SS asked in 科學化學 · 1 decade ago

計算化學位移(chemical shift)


能不能告訴我該怎麼去算呢? 算了好久,感覺都不太對







1 Answer

  • Anonymous
    1 decade ago
    Favorite Answer

    Chemical shift(δ)=(difference in precession frequency between two nuclei)/(operating frequency of the magnet)

    我記得chemical shift都會給兩個值,求第三個數據

    --------------------以下chemical shift的定義--------------------

    In nuclear magnetic resonance (NMR), the chemical shift describes the dependence of nuclear magnetic energy levels on the electronic environment in a molecule.Chemical shifts are relevant in NMR spectroscopy techniques such as proton NMR and carbon-13 NMR.

    An atomic nucleus can have a magnetic moment (nuclear spin), which gives rise to different energy levels and resonance frequencies in a magnetic field. The total magnetic field experienced by a nucleus includes local magnetic fields induced by currents of electrons in the molecular orbitals (note that electrons have a magnetic moment themselves). The electron distribution of the same type of nucleus (e.g. 1H, 13C, 15N) usually varies according to the local geometry (binding partners, bond lengths, angles between bonds, ...), and with it the local magnetic field at each nucleus. This is reflected in the spin energy levels (and resonance frequencies). The variations of nuclear magnetic resonance frequencies of the same kind of nucleus, due to variations in the electron distribution, is called the chemical shift. The size of the chemical shift is given with respect to a reference frequency or reference sample (see also chemical shift referencing), usually a molecule with a barely distorted electron distribution.

    The chemical shift is of great importance for NMR spectroscopy, a technique to explore molecular properties by looking at nuclear magnetic resonance phenomena.

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