Reactivity and mechanism of 1-X-2-(O-nitrophenyl)ethanes in base induced beta-elimination reactions with formation of O-nitrostyrene

Studies of acid-base catalysis in acetohydraxamic/acetohydroxamate buffers, WD exchange and solvent isotope effect show that the mechanism of the beta -elimination with the formation of o-nitrostyrene from the N-[2-(o-Nitrophe nyl)ethyl] quinuclidinium ion (1) is E(1)cb, involving an intermediate carb anion formed with a high degree of reversibility. The reactivity of 1-X-2-o-nitrophenylethanes with various leaving groups su ch Br, Cl, F, quinuclidine, and tetrahydrothiophene in OH./H2O is reported. At 25 degrees C in OH-/H2O, mu = 1 M KCl, the second order rate constant f or the elimination reaction from (1) is k(OH) = 4.9 . 10(-5) M-1 s(-1) and it is 15.7 times lower than that of the corresponding p-nitro substituted a nalogue [1] (k(OH) = 0.77 . 10(-3) M-1 s(-1)).