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Topic: Relatively a Broad Singlet  (Read 3448 times)

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Offline Nescafe

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Relatively a Broad Singlet
« on: June 09, 2015, 08:49:36 AM »
Hi,

I have a peak that is a broad singlet at 1.78 (in CDCl3 and integrates to 1H). Now everything else makes sense on my molecule/H NMR except this, I have a NH on my molecule but I thought NHs do not show up and if they do they can be anywhere, but 1.78? is this not unusually up-field? if it helps the it is -CH2-NH-CH2- so next to two aliphatics.

Thanks in advance,

Nescafe.

Offline Babcock_Hall

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Re: Relatively a Broad Singlet
« Reply #1 on: June 09, 2015, 09:10:08 AM »
Somewhere I have a paper that gives the NMR shifts of various solvents in various NMR solvents.  Might be this:
J. Org. Chem. 1997, 62, 7512-7515
NMR Chemical Shifts of Trace Impurities: Common Laboratory Solvents,
Organics, and Gases in Deuterated Solvents Relevant to the
Organometallic Chemist
Gregory R. Fulmer,*,1 Alexander J. M. Miller,2 Nathaniel H. Sherden,2 Hugo E.
Gottlieb,3 Abraham Nudelman,3 Brian M. Stoltz,2 John E. Bercaw,2 and Karen I.
Goldberg

Offline Dan

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Re: Relatively a Broad Singlet
« Reply #2 on: June 09, 2015, 09:26:32 AM »
I have a NH on my molecule but I thought NHs do not show up and if they do they can be anywhere, but 1.78? is this not unusually up-field?

1.78 ppm for an aliphatic amine is perfectly plausible, I've seen them in this region before. Can you check for a COSY correlation to the flanking CH2s?

Add some methanol-d4 and see if it disappears.
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Offline pgk

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Re: Relatively a Broad Singlet
« Reply #3 on: June 09, 2015, 09:53:04 AM »
Dan is right. NH proton of alkylamines and cycloaliphatic amines may appear even at 0.5 ppm, depending on the sample concentration and the solvent. Besides, impurities do not often give an integration of 1H. However, a little drop of D2O also disappears the signal of the amine proton.
« Last Edit: June 09, 2015, 10:07:16 AM by pgk »

Offline Nescafe

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Re: Relatively a Broad Singlet
« Reply #4 on: June 09, 2015, 10:20:16 AM »
Great suggestions and comments guys, much appreciated

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