Substituent Effect Studies of Aryl-Assisted Solvolyses. II. The Acetolysis of 2-Phenyl-2-(substituted phenyl)ethyl p-Toluenesulfonates

Article abstract of DOI:10.1246/bcsj.66.3021

The substituent effect on the acetolysis of 2-phenyl-2-(substituted phenyl)ethyl p-toluenesulfonates had a nonlinear LArSR correlation and was explicable in terms of a competitive aryl-assisted mechanism involving the X-substituted phenyl-assisted (k^X_M) pathway and the unsubstituted phenyl-assisted (k^X_N) pathway. By the application of the iterative nonlinear least-squares method based on the LArSR Eq., the substituent effect on the overall k_t was dissected into the best-fit k_M correlation of ρ_M=-3.53 with r_M=0.60, and the k_N correlation of ρ_N=-0.88 with ?⁰. The ρ_M and r_M values for the effects of assisting aryl substituents are quite close to those of the 2-methyl-2-phenylpropyl system and the small ρ_N value with unexalted ?⁰ constant for the unassisting aryls is compatible to the remote β-aryl effect. The relative rates of competing pathways dissected based on the substituent effect analysis agreed completely with the ratio of respective aryl migration products determined by the 13C-tracer method. Exact rate-product correlation demonstrates that this system involves two discrete aryl-assisted pathways, k^X_M and k^X_N, which do not cross over.