Mass spectrometry of aralkyl compounds with a functional group—IX: Hydrogen scrambling in the molecular ion of hydrocinnamaldehyde

The molecular ion of hydrocinnamaldehyde (C₆H₅CH₂CH₂CHO) chiefly loses fragments C₂H₂O and C₃H₄O. Mass spectra of specifically deuterated analogues show that in the loss of C₂H₂O an α-hydrogen atom (with respect to the aldehyde group) is transferred to the aromatic part. A shift of the aldehydic hydrogen to one of the ortho positions of the phenyl ring and loss of C₂H₂O by a McLafferty rearrangement is not observed. In the loss of C₃H₄O also an α-hydrogen atom migrates to the aromatic part. Both reactions appear to occur with an extensive randomization of all hydrogen atoms in the molecular ion.