Substituent effects on the reactions of aromatic triflones with para-X-anilines in methanol: Low intrinsic reactivity and transition state imbalances
✍ Scribed by Nizar El Guesmi; Taoufik Boubaker
- Publisher
- John Wiley and Sons
- Year
- 2011
- Tongue
- English
- Weight
- 155 KB
- Volume
- 43
- Category
- Article
- ISSN
- 0538-8066
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✦ Synopsis
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 (Δ^≠^G), enthalpy (Δ^≠^H), and entropy (Δ^≠^S) of activation are examined. Aniline addition to triflone 1a is characterized by a β~X~=0.57, α~Z~=0.31, and an imbalance of I = α~Z~–β~X~=−0.26. The imbalance shows that resonance development lags behind CN bond formation at the transition state. Interestingly, analysis of the results in terms of Marcus theory reveals that these S~N~Ar are associated with some extremely low intrinsic reactivity (log k~o~=−1.25& © 2011 Wiley Peiodicals, Inc. Int J Chem Kinet 43: 255–262, 2011