2012 Volume 85 Issue 10 Pages 1112-1119
The denitrogenation reactions of fifteen differently substituted vinyl diazonium (ethenediazonium) ions were examined by MO method at MP2/6-31G*. The parent vinyl diazonium ion (1, CH2=CH–N2+) was shown to initially give the H-bridged cation via the anti-H migration transition state (TS) or the syn-H migration TS. The relative barrier for the two TSs is very small, being 1.0 kcal mol−1 favoring the anti-H migration TS in free energy. The primary open cation is located on a very shallow minimum, and is 4.4 kcal mol−1 less stable than the bridged cation in free energy. The reactions of Me- and Ph-substituted vinyl diazonium ions showed characteristic features depending on the substituent. Molecular dynamics simulations for the reactions of 1 revealed that trajectories from the reactant state mostly gave the bridged cation as expected from the MO result, but there were trajectories that directly led to the open cation without H-participation, a clear manifestation of a dynamics effect. A dynamics effect on the relative population of the bridged versus the open cation is also presented.
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