[nonlinear]

So, I took a mass spec sample of 4-(benzyloxy) benzonitrile. The major peaks were at m/z = 91 and 65. I'm having a bit of trouble figuring out the m/z = 65 fragment-- I can't seem to think of anything that doesn't break the benzene ring. It seems wrong to break the benzene ring, since I know its aromaticity gives it lots of stability. I figured that since the mass is an odd number, the fragment must contain the nitrile group... but that's about as far as I've gotten. Can anybody help me out here? Thank you!

[orgopete]

Ah yes, it is difficult to predict/explain the chemistry of mass spectroscopy. It has been a while since I have looked at a specialized book on MS. From my recollection, it takes atom labeling in order to actually identify the chemistry that actually might be taking place. Although benzene itself does show its base and parent without fragmentation, there are smaller fragments. If you want to identify possible fragments, I suggest you begin with one of these MS books in which aromatic fragmentation has been studied.

[Honclbrif]

I'd start with something like Spectrometric Identification of Organic Compounds by Silverstein et al. Its a pretty good general textbook for organic spectroscopy and I think the MS fragmentation section was pretty complete and well explained.