[Babcock_Hall]

We synthesized a simple sulfonyl ketone which gave good NMR data.  When we ran LC-MS (ESI), we saw a peak at M+20.  The paper upon which our synthesis is based used EI.  I thought about hydration of the ketone, but that did not seem to explain it.  Maybe an adduct of some kind?

[rolnor]

If both carbon and proton-NMR is OK I would not worry. Is this a new set of compounds? Ketones?

[Babcock_Hall]

If a reviewer is OK with the result, then I will not worry further.

[MOTOBALL]

Can you post a photo of the mass spectrum in the molecular ion region?
Say Mol. Wt plus/minus 50 amu.

Regards,
Motoball

[Babcock_Hall]

The software is a bit unfriendly, and this will take some time, but I will try.

[MOTOBALL]

Don't spend long on it.

A hand-drawn sketch would be ok, as long as the relative peak intensities are about right.

Motoball

[Babcock_Hall]

The first numbers are the values of m/z.  The second numbers are the percentages of the base peaks are indicated by the second number.

[Babcock_Hall]

In the negative chemical ionization mode, there is a peak at M-1 and also one at M+15.  A signal at M-1 makes sense in that sulfonyl ketones are acidic (pK_a ~11).

[MOTOBALL]

Your LC/MS ESI +ve spectrum that you have posted seems to be composed mainly of adduct ions etc.

(1) What was the sample diluent, and what was the mobile phase?

(2) Was the Chem Ion. -ve ion mode run in CH4 ??

(3) Could you have your MS person printout a background-subtracted list of m/z 150 - 500, so that we can get an idea of the relative intensities of the 12C, 1H, 14N, 32S ions at 168, 210, 218, 279, 317 etc versus their 13C, 2H, 34S isotopic peaks.

Thank you!

Motoball

[Babcock_Hall]

Samples were diluted in acetonitrile, and the gradient was a rising concentration of acetonitrile in water.  I will have to get back to you on ionization.  If I understand correctly, our software/instrument was designed for maximum possible compliance with GLP or GMP.  We are not even supposed to use flash drives on the computer.  We are constrained to use screenshots of the chromatogram.  However, it may be possible to get some peak intensities; I will work on this.

[MOTOBALL]

Thanks for that info!

A screen shot to show relative intensity of the isotopic peaks would be good—- you don’t want to waste your time doing hand listings with a calculator.

Also, your negative ion CI spec with [M-H] at m/z 197 seems to confirm the MW.
I was just looking over the LC/MS data for interest.

Regards,
Motoball

[MOTOBALL]

Mr. Hall,

MW =198 requires N atom count = even (0, 2, 4,...etc).   

Does your molecule meet this spec?

With -SO2- and >C=O groups your molecule has some polarity and may well be solvated; I wonder if [M+H]+(H2O)2(MeCN)2 = m/z 317 is true.

The reviewer may note that there is a 38 amu difference between m/z 317 and m/z 279, and suggest that these are [M+K]+ and [M+H]+, respectively, of some unknown compound.

Regards,

Motoball

[Babcock_Hall]

I had forgotten that these spectra were obtained using ESI.  There are 0 nitrogen atoms in our molecule.  In a high-resolution experiment in negative mode, there was a large peak near 197 (presumed M-1) and a smaller one near 198.  The mass of the presumed molecular ion was 198.0297, which is about 52 ppm different from the expected value.

[MOTOBALL]

Mr. Hall,

Now that I'm learning more about your molecule (and possibly getting close to an empirical CHOS formula) is there any info that you wish to keep confidential or proprietary???

Regards,
Motoball
[My daughter did her undergrad at Madison, and I remember walking past Bascom Hall when we used to visit; from your user name are/were you at UWISC?]

[Babcock_Hall]

The compound we made is methylsulfonylacetophenone, C₉H₁₀O₃S.  Its exact mass is 198.035067.