I have to identify the structure of an unknown compound given a nmr, IR, and mass spectrum. I'm not sure how to analyze the mass spectrum and not completely sure about the nmr.

 

http://img.photobucket.com/albums/v31/PaperTigers/problem3pg1.jpg

http://img.photobucket.com/albums/v31/PaperTigers/problem3pg2.jpg

So what do you think do these spectra tell you?

From the NMR I got that it contains C4H12, I think. The IR shows a C-H stretch at 3000 and presence of methyl group. maybe C=O? From the mass spectrum all I could figure out was the molecular weight was 100 and it has a base peak at 57, but I don't understand how to interpret that.

Unfortunately I cannot see the spectra in the pictures properly. During interpretation of MS data you have to be careful to remember that the compounds are not necessarily single-charged (depending on compound and ionization method) and that they may fragment (again, dependent on ionization method).

After looking at it again I thought the compound was C5H12Si but it doesn't match up to the nmr, IR, or mass spectrum on

http://riodb01.ibase.aist.go.jp/sdbs/cgi-bin/direct_frame_top.cgi

 

From the mass peak at 57 I got C4H9. From the NMR there is a CH3. If you subtract the 57 from 100, the molecular weight of the compound from the mass spectrum, you get 28, which would indicate Si in the compound.

 

The NMR indicates a CH2 with a CH3 next to it, CH with CH6 next to it (2CH3?), CH6 with CH next to it, and CH3 with CH next to it.

 

The mass spectrum has its most intense peak at 57 and small ones at 56 and 58. small one at 71. peak 43 has intensity of 65. 29 has intensity 40. and various other small peaks at 27, 28, 39, 41, and 42.

 

The IR has sharp peaks at 3000 (aliphatic hydrogens), 1700, 1500-1400, and 1100-950.

 

I don't know if I'm interpreting these completely wrong or what.