High-Level Systematic ab Initio Comparison of Carbon- and Silicon-Centered SN2 Reactions Attila Á. Dékány, Gyula Z. Kovács, and Gábor Czakó* MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary * E-mail: gczako@chem.u-szeged.hu 4 CH3- C -0.0000000191 0.0759287567 -0.0000003271 H 0.8866887870 -0.3015991802 -0.5351328055 H 0.0200965974 -0.3015977901 1.0354613979 H -0.9067851573 -0.3015992439 -0.5003246951