Abstract
A kinetic study is reported for S(N)A(r) reactions of 2,4,6-tris(trifluoromethanesulfonyl) anisole 1a with a series of para-X-substituted anilines 2a-e in a methanol solution at various temperatures. The substituent effects on free energy (Delta(not equal)G), enthalpy (Delta H-not equal), and entropy (Delta S-not equal) of activation are examined. Aniline addition to triflone 1a is characterized by a beta(X) = 0.57, alpha(Z) = 0.31, and an imbalance of I = alpha(Z)-beta(X) = -0.26. The imbalance shows that resonance development lags behind C-N bond formation at the transition state. Interestingly, analysis of the results in terms of Marcus theory reveals that these SNAr are associated with some extremely low intrinsic reactivity (log k(o) = -1.25). (C) 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 255-262, 2011