It has been asserted that, ‘kinetic studies, in one
guise or another, have historically made the greatest
contribution to the elucidation of reaction mechanisms’
[2]. Why is this so? The simple direct answer
is that the temperature dependence of the rate
constant reveals something about activated complex
structure. This is usually expressed in terms of the
activation parameters for the reaction. The enthalpy
of activation, ΔH≠, provides a reflection of the height
of the barrier to reaction while the entropy of
activation, ΔS≠, reflects the shape of the same barrier,
i.e., it reflects the relative order in the activated
complex (transition state energy level) vs. that in
reactants (ground state energy level).