Yurkanis Bruice
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 NEW Organic Chemistry Bruice Paula Yurkanis  US $195.90
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I'm having trouble with Mass Spectrometry.
I'm gonna quote from Paula Yurkanis Bruice's Organic Chemistry textbook. I understood most of what I read, but in page 517 (Chapter 12, section 2) it reads: "Peaks (in a mass spectrum) are commonly observed at m/z values two units below the m/z values of the carbocations, because the carbocations can lose two hydrogen atoms."
CH3CH2CH2 -----------> CH2CH=CH2 H
(There's a positive symbol (carbocation) on the third carbon from left to right in the first stage (m/z =43, btw), and then another positive symbol on the first carbon from left to right in the second stage (m/z = 41). Plus a dot next to the H (radical).
It mustn't be that complicated, but I just can't visualize it. Thanks so much in advance!
Edit: Sorry, there's a plus (+) before the single Hydrogen. Please forgive the mess!
While I am unimpressed by the structural conversion, it does appear true. If you look at the mass spectrum of hexane (in SDBS), you will see the pattern described. Thus for several of the peaks, there is a corresponding peak two mass units less, the presumed loss of H2.
If you are wondering about my cynicism, search the SDBS database for alkanes CnH2n+2 with MS box checked. Look at the spectra and see how many compounds that you could identify from the MS and its fragmentation. I would argue you would have a better chance of matching your spectrum with the lit spectrum in SDBS than you will be able to see the patterns and rationalize structural information. The clue and information isn't wrong, but I think it is stretching an introduction to organic chemistry with this treatment.
