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Logic Puzzle #7: Almost Missed It … Solution

September 20, 2010
by Arvin Moser, Team Manager, Application Scientists, ACD/Labs

‘How many signals are present?’ is such a simple question, and yet, it is a fundamental question to an elucidator. Mistaken a signal or overlook one and the elucidator can run the risk of wasting time and effort.

 

The 13C [1H] NMR spectrum below shows 3 discernible signals that are attributed to the solvent CDCl3. In addition, one can begin to speculate on weaker signals; there might a fourth signal at ~77.2 ppm (most likely due to residual CHCl3), possibly a fifth at ~77.5 ppm, perhaps a sixth one at ~77.3 ppm and maybe more.

 

Logic#7PeakOverlapCDCl3_13Cc_Sept212010

The next step is to examine additional data and verify whether the ‘weak’ signals are real or not. This can include:

1. comparing the weak signals to other structural signals,

2. applying deconvolution/peak fitting to this region,

3. checking 2D NMR data,

4. acquiring data in a different solvent,

5. modifying the acquisition parameters to exclude the solvent or increase S/N, etc.


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One Reply to “Logic Puzzle #7: Almost Missed It … Solution”

  1. Hi,
    I might be wrong, but I believe that the peak at 77.2ppm is due to residual CHCl3.
    By the way, congratulation on your blog.
    Cheers
    Manuel

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