P.S. And if protonation is the problem then it is worth trying to neutralize
the acid in the CDCl3 using, for example, Na2CO3. This can be done separately
before hand using the CDCl3 to make up the NMR sample or to filter the NMR
solution into the NMR tube using a Pasteur pipette plugged with a bit of
rolled up tissue paper for the bed of Na2CO3 to sit on.
Good luck and let us know what was successful.
K. Klika
________________________________________
> From: Muhammad Adil Raees via groups.io
> Sent: 01 October 2025 17:38:00
> To: main_at_ammrl.groups.io
> Subject: [AMMRL] Help Needed: Broad/Missing ¹³C NMR Signals
Hi all,
I’m seeking advice on improving ¹³C NMR spectra that show
broad or missing signals.
Sample KB-P19-NO₂ in CDCl₃ had broad/missing signals, but in
DMSO it became sharp with good intensity.
Sample HY-VI-135-HH in CDCl₃ is also showing broad/missing signals
and is insoluble in Acetone, DMSO, and MeOD. We specifically want to improve
the ¹³C signals for HY-VI-135-HH.
For these experiments, I used zgpg or zgpg30 pulse programs. NMR instrument
is working fine — standard tests in CDCl₃ (ethyl benzene)
show all signals clearly. The FID files and molecular structures are attached
for reference.
It seems sample-related, but I’m wondering:
1. Could the broad signals be due to acquisition parameters?
2. Are there ways to improve the signals for HY-VI-135-HH?
3. Could the broadening be inherent to the molecule’s chemistry?
Any tips or shared experience would be greatly appreciated!
Thanks,
--
Muhammad Adil Raees, Ph.D.
Manager NMR Facility
The Central Laboratory
Syed Babar Ali School of Sciences and Engineering
Lahore University of Management Sciences
Opposite Sector-U, D.H.A. 54792, Lahore
+92-330-2866755
adil.raees_at_lums.edu.pk
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Received on Wed Oct 01 2025 - 08:18:44 MST