A computational study of the role of hydrogen bonds in SN1 and E1 reactions

The reaction between tertiary butyl chloride and water clusters was examined by applying density functional theory calculations. The carbonium ion t-Bu(+) that is normally sandwiched between the water clusters was found to be absent, such that a Cbond;O covalent bond was formed in the intermediate (Int1) after heterolysis. An (H(2)O)(4) cluster is able to bridge the front and rear of the central carbon and promotes heterolysis. A correlation between bond interchanges at the central carbon and proton relays is presented. Stereochemical scrambling in the solvolysis products is discussed in terms of this correlation. In addition, an E1 pathway for the elimination product, iso-butene, is found from Int1.