Retentive Solvolysis. 15. Salt Effect on the Retentive Phenolyses of 1-(<i>p</i>-Substituted phenyl)ethyl<i>p</i>-Nitrobenzoates. The Pattern of Salt Effect and the Number of Ion-Pair Intermediates in the S<sub>N</sub>1 Solvolysis
作者:Tomomi Kinoshita、Koichi Shibayama、Keizo Ikai、Kunio Okamoto
DOI:10.1246/bcsj.61.2917
日期:1988.8
The salt effect of sodium phenoxide on the polarimetric (kp) and titrimetric rate constants (kt) has exhibited pattern B for the phenolysis of optically active 1-(p-methylphenyl)ethyl p-nitrobenzoate (ROPNB; (1)) in pure phenol. The other patterns A, C, and D were previously observed for the phenolyses of 1-phenylethyl p-nitrobenzoates with p-MeO- (2), p-H- (3), and p-NO2-substituents (4), respectively. Thus, the kp–kt pattern changes in the order A→B→C→D as the stability of the intermediate decreases in the order of 2>1>3>4. All the kp–kt patterns can be correlated with the ion-pair stage for product formation, i.e., the pattern A with the second ion-pair intermediate and the patterns B, C, and D with the first one. The pattern of salt effect on the product distribution (% of ROPh, o- and p-RC6H4OH, and p-MeC6H4CH=CH2) for 1 is also compatible with the kp–kt pattern B.
对于纯苯酚中光学活性 1-(对甲基苯基)乙基对硝基苯甲酸酯(ROPNB;(1))的苯解作用,苯氧化钠对极性速率常数(kp)和滴定速率常数(kt)的盐效应呈现出模式 B。其他模式 A、C 和 D 以前分别在对-MeO- (2)、对-H- (3) 和对-NO2-取代基 (4) 的 1-苯乙基对硝基苯甲酸酯的苯解中观察到过。因此,随着中间体稳定性的降低,kp-kt 模式的变化顺序为 A→B→C→D,依次为 2>1>3>4。所有 kp-kt 模式都可以与产物形成的离子对阶段相关联,即模式 A 与第二个离子对中间体相关联,模式 B、C 和 D 与第一个离子对中间体相关联。盐对 1 的产物分布(ROPh、邻和对-RC6H4OH 以及对-MeC6H4CH=CH2 的百分比)的影响模式也与 kp-kt 模式 B 相符。