[nexisrocks]

Hi,

I have an ¹H NMR spectrum, a ¹³C NMR spectrum and an IR spectrum, and from these I need to figure out what organic compound I have.  I've been trying to figure this out for several hours and still am unable to find an answer.  Please *delete me*  My lab is due Monday and, if at all possible, I need to know by tonight so I can actually write the report!

Please note that some of the peaks on the ¹H NMR and IR may be due to contamination from my other compound benzophenone.  However the contamination should be small and thus the peaks shouldn't be very strong.

My spectra are as follows:
¹³ NMR



IR



¹H NMR



I think I may have a para-substituted benzene ring, but for the life of me I can't figure out what the substituents could be.  The experimental melting point is 166-168C.  Thank you so very much for any help you can give me!
Shayla

[Sam (NG)]

Is this from an experiment that you did in Labs? What reactants did you use?

[nexisrocks]

The compound was given to me in a mixture - the goal of the experiment is to determine the structure of both compounds in the mixture.  I separated them through column chromatography, and then did chemical tests to determine functional groups.  Unfortunately, I don't trust my results for the tests as I was rushed and am not sure I did them properly, or that my equipment was properly cleaned.

My results were: no N, no S, no halogens.  No ketone or aldehyde.

However, I don't trust these.  Also, the peak at ~3300 on the IR spectrum leads me to believe that there may, possibly be an N-H stretch.

Shayla

[Sam (NG)]

I think it's virtually impossible to identify this compound from the data you have, i would want at least an MS, and some DEPT experiments would help too.  I've not got my spectroscopy text books with me so i can't look up what the peaks for 13C NMR mean.  What do the Singlet, Doublet etc labels stand for on the 13C spectrum?  Is that C-C coupling or C-H coupling?  I thought that 13C NMR was usually decoupled.  I'm not particularly sure how you are meant to assess the number of C atoms in the compound without appropriate mass data, hopefully somebody can enlighten me to this.  Even in 3rd year undergrad labs they provided us with the structure and just asked us to identify the peaks in spectra.

Despite these facts i would guess (and it is a guess) at the following:
168.26- Carbonyl

137-116- Benzene ring


Maybe it's an ester?  I'm not too sure at all, definitely don't take my word for it.

[nexisrocks]

As far as I know, the singlet/doublet/etc labels on the spectra refer to C-H coupling.  I've been doing some further searching, and I found a compound - N-(4-bromophenyl)acetamide - which matches the ¹³C spectra extremely well.  A breakdown of that is here: http://nmrshiftdb.ice.mpg.de/portal/js_pane/P-Results;jsessionid=B5B589D6E2B70326F19FD9CE54BD0237.tomcat1?startMolecule=0&spectrumType=All&nmrshiftdbaction=showDetails&molNumber=3

(although Carbon 8 does not have the Cl attached and is, instead, a CH₃).  This compound does, also, match your guesses for chemical shifts.

However, the ¹H NMR spectra for this compound only has two peaks, and the spectra I obtained has four peaks (though the TA only integrated three of them, which leads me to believe the fourth is not relevant/is an impurity).

Any ideas on why this might be, or a similar structure that might fit the ¹³C and the ¹NMR spectra?  I've been working on it, but as of yet have not found anything.

Thanks!
Shayla

[Sam (NG)]

The only thing that worries me is that for a halogenated compound, you would expect an IR peak in the sub 1000 region, and i can't see the scale, but i think that might be missing.  If it was OH, then this compound could be Paracetamol:



Several problems with this though, no OH peak in the IR, and no N-H peak in the proton NMR.