27 May 2008
Prof. Wes Borden (University of North Texas, Denton, TX, USA)
Theoretical Studies of the Schizophrenic Effects of Geminal Fluorination on Organic Reactions: Explanations and Predictions
Experiments by Dolbier and coworkers have found that geminal fluorination has a large effect on lowering the barrier to cis–trans isomerization of 1,2-dimethylcyclopropane and an even larger effect on lowering the barrier to racemization of optically active 1-ethyl-2-methylcyclopropane. In contrast, Dolbier has found that geminal fluorination has almost no effect on the barrier to rearrangement of methylenecyclopropane; and Lemal and coworkers have shown that geminal fluorination actually stabilizes [2.2.2]propellane toward ring opening and bicyclo[2.2.0]hex-1(4)-ene toward dimerization. In order to understand these very different effects of geminal fluorination, ab initio calculations have been performed and, from the results, explanations proposed and experimentally testable predictions made.