Is the collision induced loss of ethene from the (M – H+) ion of butyrophenone a γ-hydrogen rearrangement?

Abstract
The (M – H+) ion of butyrophenone undergoes the following reactions on collisional activation: losses of CH3, CH4, (C,H5), C2H4, C3H7, (CO + CH4), together with formation of C6H5 and C4H5O. Labelling studies (13C and 2H) show that the losses of CH3, C3H7 and the formation of C6H5 and C4H5O are specific and occur without hydrogen scrambling. All other reactions involve prior or accompanying hydrogen rearrangement. In particular, the loss of C2H4 is very complex: it involves loss of ethyl carbon atoms, but all hydrogen atoms are involved via specific rearrangement reactions. The phenyl–alkyl H rearrangements which are noted for this process occur after collisional activation of the (M – H+) ion.