Secondary alpha-deuterium kinetic isotope effects: assumptions simplifying interpretations of mechanisms of solvolyses of secondary alkyl sulfonates.
For solvolyses of 2-propyl and cyclopentyl sulfonates, logarithms of alpha-deuterium kinetic isotope effects (alpha-KIE) correlate linearly with logarithms of nucleophilic solvent assistance (NSA); correlations have the same slopes, but different intercepts, consistent with both solvent and structural effects on alpha-KIEs for heterolysis, further supported by recent theoretical and experimental data. It is argued that alpha- and beta-KIEs cannot yet distinguish between mechanisms proceeding via one or more transition states of similar energies. Structural, solvent, and isotope effects can be rationalized by heterolysis accompanied by NSA.
Bentley
T William
TW
Department of Chemistry, University of Wales, Swansea, Singleton Park, Swansea SA2 8PP, Wales, United Kingdom. cmsolvol@swansea.ac.uk