Lesson 1
Predicting Relative Rate Constants – The Hammond Postulate 1
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Prof. McBride, J. Michael, CHEM 125b, Freshman Organic Chemistry II, Spring 2011, YALE Open Courses: Yale University, Chemistry (Accessed 14/09/2014), http://oyc.yale.edu/chemistry/chem-125b/lecture-2 License: Creative Commons BY-NC-SA Curious kinetic orders can be mechanistically informative. Fractional kinetic orders suggest dissociation of a dominant aggregate to give a smaller reactive species. An apparent negative kinetic order, due to competition with a second-order process, leads to spontaneous deracemization of chiral crystals. Changes in bond dissociation energies can be due to differences in bonds or in radicals. Hammond helped organic chemists begin to think systematically about predicting relative reaction rates by suggesting that the transition states of more exothermic reactions should lie closer to the starting materials in structure and energy.

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