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Topic: Base peak for 1-phenyl-1-butanone  (Read 7761 times)

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Offline s30.93a

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Base peak for 1-phenyl-1-butanone
« on: January 26, 2017, 12:53:47 PM »
Mc Lafferty can occur for C=O or C=C, thus yielding 105 and 121 as two peaks, but which one will be base peak?

Offline MOTOBALL

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Re: Base peak for 1-phenyl-1-butanone
« Reply #1 on: January 26, 2017, 02:34:10 PM »
The base peak is that with the greatest relative intensity, so what determines rel int. Once an ion has been formed?

Offline s30.93a

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Re: Base peak for 1-phenyl-1-butanone
« Reply #2 on: January 26, 2017, 02:48:39 PM »
Obviously, the most stable cation will resemble base peak, if C=O will break its α-β bond -C-O+H will form, in other case -C-C+H will be formed. Please correct me if I'm wrong and thus the latter is preferred

Offline MOTOBALL

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Re: Base peak for 1-phenyl-1-butanone
« Reply #3 on: January 27, 2017, 03:00:34 PM »
Ionization of R1-CO-R2 will give R1-CO+ and R2-CO+
Which in your case will be more stable ?

Offline s30.93a

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Re: Base peak for 1-phenyl-1-butanone
« Reply #4 on: January 27, 2017, 04:13:17 PM »
Ionization of R1-CO-R2 will give R1-CO+ and R2-CO+
Which in your case will be more stable ?

I think it depends on the stability of the radical R2° or R1° as R-CO+ is stabilised by back bonding. please correct if i'm worng
I made these structures depending on Mc Lafferty, please tell which one will be base peak?

Offline MOTOBALL

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Re: Base peak for 1-phenyl-1-butanone
« Reply #5 on: January 27, 2017, 04:21:10 PM »
Ionization of R1-CO-R2 will give R1-CO+ and R2-CO+
Which in your case will be more stable ?

Offline MOTOBALL

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Re: Base peak for 1-phenyl-1-butanone
« Reply #6 on: January 27, 2017, 04:24:39 PM »
I don't believe that your drawn structure is 1-phenyl-1-butanone.
Please check !

Offline AWK

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Re: Base peak for 1-phenyl-1-butanone
« Reply #7 on: January 27, 2017, 07:57:21 PM »
Search NIST for MS of butyrophenon
AWK

Offline MOTOBALL

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Re: Base peak for 1-phenyl-1-butanone
« Reply #8 on: January 27, 2017, 11:21:14 PM »
Search NIST for MS of butyrophenon

AWK,
Why provide the answer on a platter, when our job is to help them think it through for themselves?

Offline AWK

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Re: Base peak for 1-phenyl-1-butanone
« Reply #9 on: January 27, 2017, 11:39:12 PM »
s30.93a discusses other compound (2-propyl-3,4-dihydro-2H-naphthalen-1-one). Two main peaks of butyrophenon are 105 and 77. Title of thread is incorrect.
AWK

Offline s30.93a

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Re: Base peak for 1-phenyl-1-butanone
« Reply #10 on: January 28, 2017, 08:03:12 AM »
No, i want to know base peak for both the compounds.
The latter which I posted has more possibilities for Mc Lafferty.
I want to know which of the fragmentation is preferred, thus I'll subsequently apply that fact to 1-phenyl-1-butanone

Offline s30.93a

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Re: Base peak for 1-phenyl-1-butanone
« Reply #11 on: January 28, 2017, 08:06:16 AM »
Search NIST for MS of butyrophenon

AWK,
Why provide the answer on a platter, when our job is to help them think it through for themselves?

I already knew such databases, but looking for reasons.

Offline AWK

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Re: Base peak for 1-phenyl-1-butanone
« Reply #12 on: January 28, 2017, 10:44:57 AM »
Then start from easier compound - butyrophenone. Show us McLafferty rearrangement
and two α-cleavages for this compound.
AWK

Offline s30.93a

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Re: Base peak for 1-phenyl-1-butanone
« Reply #13 on: February 01, 2017, 02:20:24 PM »
Then start from easier compound - butyrophenone. Show us McLafferty rearrangement
and two α-cleavages for this compound.

These are the two possible rearrangements.

Offline AWK

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Re: Base peak for 1-phenyl-1-butanone
« Reply #14 on: February 01, 2017, 02:27:05 PM »
These not give ions 105 and 77 which are most abundant in the spectrum of butyrophenone. Check α-cleavages.
AWK

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