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Topic: Mass Spectrum of Hexanoic Acid  (Read 5416 times)

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Offline Robin97

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Mass Spectrum of Hexanoic Acid
« on: December 09, 2017, 11:37:14 AM »
I have to explain the fragmentation patterns of Hexanoic Acid, but i fail to do so.
, i found this Mass Spectrum of Hexanoic Acid online.
I know the peak at m/z=60 is due to a McLafferty fragmentation, but i can't really explain the peaks of m/z=87 and m/z=73.
Could someone please explain this to me?

Offline Babcock_Hall

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Re: Mass Spectrum of Hexanoic Acid
« Reply #1 on: December 09, 2017, 11:54:04 AM »
A good place to start is to determine how much mass M+• lost to make the those two fragments.

Offline Robin97

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Re: Mass Spectrum of Hexanoic Acid
« Reply #2 on: December 10, 2017, 08:30:07 AM »
Well according to the loss of the mass I would suggest a ethyl group is lost first (116-29=87) en then a methylene group is lost (87-14=73).
The problem is i can't really understand why that would happen, and what the mechanism is.
I always thought α-cleavages were more important if there is a carbonyl group present.

Offline Babcock_Hall

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Re: Mass Spectrum of Hexanoic Acid
« Reply #3 on: December 11, 2017, 08:53:36 AM »
I was a little surprised also, but I consulted Silverstein et al, 4th ed., and they briefly discuss hexanoic acid on page 27.

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