Kinetic investigation of β-phenylethyl arenesulfonates with pyridine in acetonitrile revealed that the rates of these reactions which were lower than those of the reaction of benzyl benzenesulfonate with pyridine in acetone were increased with raising temperatures and pressures. The activation volumes were comparable to those of benzyl system, but activation entropies were negatively larger than those of benzyl system. From these phenomena it can be deduced that phenethyl system has more SN2 character in the transition state, comparing with the reaction of benzyl system. With raising pressures the Hammett reaction parameters (ρ) were decreased, indicating that the reaction is probably closer to tight SN2 character at higher pressures.
β-苯乙基芳
磺酸酯与
吡啶在
乙腈中的动力学研究表明,这些反应的速率低于
苄基苯磺酸酯与
吡啶在
丙酮中的反应速率,但随着温度和压力的升高,反应速率增加。活化体积与苄基系统相当,但活化熵为负值且大于苄基系统。由此可推断,相比之下,苯乙基系统在过渡态中具有更多的SN2特性。随着压力的升高,Hammett反应参数(ρ)减小,表明在较高压力下反应可能更接近紧密SN2特性。