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1 H NMR of C5H8O2

1 H NMR of C5H8O2 - Chemistry Forum

1 H NMR of C5H8O2 - Chemistry Forum. Discuss chemical reactions, chemistry.


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  #1  
Old 11-14-2003, 05:28 AM
Daveman
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Default 1 H NMR of C5H8O2



Hi.
I am trying to come up with a structure for this molecule C5H8O2.

The 1 H NMR has 3 lines grouped around 1.0 ppm with area of 3H, 6 lines
grouped near 1.9 ppm with area of 2H, and 3 lines grouped around 3.4 ppm
with an area of 2H.

The IR spectrum has a medium spike at 3000, a big spike at 1720, and a
medium spike at around 1640.

The NMR tells me that part of the molecule is probably CH3CH2CH2-, but what
about the rest?

I am sure I have a C=O. Do I also have C=C?

Any help would be greatly appreciated.

Dave


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  #2  
Old 11-14-2003, 05:37 AM
Barry Hunt
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Default 1 H NMR of C5H8O2


"Daveman" <[Only registered users see links. ]> wrote in message
news:tKZsb.109936$[Only registered users see links. ]. com...
what

How about a cyclopropane attached to -CH2-COOH?

Barry Hunt


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  #3  
Old 11-14-2003, 05:59 AM
Daveman
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Default 1 H NMR of C5H8O2

Thanks for your reply.

Will this work?

Are the hydrogens in the correct places to match the NMR?

Dave

"Barry Hunt" <[Only registered users see links. ].au> wrote in message
news:bp1pjn$4ca$[Only registered users see links. ].au...


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  #4  
Old 11-15-2003, 12:38 AM
Steve Turner
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Default 1 H NMR of C5H8O2

"Daveman" <[Only registered users see links. ]> wrote:


This interpretation is only capturing a small portion of the
information available from the spectrum. See comments from Richard
Shultz in another post. Your description of the three groups does not
include necessary information about the spacing, relative heights, and
overall appearance of these lines. For example, three lines can
belong to a triplet, or a doublet and a singlet, a doublet of
doublets, or a more complex pattern. The coupling constants can also
be useful in determining which pattern is coupled with which other
pattern(s).

Steve Turner

Real address contains worldnet instead of spamnet
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  #5  
Old 11-15-2003, 03:40 AM
Qi Wang
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Default 1 H NMR of C5H8O2

Have you possibly ignored a signal at around 10 ppm with the integration of
1 proton (could be even in lower field, i.e. >10 ppm)? If yes, then you've
probably got propyl formate(HCOOCH2CH2CH3), which should give exactly the
same pattern of proton signals in high field (triple for CH3, triple
for -O-CH2 and sextet for -CH2-) I would say the IR also matches this
structure.





what



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  #6  
Old 11-15-2003, 04:45 AM
Qi Wang
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Default 1 H NMR of C5H8O2

Sorry I just go too fast, the proposed structure is incorrect( one carbon
less than the formula), I would suggest:
to identify the "missing" proton in NMR. If you got an aldehyde proton which
is usually at 10 ppm (normal sharp peak), then it could be an
alpha-ketoaldehyde; if no such proton exists, try to determeine if the
"missing" proton is a carboxylic one or hydroxylic one (very broad and low
signal at 11-12 ppm or anywhere from 1-5 ppm, but the integration can easily
find it out), then you could be closer to a solution.



of




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