1987 Volume 60 Issue 3 Pages 1091-1095
The acetolysis rates of 2-arylethyl tosylates were determined for a series of aryl substituents. The non-linear substituent effect was reasonably accounted for on the basis of two linear LArSR relationships; one for the aryl-assisted (FkΔ) and one for the unassisted (ks) processes, respectively. A precise dissection of the apparent substituent effect into individual effects for both processes was achieved in this manner. The substituent effect on the ks process can be described as a linear function of σ° with a small ρs of −0.19, and that on the FkΔ process in terms of the LArSR Eq., with ρΔ=−3.87 and an rΔ=0.631. The use of σ+ for the FkΔ process failed to give any reasonable dissection. The r value for this FkΔ process is essentially identical to that for the neophyl solvolysis. The unique r value of 0.6 is concluded to be characteristic of β-arylassisted ionization processes in general.
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