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Colloquia with Prof. G.B. Hammond, University of Louisville

"Does pixie dust exist? Rethinking the role of counterions in ionic chemical reactions"

Chemical reactions are enabled (or made more efficient) when the
appropriate catalyst is found, but a good catalyst almost always needs the right ligand, and
even when the best catalyst-ligand combination is found, it will still need the right
combination of additive, solvent or temperature. In other words, every reaction
is its own drama queen. Perhaps the notorious particularity of chemical reactions is the
reason why organic chemistry is (dis)regarded as an empirical science in some circles.

Recently, we asked ourselves the question: can we find a (quasi-)universal
reaction promoter that is capable of improving the efficiency of all, or most, ionic reactions
without modifying the original reaction conditions without having to reformulate
each one the thousand of ionic reactions known. We believe the answer to this question
lies on understanding the role of the counterion. In theory, the reactivity of a paired
working ion is lower than the corresponding ‘free’ working ion (we define the working
ion as the one directly involved in the reaction center). However, there are no
quantitative or mathematical treatments that predict the effect of ion pairing on
a reaction slowdown. In most theoretical and experimental studies of ionic
reactions, counterions are simply ignored. This presentation will describe the synthetic
implications of revisiting the influence of counterions in ionic reactions.

Mon Mar 31, 2014 4:15pm – 5:30pm Central Time
5211 SC (map)