Example 13C NMR Spectra
Here are a couple of examples for judging 13C chemical shifts:
Remember that 13C shifts generally follow the pattern of 1H shifts, but are much larger.
Thus, in (a)
- The peak at lowest field is the caarbon with the OH attached
- The peak at highest field is the CH3 farthest from the OH
- Generally in both 13C and 1H spectra, CH2 groups fall to lower field than CH3, which assigns the remaining peaks.
- The peak at lowest field is the C=O carbon, shifted by electronegativity and "diamagnetic anisotropy"
- Assignment of the other two peaks follows from the CH2 lower than CH3 rule.
Now try predicting the splitting pattern to be found if the decoupler is turned off.
This page last modified 12:46 PM on Monday November 5th, 2012.
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