Spin-spin
coupling: In NMR
spectroscopy, the effect of one nucleus's magnetic field
on other nuclei within the molecule,
causing splitting
of the NMR
signals.
Spin-spin
coupling occurs only when the nuclei in question have I ≠ 0.
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| Ha does not
couple with any other protons. The 1H-NMR signal for Ha is a singlet at 6.69 ppm. Click on image for larger version. |
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The Ha/Hb
spin
system has two possible energy states: spins
parallel and spins
antiparallel. The 1H-NMR signals for Ha and Hb are both doublets, 6.28 ppm and 6.00 ppm. Click on image for larger version. |