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Stochastic Search for Isomers of the sec-Butyl Cation
Valerije Vrček1, Olga Kronja1, Martin Saunders1
1Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1, 10000 Zagreb, Croatia, and Department of Chemistry, Yale University, New Haven, Connecticut 06520.
Abstract:
A stochastic search procedure for locating energy minimum structures was applied to the sec-butyl cation. A previously unreported structure 3' with strong H-hyperconjugative stabilization of the carbocation center was found at several levels of theory (HF, B3LYP, and MP2). The theoretical equilibrium isotope effect (EIE) for the monodeutero isotopomer of 3' (Keq = 1.4; t = -130 °C) indicates that the new structure is likely to be largely responsible for the experimentally observed EIE.
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