Participation by neighboring aryl groups. V. Determination of assisted and nonassisted rates in primary systems. Rate-product correlations

Rearrangement Studies with 14C. XXXVI. Solvolysis of 1-14C-2-Phenylethyl Tosylate in Aqueous Acetic Acid with or without Added Sodium Azide

“…The acetolysis of 1-14C-2-phenylethyl tosylate (1-OTs-1-14C) has been extensively investigated (1 and references given therein) and the results have generally been attributed to two competing processes, namely, a direct displacement (solvent assisted or k, pathway) and reaction via the ethylenephenonium ion (2) (anchimerically assisted or k, pathway) (1)(2)(3). On the other hand, the work of Sneen and Larsen (4,5) suggested the possibility that such solvolyses could proceed solely through an ion-pair mechanism.…”

Hammett ρ+ Values as Kinetic Evidence for the Concerted Biomimetic Bicyclization Mechanism

“…The values of ρ + obtained in both solvents (different nucleophilicity) are essentially the same, excluding the possibility that this extremely significant result is due to rate determining displacement by the solvent . All the results can be attributed to the relatively small partially positive charge on the benzylic carbon of the transition state, since the charge is delocalized on at least five carbon atoms in concerted bicyclization, as is shown in structure 7 .…”

Application of the ethanol-trifluoroethanol method to solvolyses for which nucleophilic involvement is questioned

“…The solvolysis of ring-substituted benzyl derivatives gives curved Hammett plots50 typical of those observed when there is a change of mechanism along a series. 51 Okamoto and Brown50 have interpreted these curved Hammett plots as showing a change from an Sn2 mechanism for the deactivated benzyl compounds to an SnI mechanism for the activated compounds. However, this need not be the case.…”