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 5 CH2F2 F -0.0000001103 0.2370484409 -1.0979080304 C -0.0000000722 -0.5561369818 -0.0000030179 F -0.0000004741 0.2370487406 1.0979086143 H -0.9097049242 -1.1545060116 0.0000083404 H 0.9097167993 -1.1544885972 0.0000166157 5 CH2Cl2 Cl -0.0000000682 0.1772588406 -1.4680901869 C -0.0000001983 -0.8086881692 -0.0000038418 Cl -0.0000001436 0.1772585374 1.4680909625 H -0.8968945782 -1.4165356850 0.0000070787 H 0.8969043909 -1.4165208460 0.0000114194 5 CH2Br2 Br -0.0000000025 0.0928384609 -1.6083371862 C -0.0000000609 -0.9710085270 -0.0000727575 Br -0.0000000069 0.0928362319 1.6083432939 H -0.8985720755 -1.5741855224 0.0001911007 H 0.8985735426 -1.5741836604 0.0001917219 5 CH2I2 I 0.0000000006 0.0649056606 -1.7985800587 C 0.0000000187 -1.0873433994 0.0001879406 I 0.0000000017 0.0649203956 1.7985588570 H -0.8965097493 -1.6943197543 0.0002150619 H 0.8965092369 -1.6943204738 0.0002147749 5 CH2FCl F -0.3372737745 -0.0000001230 -1.5200025800 C 0.6319097017 -0.0000001260 -0.5649262807 Cl -0.1031093638 -0.0000001519 1.0435598392 H 1.2269306267 -0.9031972879 -0.6619362045 H 1.2269177553 0.9032064504 -0.6619281566 5 CH2FBr F -0.3697854331 -0.0000000316 -2.0204621252 C 0.6530243445 -0.0000000942 -1.1254195229 Br -0.0415112855 -0.0000000392 0.6809519819 H 1.2395486167 -0.9052701786 -1.2440352916 H 1.2395424371 0.9052750019 -1.2440290514 5 CH2FI F -0.3936534029 -0.0000000649 -2.3721737283 C 0.6625048070 -0.0000000481 -1.5113950274 I -0.0235711149 -0.0000000089 0.5243813357 H 1.2464763322 -0.9042947806 -1.6498734160 H 1.2464721709 0.9042976970 -1.6498716130 5 CH2ClBr Cl -0.0000000408 0.2091906337 -2.0492929093 C -0.0000001268 -0.8750416748 -0.6587590056 Br -0.0000000351 0.0760204283 1.0255934979 H -0.8984888340 -1.4785874508 -0.6860974419 H 0.8984945603 -1.4785789295 -0.6860942810 5 CH2ClI Cl -0.0000000154 0.2328839304 -2.4563183734 C -0.0000000480 -0.9084258586 -1.1107269053 I -0.0000000080 0.0449443590 0.8097911698 H -0.8972956824 -1.5124987893 -1.1618140166 H 0.8972977998 -1.5124956083 -1.1618125534 5 CH2BrI Br -0.0000000108 0.1057840855 -2.0579728209 C -0.0000001039 -1.0239431495 -0.4934585073 I -0.0000000078 0.0561683099 1.3506944936 H -0.8978580034 -1.6281011781 -0.5175085743 H 0.8978610827 -1.6280968438 -0.5175079700