Gas phase ion chemistry is a broad field with many applications which encompasses
various branches of chemistry and physics. It is continually developing, with new
approaches to obtaining kinetic (Knighton and Grimsrud) and thermochemical
(McMahon; Dunbar) data under a wide variety of experimental conditions and with
new insights into the mechanisms of ion — molecule reactions (Gellene; Bartmess)
and the parameters which control them. It is becoming increasingly obvious that
progress on this mechanistic aspect is being considerably advanced by the availability
of structural information on the reactants, products and reaction intermediates
(Schreiner, Schaefer, and Schleyer). As our understanding develops, there is a
need for more detailed reaction studies. The effects of molecular orientation on
reactivity (Brooks and Harland) is a case in point.