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Author Topic: What is my unknown compound?  (Read 2877 times)

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mjoa123

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What is my unknown compound?
« on: December 05, 2012, 03:09:36 PM »

In lab we had to do tests in order to find out what our compounds are, but I have no idea where to even start. Is anyone good with this stuff?

My compound only contains H, C, and O. It is a clear liquid (basically looks like water). The boiling point is around 94° C. The refractive index is 1.38 nD. It is not soluble in water, HCl, or NaOH. It is soluble in chloroform.

I also ran NMR test and an IR spectrum. It is hard to describe the IR spectrum, but if needed I will.

The NMR had these peaks:

-Three peaks at: 4.0408, 4.0239, 4.0070
-One peak at: 2.0521
-Six peaks at (this is odd, but I asked and it can be correct, which might be a giveaway as to what my compound is?): 1.6965, 1.6778, 1.6605, 1.6422, 1.6249, 1.6067
-Three peaks at: 0.9627, 0.9441, 0.9255

Any help here? I am actually really quiet terrible in chemistry, unfortunately. Thanks.
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orgopete

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Re: What is my unknown compound?
« Reply #1 on: December 05, 2012, 06:05:40 PM »

If the three peaks at 0.9 ppm were a methyl group, then how many hydrogens are present on the carbon this memthyl group is attached? It is also very useful to give the integral for the peaks. You can virtually determine the molecular formula from the NMR & IR.
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mjoa123

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Re: What is my unknown compound?
« Reply #2 on: December 06, 2012, 07:10:11 AM »

If the three peaks at 0.9 ppm were a methyl group, then how many hydrogens are present on the carbon this memthyl group is attached? It is also very useful to give the integral for the peaks. You can virtually determine the molecular formula from the NMR & IR.

Thanks for the help. I managed to take pictures of both the NMR and the IR spectrum. They are not the best pictures but hopefully they are legible.

NMR:

http://www.imagebam.com/image/c55f08224404309

IR spectrum:

http://www.imagebam.com/image/90a1b4224404313
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Arkcon

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Re: What is my unknown compound?
« Reply #3 on: December 06, 2012, 08:18:35 AM »

There's an additional options button on a posting page that allows you to attach images to this forum.  I would've done it for you, but the images don't appear in the Imagebam page.
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mjoa123

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Re: What is my unknown compound?
« Reply #4 on: December 06, 2012, 09:00:15 AM »

There's an additional options button on a posting page that allows you to attach images to this forum.  I would've done it for you, but the images don't appear in the Imagebam page.

You can't see the images when clicking on the links?

I did put the images with the "[ img ] [ / img ] (without the spaces)" but they didn't show up.
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discodermolide

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Re: What is my unknown compound?
« Reply #5 on: December 06, 2012, 09:36:46 AM »

The coupling pattern in the NMR should help you find out what this compound is.
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mjoa123

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Re: What is my unknown compound?
« Reply #6 on: December 06, 2012, 09:47:44 AM »

The coupling pattern in the NMR should help you find out what this compound is.

I posted the NMR in post #3, can you see it?
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discodermolide

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Re: What is my unknown compound?
« Reply #7 on: December 06, 2012, 09:51:27 AM »

I saw both spectra by clicking on the links you gave.
What do you know about coupling patterns in the NMR spectrum?
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mjoa123

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Re: What is my unknown compound?
« Reply #8 on: December 06, 2012, 09:59:45 AM »

I saw both spectra by clicking on the links you gave.
What do you know about coupling patterns in the NMR spectrum?

Pretty much nothing. I know that they took out water and chloroform from the graph. I think that the ppm tells the amount of each element but that it's not always accurate I believe. I looked for a guide that would match the numbers with an element so that I can maybe connect the puzzle but couldn't find anything. Have no clue  :-\
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discodermolide

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Re: What is my unknown compound?
« Reply #9 on: December 06, 2012, 10:03:43 AM »

ppm in this case refers to the chemical shift references to TMS (tetramethylsilane) which is 0.
Have a look here
http://en.wikipedia.org/wiki/Proton_NMR

I can't teach you about H-NMR here, so you will have to start perhaps with that web page.
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mjoa123

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Re: What is my unknown compound?
« Reply #10 on: December 06, 2012, 10:16:58 AM »

ppm in this case refers to the chemical shift references to TMS (tetramethylsilane) which is 0.
Have a look here
http://en.wikipedia.org/wiki/Proton_NMR

I can't teach you about H-NMR here, so you will have to start perhaps with that web page.

How do I know if the lines are an H, C, or an O?
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discodermolide

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Re: What is my unknown compound?
« Reply #11 on: December 06, 2012, 10:21:05 AM »

The signals in the spectrum correspond to the hydrogens in the molecule. The position gives you information at to its chemical environment. The number of lines tells you how many hydrogens are on the adjacent carbons.
So for example a CH3 group attached to an oxygen atom would appear at a different place to a CH3 group attached to another carbon atom.
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mjoa123

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Re: What is my unknown compound?
« Reply #12 on: December 06, 2012, 10:23:23 AM »

The signals in the spectrum correspond to the hydrogens in the molecule. The position gives you information at to its chemical environment. The number of lines tells you how many hydrogens are on the adjacent carbons.
So for example a CH3 group attached to an oxygen atom would appear at a different place to a CH3 group attached to another carbon atom.

So the first 3 lines means there are 3 hydrogen atoms attached to either an oxygen or carbon? The the huge line means one hydrogen attached in the middle, then what about the 6 lines?

And is there a way to know if it's attached to an oxygen or carbon atom?
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discodermolide

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Re: What is my unknown compound?
« Reply #13 on: December 06, 2012, 10:29:22 AM »

The numbers under the lines in the spectrum tell you how many hydrogens are sitting on the carbon, although in your example they look a little off to me.
In the link I provided there is a table of chemical shifts. Use that to decide if it is attached to an oxygen atom or something else.
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mjoa123

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Re: What is my unknown compound?
« Reply #14 on: December 06, 2012, 10:34:29 AM »

The numbers under the lines in the spectrum tell you how many hydrogens are sitting on the carbon, although in your example they look a little off to me.
In the link I provided there is a table of chemical shifts. Use that to decide if it is attached to an oxygen atom or something else.

So there are 4 Hydrogens attached to the carbon, or 2.70 (aka 3)? And what does the number of lines mean then?
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