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Topic: Identifying an organic compound  (Read 23003 times)

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Offline Paabo

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Re: Identifying an organic compound
« Reply #15 on: April 26, 2009, 06:13:47 PM »
Well, that was awfully mean. I thought I was supposed to come here with help on my organic work? All I asked was that you try to maybe simplify it for me. I'm not looking for you to do my work for me. It's just that after exhausting every resource which I was given (which wasn't much, I might add), I still keep arriving at 2,4-dichlorophenol. You can't even tell me, "Yes, you're right.", or, "No, you're wrong. Recheck _____."? I apologize that I'm not the amazing chemist you apparently are, looking down on everyone who can't decipher every bit of scientific jargon. Maybe one day, if I work real hard, I can be as much of an elitist as you.

Offline macman104

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Re: Identifying an organic compound
« Reply #16 on: April 26, 2009, 06:51:22 PM »
I think there was a miscommunication here.

Paabo meant by "jibberish" that it didn't make sense because he doesn't understand.  He didn't mean it was wrong, or incorrect, just asking for a re-explanation.

Paabo, what Squirmy was trying to explain was that your CNMR was run in CDCl3.  However, because your compound has aromatics, and CDCl3 absorbs at 7.26ppm in the HNMR, she may have switched it to Acetone-d6.  But regardless, those peaks at 2.0 are not part of your compound.

Also, if you ignore the fine-splitting (some special long-range splitting) that has occurred in the aromatic HNMR, you can deduce that you have a singlet, a doublet and a doublet.  So now try and verify that your structure would give rise to those types of splitting patterns.

Offline Paabo

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Re: Identifying an organic compound
« Reply #17 on: April 26, 2009, 06:53:56 PM »
Ah, okay! I get it now. This is very helpful. I'm sorry I snapped like that, squirmy. I'm under a massive amount of stress this semester, and even more so since finals are this week. Also, thank you macman for clearing that up for me. I should be able to figure this out now.

Offline Paabo

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Re: Identifying an organic compound
« Reply #18 on: April 26, 2009, 07:17:52 PM »
Gahh, so I'm wrong then, eh? If I had 2,4-dichlorophenol, there would be 3 peaks (2 in the aromatic ring, 1 on the O), all singlets, right? So then I'm back to the drawing board. I just don't understand how the CNMR and IR can be identical to that of 2,4-dichlorophenol, but have a different HNMR. I'm so confused.. Also, I realized that my professor has written "small peak ~13.8" on the HNMR. Did you guys take that into account?

Offline Squirmy

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Re: Identifying an organic compound
« Reply #19 on: April 26, 2009, 07:24:36 PM »
Was just thinking I might've read too much into the "gibberish" comment. Thanks for clearing things up, macman!

Apologies for my last post ;)  

Offline Paabo

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Re: Identifying an organic compound
« Reply #20 on: April 26, 2009, 07:38:18 PM »
Wait, I just realized everything I wrote in the last post was wrong. Stay tuned for more....

Offline Paabo

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Re: Identifying an organic compound
« Reply #21 on: April 26, 2009, 07:40:48 PM »
Okay, so 2,4 dichlorophenol WOULD account for the singlet and 2 doublets. But now what about the peak at 2.81 (is this not part of the molecule, like the mass at ~2?), and the peak at 13.8? I have no idea how to explain these.

Offline Squirmy

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Re: Identifying an organic compound
« Reply #22 on: April 26, 2009, 07:58:59 PM »
The peak at 13.8 is the one piece I wasn't too sure about. It's higher than normal for a phenol O-H, but maybe with hydrogen-bonding with acetone it could fit. (hydrogen bonding tends to shift an OH signal to higher ppm).  Again, I'm not too sure.

It's not that unusual for the phenol OH to not show up at all if there's water around. The hydrogens on water and the phenol can exchange.

The 13C NMR and IR are spot on for your assignment of 2,4-dichlorophenol, and the mp is close. Don't overstress the 1H NMR.

Offline Squirmy

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Re: Identifying an organic compound
« Reply #23 on: April 26, 2009, 08:01:08 PM »
2.8 is easy to explain --> water in acetone

Offline Paabo

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Re: Identifying an organic compound
« Reply #24 on: April 26, 2009, 08:04:55 PM »
Alright; it seems that if it ISN'T 2,4-dichlorophenol, I'm not going to figure out what it IS, since it looks so much like the compound. I'm just going to press forward with this one. Thanks a bunch for your help, guys. I couldn't have done it without you.

Offline sjb

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Re: Identifying an organic compound
« Reply #25 on: April 27, 2009, 04:43:56 AM »
Although without a list or similar, I doubt you'd really be able to tell the difference between, for instance 2,4-dichlorophenol and 2,4-dibromophenol.

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