Studies of the ortho effect in fragmentations of acetyl ion adducts of disubstituted benzenes

The ion-molecule reactions of disubstituted benzenes under chemical ionizat ion conditions with acetyl chloride as reagent gas were examined, and the f ragmentation reactions of the adduct ions (mostly proton and acetyl ion add ucts) were studied by collision-induced dissociation. Electron-releasing su bstituents favored the adduct reactions, and electron-withdrawing groups di d not. The position and properties of substituting groups had an effect on the relative abundances of the adduct ions. Several examples of the ortho e ffect were observed. The fragmentation reaction of the adduct ions formed b y ortho-benzenediamine with the acetyl ion was similar to the reductive alk ylation reaction of amines in the condensed phase. Copyright (C) 2001 John Wiley & Sons, Ltd.