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Topic: NMR help, part 2  (Read 6462 times)

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Garneck

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NMR help, part 2
« on: May 21, 2005, 03:14:14 PM »
Hi!

I have a bad day with NMR spectra today. I offered to help my girlfriend with her spectrum analysis and now I have to help interpret one that belongs her friend.

I'm so confused on this one. All I can say is that the shift at 4.3 ppm is from an NH2- gruop connected to a benzene ring. What those sextets are - I really have no idea. And the signal at 7.2 is a mysery to me, because it has no integral and it's neither a methoxy grop or a hydroxyl group.

This is, hopefully, the last time I'm bothering you with these spectras. Thanks in advance!
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dexangeles

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Re:NMR help, part 2
« Reply #1 on: May 21, 2005, 04:11:33 PM »
determining a compound is usually hard with H NMR alone.  Is thatall they're given for information?
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Garneck

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Re:NMR help, part 2
« Reply #2 on: May 21, 2005, 04:44:14 PM »
Quote from: Ad Majorem Dei Gloriam on May 21, 2005, 04:11:33 PM
determining a compound is usually hard with H NMR alone.  Is thatall they're given for information?

Yeah, well that's the problem - they didn't get anything else. Besides doing a functional analysis - this is supposed to be an aromatic amine and it has a chlorine atom - they didn't get any other info.

And I'm totally stuck on those two sextets  :-\
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Offline Winga

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Re:NMR help, part 2
« Reply #3 on: May 21, 2005, 04:56:44 PM »
Only a spectrum?
Any other information? e.g. molecular formula
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Offline Dude

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Re:NMR help, part 2
« Reply #4 on: May 21, 2005, 04:57:02 PM »
peak at 7.24 is likely residual chloroform from the deuterated solvent.  With the limited information, I would initially guess 4-chloroaniline since there are only two peaks (must be symmetrical).
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Garneck

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Re:NMR help, part 2
« Reply #5 on: May 21, 2005, 05:04:13 PM »
Quote from: Winga on May 21, 2005, 04:56:44 PM
Only a spectrum?
Any other information? e.g. molecular formula

Yes sir, only a spectrum.

Quote from: Dude on May 21, 2005, 04:57:02 PM
peak at 7.24 is likely residual chloroform from the deuterated solvent.  With the limited information, I would initially guess 4-chloroaniline since there are only two peaks (must be symmetrical).

Ok, but p-chloroaniline wouldn't give two sextets, now would it?
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Offline Winga

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Re:NMR help, part 2
« Reply #6 on: May 21, 2005, 05:59:11 PM »
The J-coupling, 4J is still greater than 0 in aromatic compounds.
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Offline movies

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Re:NMR help, part 2
« Reply #7 on: May 22, 2005, 01:58:05 PM »
I agree with Dude, looks like a p-substituted benzene ring.  The signal at ~7.2 is definitely CHCl3 from the NMR solvent.

The additional splitting you see could possibly be from coupling of the NH protons to the ring protons.  These couplings will be very small.
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