuclear magnetic resonance spectroscopy uses magnetic nuclei as local probes of molecular structure. In an external magnetic field, spin states have different energies. Radiofrequency energy can drive transitions when its frequency matches the energy gap. For proton NMR, the electronic environment slightly shields each proton, producing chemical shifts that help distinguish chemically different hydrogen environments.

A spectrum combines several kinds of evidence: the number and positions of signals suggest distinct environments, integrated areas estimate relative proton counts, and spin-spin splitting reveals certain neighbouring protons. SciFunLab's visual model separates field strength, resonance, signal position, splitting, and noise so you can reason about each effect. It is an educational first-order model, not an instrument-control or clinical interpretation system.

Concept 1

Resonance

The energy separation between nuclear spin states grows with magnetic field. Resonance occurs when the applied radiofrequency supplies the matching energy difference.

Concept 2

Chemical shift

Electron density changes the local field at a nucleus. Chemical shift in parts per million makes signal positions comparable across spectrometers of different field strengths.

Concept 3

Integration and splitting

Integrated signal area is proportional to the number of contributing protons under suitable conditions. Coupling to n equivalent neighbouring protons often produces n + 1 lines in simple first-order spectra.

Guided investigation

What changes when magnetic field strength increases?

  1. 1Select a proton sample and compare the zero-field view with a nonzero magnetic field.
  2. 2Record resonance frequency at two available field strengths while keeping the nucleus fixed.
  3. 3Choose a simple spectrum and identify signal count, integration, and multiplicity separately.
  4. 4Increase the noise level, then use the cryoprobe/noise control and describe which evidence becomes easier to distinguish.

Evidence to record

Record field, nucleus, resonance frequency, chemical shifts, integrals, multiplicities, and noise setting. Separate observations made directly from interpretations about structure.

Equations and variables

Delta E = h nu

Relates the spin-state energy separation to the resonance frequency.

  • • Delta E: energy difference
  • • h: Planck constant
  • • nu: resonance frequency

delta(ppm) = (nu_sample - nu_ref) / nu_spectrometer x 10^6

Defines chemical shift relative to a reference frequency.

  • • delta: chemical shift
  • • nu_sample and nu_ref: sample and reference frequency
  • • nu_spectrometer: operating frequency

Worked example

Apply the model

A simple proton environment has two equivalent neighbouring protons and integrates to three hydrogens. Predict its first-order multiplicity and relative proton count.

  1. Step 1: Apply the n + 1 rule with n = 2 equivalent neighbours, giving 3 lines.
  2. Step 2: Use the integral independently: the signal area represents three contributing protons relative to other signals.

Answer: Predict a triplet integrating to three protons. Multiplicity reports neighbouring coupling; integration reports the relative number contributing to the signal.

Misconceptions to test

Common claim

“NMR uses dangerous ionising radiation like X-rays.”

Correction: NMR spectroscopy uses radiofrequency electromagnetic energy; the cited introductory treatment describes much smaller photon energies than infrared, though strong magnets still require strict safety controls.

Common claim

“A taller peak always means more protons.”

Correction: Relative integrated area, not peak height alone, estimates proton count. Splitting, line width, overlap, and acquisition conditions all affect height.

Teacher-ready worksheet

Introductory proton NMR evidence sheet

  1. 1.Label field, energy gap, and resonance frequency on one diagram.
  2. 2.Distinguish chemical shift, integration, and splitting in your own words.
  3. 3.Predict multiplicity for n = 0, 1, 2, and 3 equivalent neighbours.
  4. 4.Interpret one simple simulated spectrum.
  5. 5.List two reasons the classroom model may differ from a measured spectrum.

Print or save this page as PDF to use the investigation and worksheet offline.

Knowledge check

Check your understanding

Answer four questions on resonance, shifts, integration, and splitting with immediate verified feedback.

Take the NMR knowledge check →

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