Nuclear Magnetic Resonance Spectroscopy Spectroscopy ¢â‚¬¢ Nuclear Magnetic Resonance ¢â‚¬â€œ Absorption and

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  • Nuclear Magnetic Resonance Spectroscopy

    Presented by: Reitumetse Nkhahle

  • Nuclear Magnetic Resonance (NMR) Spectroscopy

    • Nuclear Magnetic Resonance – Absorption and re-emission of electromagnetic

    radiation.

    • Spectroscopy – Technique used to measure light scattered,

    absorbed or emitted by matter.

  • Principles of NMR • Subatomic particles have a spin. • Nuclei with a ½ spin behave like a magnet: Figure 1: Nuclei interaction with external magnetic field.

    • Examples of elements with nuclei that have a spin of ½:

    – 13C – 1H – 15N

    Image sourced from: http://www.chem.ucla.edu/~harding/notes/notes_14C_nmr02.pdf

    http://www.chem.ucla.edu/%7Eharding/notes/notes_14C_nmr02.pdf

  • The NMR Spectrometer

    • Continuous wave spectrometer – Outdated – Solid-state NMR applications

    • Fourier transform spectrometer – Signal is measured in time (s) – Fourier transform converts signal measured in

    time-domain to a frequency vs intensity plot.

  • The Fourier Transform Spectrometer

    Figure 2: Illustration of an FT-NMR spectrometer.

    Image sourced from: http://chem4823.usask.ca/nmr/magnet.html.

    http://chem4823.usask.ca/nmr/magnet.html

  • Experimental factors

    • Tuning • Shimming • Locking • Temperature • Sample preparation

  • Detection of the NMR signal

    Figure 3: Image illustrating the production of NMR spectra.

    Images sourced from: http://image.slidesharecdn.com/bt63116nmr1-140325231614-phpapp02/95/bt63116nmr1- 16-638.jpg?cb=1395789681 and http://slideplayer.hu/slide/2028189/.

    http://slideplayer.hu/slide/2028189/ http://slideplayer.hu/slide/2028189/ http://slideplayer.hu/slide/2028189/ http://slideplayer.hu/slide/2028189/ http://slideplayer.hu/slide/2028189/ http://slideplayer.hu/slide/2028189/ http://slideplayer.hu/slide/2028189/ http://slideplayer.hu/slide/2028189/ http://slideplayer.hu/slide/2028189/ http://slideplayer.hu/slide/2028189/ http://slideplayer.hu/slide/2028189/

  • Types of NMR spectra 1H NMR 13C NMR

    Figure 4: 1-dimensional NMR spectra of carbon-13 and hydrogen.

    Images sourced from: http://www.odinity.com/wp-content/uploads/2014/01/NMR_benzene.png and http://www.chemguide.co.uk/analysis/nmr/c13acrylate.gif.

    http://www.odinity.com/wp-content/uploads/2014/01/NMR_benzene.png http://www.chemguide.co.uk/analysis/nmr/c13acrylate.gif

  • Types of NMR spectra Homonuclear correlation spectroscopy (COSY)

    Heteronuclear multiple-bond correlation spectroscopy (HMBC)

    Figure 5: Examples of 2-dimensional NMR spectra. Images sourced from: http://img.dxycdn.com/upload/2005/09/29/24419253.gif and http://131.104.156.23/Lectures/CHEM_207/CHM_207_Pictures_NMR/NMR_2D_COSY_color.gif.

    http://img.dxycdn.com/upload/2005/09/29/24419253.gif http://131.104.156.23/Lectures/CHEM_207/CHM_207_Pictures_NMR/NMR_2D_COSY_color.gif

  • Interpreting NMR spectra – chemical shifts

    Figure 6: Chemical shifts for proton and carbon-13 NMR.

    Image source from: http://image.slidesharecdn.com/nmr-140924032539-phpapp02/95/nmr-spectroscopy-47- 638.jpg?cb=1411529227.

    http://image.slidesharecdn.com/nmr-140924032539-phpapp02/95/nmr-spectroscopy-47-638.jpg?cb=1411529227 http://image.slidesharecdn.com/nmr-140924032539-phpapp02/95/nmr-spectroscopy-47-638.jpg?cb=1411529227

  • Advantages

    • Provides both qualitative and quantitative information.

    • Samples can be recovered. • A small quantity of material is required for

    analysis. • Preparation of sample is easy.

  • Disadvantages

    • Poor sensitivity. • Requires special infrastructure and training. • Spectra takes a long time to interpret. • Potential fire hazard. • Very expensive.

  • Applications

    • Compound identification and confirmation. • Chemical composition determination. • Molecular conformation determination.

    • Raw materials fingerprinting.

    • Quality assurance and control.

  • Thank you.

    Nuclear Magnetic Resonance Spectroscopy Nuclear Magnetic Resonance (NMR) Spectroscopy Principles of NMR The NMR Spectrometer The Fourier Transform Spectrometer Experimental factors Detection of the NMR signal Types of NMR spectra Types of NMR spectra Interpreting NMR spectra – chemical shifts Advantages Disadvantages Applications Thank you.

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