科研之友
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摘要
Kinetic studies for the azo-coupling reactions of 3-ethoxythiophene 1 with a series of 4-X-substituted diazonium cations 2a-e (X = OCH3, CH3, H, Cl, and NO2) have been investigated in acetonitrile at 20 degrees C. The second-order rate constants have been employed to determine the nucleophilicity parameters N and s of the thiophene 1 according the Mayr equation. Thus, the nucleophile-specific parameters N and s of thiophene 1 have been derived and compared with the reactivities of other C-nucleophiles in acetonitrile (pyrroles, furan, indoles, etc.). The Yukawa-Tsuno plot resulted in an excellent correlation (R-2 = 0.9980) with an r value of 0.89, suggesting that the nonlinear Hammett plot observed in the present work is due to resonance demand of the -electron donor substituent of on the -N-2(+) moiety. Importantly, using the concept of global electrophilicity () proposed by Parr, we successfully predict the electrophilicity parameters E of seven substituted diazonium cations whose experimental data are available.
- 出版日期2016-5
