1980 Volume 53 Issue 8 Pages 2348-2356
Trifluoroacetolysis rates and products were determined for eleven 4-(m- and p-substituted phenyl) butyl 6-methyl-2-naphthalenesulfonates. Most substrates solvolyze predominantly or even exclusively with aryl assisted (kΔ) pathway. Dissection of kΔ into Ar1-5 and Ar2-6 components was performed by means of quantitative 13C NMR study of suitably labeled p-methyl and p-fluoro derivatives; the results were 32.4% Ar1-5 and 67.6% Ar2-6 for the former and 43.3% Ar1-5 and 56.7% Ar2-6 for the latter. For other substrates the dissection was carried out by postulating two independent linear free energy relationships (LFER) for the two pathways determined by the above four partial rates. Ar2-6 is much prefered over Ar1-5 through the series; for the unsubstituted derivative 90.6% Ar2-6 vs. 9.4% Ar1-5 was determined. A completely different approach by means of non-linear regression analysis of kΔ as a sum of two independent LFER gave fairly different and rather unsettled results, limitations of such an approach being suggested. The characteristics of remote aryl participation are discussed based on the above data.
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