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1H NMR Prediction yields odd results

Martin Di Grandi

I am using CD 20.1.0.112 on a 2018 MBPro running Mojave 10.14.6 but this issue has been occurring since at least CD 18 or 19 with older Mac OS.

When I draw a structure and use the Predict 1H NMR shifts, sometimes I am provided with a completely bogus structure and NMR spectrum.  Some of the more common errors are that aromatic carbons are drawn with 2 hydrogens, which have odd shifts and splitting patterns.  Sometimes O and N atoms are given signals in the proton NMR when they do not have H attached.  The only workaround I have is to quit CD and restart.  But I have to be vigilant when using this app for this purpose to make sure there aren't any issues (I use this on just about all my Org Chem exams) – sometimes the errors are very subtle.  And sometimes this happens after heavy use, sometimes it happens on my first attempt.

Below is a screenshot of what a typical error looks like – two of the aromatic carbons on the right most ring have five bonds to them.  And you will note one of the errant C-H bonds on the ring makes the adjacent CH2 group a quartet at 2.15 ppm.

Has anyone else had this problem?  And if so, is there a fix?  Thanks for your help.

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Comments

3 comments

Date Votes
  • Raja RNA

    We tried to reproduce this issue ChemDraw for Mac v18.2.0.37, v19.1.1.32, v20.0.0.38, v20.1.0.112 as well as v21.0.0.28, but we couldn't. 

    Since we are not able to reproduce in-house and so far no other user reported this issue, we believe this issue is specific to your environment/installation.  Please retest the problem after clean reinstallation.  If you have access to v21.0.0.28, please upgrade to the current version.

    If you still have any issues, please contact support for further assistance.

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  • Martin Di Grandi

    Hi Raja,

    Thanks for your help.  I was afraid this might be a local issue.  I don't think v21 is compatible with Mojave (my current OSX) so I cannot upgrade to this version and as I said, this problem has been plaguing me for several versions of CD.  If I can find the dmg for the latest version of CD compatible with my Mac OSX, I will try a clean reinstallation.  Not sure what to do if that fails.

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  • moleculep heasant

    I am unable to upgrade to this version, and as I previously mentioned, this issue has plagued me for multiple CD versions.

    https://informatics-support.perkinelmer.com/hc/en-us/community/posts/7432028539028-1H-NMR-Prediction-yields-odd-results/backrooms game

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