[moun7]

Hello,

I've attached the question I need help on.



So, I'm asked to identify the mechanisms behind the 94 and 57 peak on the attached MS, the MS for the molecule above. The M+ peak is at 150. I've figured out the 57 peak but the 94 peak is giving me a lot of trouble. I believe it is due to some sort of rearrangement since the M+ peak and the 94 peak are both even. I've tried reasoning out a McLafferty rearrangement on the left side of the carbonyl, there is no gamma-H on the right side, so it is not possible there, but I'm not sure how that works since the gamma-H is part of the benzene ring.

Any help would be greatly appreciated.

Thanks

[moun7]

Update: I may have figured it out. I've attached where I'm at now. I have the right m/z but the arrow pushing felt wrong. Any input would be awesome.

[moun7]

Here's a better picture.

[moun7]

Another possible pathway.

[MOTOBALL]

4-Center mechanisms are very favored for re-arrangement mechanisms.

How can you draw a simple 4-center "ring" from the structure as shown ??