The Rates of SN2 Reactions and Their Relation to Molecular and Solvent Properties

✍ Scribed by Luis G. Arnaut; Sebastião J. Formosinho

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 198 KB
• Volume: 13
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200700276

✦ Synopsis

Abstract

The energy barriers of symmetrical methyl exchanges in the gas phase have been calculated with the reaction path of the intersecting/interacting‐state model (ISM). Reactive bond lengths increase down a column of the Periodic Table and compensate for the decrease in the force constants, which explains the near constancy of the intrinsic barriers in the following series of nucleophiles: F^−^≈Cl^−^≈Br^−^≈I^−^. This compensation is absent along the rows of the Periodic Table and the trend in the reactivity is dominated by the increase in the electrophilicity index of the nucleophile in the series CN2 and electron‐transfer mechanisms is clarified and it is shown that smaller solvent static effects should be expected for electron transfer in the absence of a thermodynamic driving force.