Posts Tagged ‘lower free energy barrier’

Hidden intermediates in the (acid catalysed) ring opening of propene epoxide.

Monday, May 6th, 2013
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In a previous post on the topic, I remarked how the regiospecific ethanolysis of propene epoxide[1] could be quickly and simply rationalised by inspecting the localized NBO orbital calculated for either the neutral or the protonated epoxide. This is an application of Hammond’s postulate[[2] in extrapolating the properties of a reactant to its reaction transition state. This approach implies that for acid-catalysed hydrolysis, the fully protonated epoxide is a good model for the subsequent transition state. But is this true? Can this postulate be tested? Here goes.

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References

  1. H.C. Chitwood, and B.T. Freure, "The Reaction of Propylene Oxide with Alcohols", Journal of the American Chemical Society, vol. 68, pp. 680-683, 1946. http://dx.doi.org/10.1021/ja01208a047
  2. G.S. Hammond, "A Correlation of Reaction Rates", Journal of the American Chemical Society, vol. 77, pp. 334-338, 1955. http://dx.doi.org/10.1021/ja01607a027