A combined experimental,theoretical, and Van't Hoff model study for identity methyl,proton, hydrogen atom,and hydride exchange reactions. Correlation with three‐center four‐, three‐, and two‐electron systems

We have studied carbon transfer reactions following an S_N2 reaction profile. With ab initio calculations and experimental geometries concerning the nature of the various complexes indicated as stable, intermediate, and transition state we were able to show the additional value of van't Hoff's tetrahedral configuration by changing its geometry via a trigonal pyramid into a trigonal bipyramid. The ratio of the apical bond and corresponding tetrahedral bond distances is then nearly 1.333. The relevance of this approach has also been shown for identity proton‐(hydrogen atom‐, and hydride‐) in‐line reactions. The use of this geometrical transmission will be demonstrated for the hydrogen bonding distances in e.g., DNA duplexes and other biological (supra) molecular systems. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008