[ReederJ]

First, I got this mass spectrum to analyse.



It asked me for:

1.) the m/z for the base peak
2.) the m/z for the molecular ion
3.) five possible molecular formulas that contain at least 4 carbons, only C, H, N, O, Br, and/or Cl, and no more than five unsaturations.

1 and 2 are labeled on the spectrum.

For number 3 I thought that there can be no Br or Cl because the molecular ion m/z isn't characteristic of them. Then I added up a bunch of formulas up to 98 and got the following:

C4H2O3
C5H6O2
C5H8ON
C6H10O
C6H12N
C7H14

Then I got this IR Spectrum.



I labelled how I interpreted it.

Here is where I start having major problems. The next problem says that both spectra are of the same molecule. It asks me to rule out some of my suggested molecules from the mass spectrum and draw three possible structures consistent with the possible formula(s) that remain(s).

I ruled out some, but when I tried to draw them I realized that I would probably need one of the spikes of the IR spectrum to be a C=C bond to give me all my unsaturations. I labeled where I thought that might be, but I can't find anything in my notes or the book that would suggest that spike is a C=C bond.

[dipesh747]

A C=C bond is 1680-1640 stretch. There will be some overlap with the C=O stretch. If you don't have access to IR absorption data use this http://wwwchem.csustan.edu/tutorials/infrared.htm

[ReederJ]

A C=C bond is 1680-1640 stretch. There will be some overlap with the C=O stretch. If you don't have access to IR absorption data use this http://wwwchem.csustan.edu/tutorials/infrared.htm

Thanks, I'm going to put that small spike around 1650 as my C=C bond and I think it should work out fine from there.

[orgopete]

I would start with the IR information and then look at your MS. If there is a C=O group, then it must be present in the parent ion, and either the base peak or the parent minus the base peak. That should go far in determining the number of carbons present in each. What kinds of MF have m/e 55? Go back to your IR, check the C=O frequency. What does it suggest? Is there a match in the MS?