Catalysis of the β-Elimination of HF from Isomeric 2-Fluoroethylpyridines and 1-Methyl-2-fluoroethylpyridinium Salts. Proton-Activating Factors and Methyl-Activating Factors as a Mechanistic Test To Distinguish between Concerted E2 and E1cb Irreversible Mechanisms
作者:Sergio Alunni、Valeria Laureti、Laura Ottavi、Renzo Ruzziconi
DOI:10.1021/jo020603o
日期:2003.2.1
Second-order rate constants, k(OH)(N), M(-)(1) s(-)(1), for the beta-elimination reactions of HF with 2-(2-fluoroethyl)pyridine (2), 3-(2-fluoroethyl)pyridine (3), and 4-(2-fluoroethyl)pyridine (4) in OH(-)/H(2)O, at 50 degrees C and mu = 1 M KCl, are = 0.646 x 10(-)(4) M(-)(1) s(-)(1), = 2.97 x 10(-)(6) M(-)(1) s(-)(1), and = 5.28 x 10(-)(4) M(-)(1) s(-)(1), respectively. When compared with the second-order
HF与2-(2-氟乙基)吡啶(2)的β-消除反应的二级速率常数k(OH)(N),M(-)(1)s(-)(1), 3-(2-氟乙基)吡啶(3)和4-(2-氟乙基)吡啶(4)在OH(-)/ H(2)O中于50摄氏度和mu = 1 M KCl时为0.646 x 10(-)(4)M(-)(1)s(-)(1)= 2.97 x 10(-)(6)M(-)(1)s(-)(1)和=分别为5.28 x 10(-)(4)M(-)(1)s(-)(1)。与氮甲基化底物1-甲基-2-(2-氟乙基)吡啶鎓碘化物(5)的相同工艺的二阶速率常数比较时,1-甲基-3-(2-氟乙基)吡啶鎓碘化物(5) 6)和1-甲基-4-(2-氟乙基)吡啶鎓碘化物(7),可以从比率k(OH)(NCH)3 /计算出甲基活化因子(MethylAF),值8.7使用基板5/2可获得x 10(5),具有6/3的值为1.6 x 10(3),具有7/4的值为2