I have to discuss the mass spectrum of diphenyl butadiene that I got from a wittig synthesis
I find very hard to discuss it because I've studied only the fragmentation of easy molecule (with 1 functional group)
Here I have 2 double bond and two phenyl all conjugated and I don't understand the possible fragmentation
I link the MS:
And here my doubts...
I can't do the classical fragmentation for aromatic ring, for example (because in benzylic position I have a double bond)
Also the molecular ion ...where is the positive charge? In the aromatic ring or in the C=C?? Could be located in both of them? (so different type of fragmentation)
-The 91 peak should be tropyliuml cation...bit I don't know the correct fragmentation in order to get it..
It need a benzylic -CH2 for the rearrangment (and in order to have 91 as m/z)but here I have only 1 H benzylic due to the C=C near the ring. Is a Hydrogen trasposition needed?
-I also see the loss of 1H atom from the molecular ion. Which Hydrgon is it? A H bonded to C=C or one bonded to the ring?