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Organic Synthesis, NMR and Chromatography

Principles of NMR and the Delta Scale

  • 3 things to know
  • Papers 2 and 3

Overview

How nuclei absorb radio frequency in a magnetic field, chemical shift, and shielding.

What you need to know

Answer each one before you reveal it.

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Key term

What does an NMR spectrum measure, and against what standard?

Key term

What physical phenomenon does NMR spectroscopy exploit to provide structural information about molecules?

Key term

What type of nuclei can be detected using NMR spectroscopy?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What physical phenomenon does NMR spectroscopy exploit to provide structural information about molecules?

    Model answer

    NMR exploits the absorption of radio frequency radiation by nuclei in a magnetic field

  2. 2

    What type of nuclei can be detected using NMR spectroscopy?

    Model answer

    Nuclei with spin; at A-level these are ¹H and ¹³C

  3. 3

    Why do different nuclei in a molecule absorb radio frequency radiation at different frequencies in NMR?

    Model answer

    Nuclei in different chemical environments experience different local magnetic fields due to surrounding electrons, causing them to absorb at different frequencies

  4. 4

    What is the reference compound used to calibrate the chemical shift scale in NMR spectroscopy?

    Model answer

    Tetramethylsilane (TMS)

  5. 5

    What is the chemical shift value assigned to the reference compound in NMR?

    Model answer

    Zero (δ = 0 ppm)

  6. 6

    What symbol is used to represent chemical shift in NMR spectroscopy?

    Model answer

    δ (delta)

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