I have a DEPT analysis problem.

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Discussion Overview

The discussion revolves around a DEPT (Distortionless Enhancement by Polarization Transfer) analysis problem related to NMR (Nuclear Magnetic Resonance) spectroscopy of an organic sample. Participants explore methods to differentiate between CH and CH2 peaks in the DEPT spectrum, which are expected to be distinct but appear similar in the participant's results.

Discussion Character

  • Exploratory, Technical explanation, Experimental/applied

Main Points Raised

  • One participant describes the issue of overlapping CH and CH2 peaks in the DEPT spectrum and seeks suggestions for separation.
  • Another participant references a Wikipedia article, suggesting that separation can be achieved by varying the tip angle of the final 1H pulse.
  • A third participant recommends performing experiments to determine the 90-degree pulse width for the CH proton and calculating the 45-degree pulse width, emphasizing the need for accuracy and appropriate pulse delays.
  • This participant also notes the importance of not having the proton decoupler on continuously during the acquisition of the FID (Free Induction Decay).

Areas of Agreement / Disagreement

Participants present various approaches and suggestions, but there is no consensus on a single method to resolve the issue of overlapping peaks. The discussion remains unresolved regarding the best approach to separate the CH and CH2 peaks.

Contextual Notes

Participants mention the need for accurate experimental setups and conditions, such as pulse width determination and pulse delays, but do not provide specific details on the assumptions or limitations of their proposed methods.

hyildirim
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I have taken a DEPT spectrum of an organic sample.
It has 4 spectras that are all protonated carbon, CH, CH2 and CH3.
They especially CH,CH2, and CH3 spectras should be different but CH and CH2 spectras are same.
What can I do to separate CH and CH2 peaks? Could you give me any suggestion?
 
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You will need to perform an experiment to determine the 90 degree pulse width for the CH proton and from that calculate the 45 degree pulse width. That needs to be fairly accurate and you need to put in a pulse delay 10X the longest decay constant for the slowest recovering proton... another experiment for that. Be sure the proton decoupler is not on continuously as well while you acquire the FID.
 
Thanks for your helps..
best regards
 

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