[Crystal1137]

I photobrominated 2,3-dimethylbutane and got some product...

The carbon-13 NMR spectra yielded the following ppm values (the x-axis values of the peaks): 77.5330,77.1131,76.6932,31.9882

The 1H-NMR spectra yielded the following ppm values (the x-axis values of the peaks): 7.9841,7.2562,4.0697,2.8162,2.2301,2.0809,2.0736,2.0690,2.0168,1.9664,1.9637,1.8007,0.8393,0.8182,-0.0059,-0.0077

So, to determine the identity of the compound, I was thinking that I could use this site: http://riodb01.ibase.aist.go.jp/sdbs/cgi-bin/direct_frame_top.cgi

However, for the 13C NMR Shift(ppm) and 1H NMR Shift(ppm), I tried putting the values above and got no hits.  What am I doing wrong?  Am I supposed to put in the x-values or y-values?

Thanks in advance!

[chronictonic]

do you have an HNMR data for your starting material? What purification have you attempted, as its likely to be a mixture given the number of peaks? Do you know what the proposed mechanism is? Have you excluded peaks which correspond to solvent impurities?

Sorry to answer a question with a stack of other questions but if you knew these things im sure it would all become obvious

[chronictonic]

 Maybe re-do the HNMR (since they're quick) just because its not calibrated right and it gives so many peaks (far too many)

[Crystal1137]

Reaction equation:



So bromine was reacted with an excess of 2,3-dimethylbutane in the presence of strong light.  The product was then cooled until a white precipitate formed, and this white precipitate was dissolved in deuterochloroform for NMR analysis.  The numbers I provided are all the x-values that are labeled on the NMR printout.  Nothing is excluded and not much purification has been attempted.  However, not all of the values correspond to big peaks.  There's really only one or two big peaks on the spectra.  Should I only input those into the database to search for the product?  I can also upload a copy of the NMR spectra if that helps...

Thanks.

[Dan]

What solvent are you using for your NMR sample? Because your ¹³C data looks like mostly CDCl₃ (triplet at 77).

Your sample may be too weak for ¹³C, try a more concentrated one.

I assume as you have simply listed every peak in the ¹H NMR and not attempted to identify splitting patterns or give integrals that you are not familiar with NMR. It's library time. Any general organic text will probably do, but I'd recommend these:

Introduction to organic spectroscopy - Harwood & Claridge

Organic spectroscopy - Kemp

Upload the spectra and we can probably help you out too - the info you've given so far is insufficient to solve the problem.

[Crystal1137]

What solvent are you using for your NMR sample? Because your ¹³C data looks like mostly CDCl₃ (triplet at 77).

Your sample may be too weak for ¹³C, try a more concentrated one.

I assume as you have simply listed every peak in the ¹H NMR and not attempted to identify splitting patterns or give integrals that you are not familiar with NMR. It's library time. Any general organic text will probably do, but I'd recommend these:

Introduction to organic spectroscopy - Harwood & Claridge

Organic spectroscopy - Kemp

Upload the spectra and we can probably help you out too - the info you've given so far is insufficient to solve the problem.

I cannot get a more concentrated sample at this point.  It is correct that we used CDCl3 for the solvent.  In the NMR tube, 5 cm was CDCl3 and 1 cm was the product.  I've attached the NMR spectra (clicking on it can make it bigger and complete I think):

1HNMR:


13CNMR:


Thanks for all your help !

[sjb]

I think there is more to the carbon NMR than is labelled, though it is still fairly weak. Is there a peak at about 73-4 ppm?

What does the fact that there only seems to be one major proton peak indicate?

[Crystal1137]

I think there is more to the carbon NMR than is labelled, though it is still fairly weak. Is there a peak at about 73-4 ppm?

What does the fact that there only seems to be one major proton peak indicate?

The graph shows a small peak, but it's not labeled, so I'm assuming that it's too weak to matter...

I'm not sure... the presence of CH2 groups?

[Crystal1137]

Could someone please help me with this?  Thanks.

[Dan]

Could someone please help me with this?  Thanks.

The problem is that you have not shown evidence of attempting to solve your problem (see forum rules). Having a single signal does not mean you have a CH₂ group - why would it? If you had read any material on NMR you would know this is nonsense. Are you just guessing until someone tells you the answer?

Open an organic chemistry textbook and look in the NMR chapter. Attempt the question again, post your answer and people will help you. I have suggested two texts already. Failing that there is always information online

[saliyana_85]

I think you should rerun your NMR. Your spectrum doesn't look good. There was only the solvent peak. Try  increase the sample to solvent ratio to get a clearer spectrum or purify your product first.