October 15, 2021, 04:24:43 PM
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Topic: Mass Spectrometry  (Read 575 times)

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Offline ying63

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Mass Spectrometry
« on: July 30, 2021, 02:18:10 AM »
Today at class we are asked to find the most common fragment of 1-Butanol from the Mass Spec graph. It has a base peak of 56, and while attempting to split the butanol, the closest molar mass that I could get was 57 (from removing the hydroxyl group). I tried to look for an explanation on the internet but couldn’t find any. What mistake have I made?

Thank you

Offline Orcio_Dojek

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Re: Mass Spectrometry
« Reply #1 on: July 30, 2021, 03:21:41 AM »
What mistake ? Probably in calculations as 74 - 56 = 18, so the leaving group must have the molar mass equal 18.

Offline ying63

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Re: Mass Spectrometry
« Reply #2 on: July 30, 2021, 03:33:16 AM »
I removed the OH which only has a molar mass of 17 from CH3CH2CH2CH2OH, however I don't think I could further remove an extra Hydrogen, since the Hydrogen is bonded with the carbon, not the OH group

Offline Orcio_Dojek

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Re: Mass Spectrometry
« Reply #3 on: July 30, 2021, 05:43:16 AM »
How then you explain mass of the main peak (56 u)?

Maybe it is that OH radical takes H from adjacent molecule?

After all HO-H is a stronger bond than aliphatic C-H.

Offline ying63

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Re: Mass Spectrometry
« Reply #4 on: July 30, 2021, 06:43:43 AM »
I think I understand now. Thanks :)

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