The second-order rate constants k (dm3 mol-1 s-1) for the alkaline hydrolysis of meta-, para-, and ortho-substituted phenyl tosylates 4-CH3C6H4SO2OC6H4-X in aqueous 0.5 M Bu4NBr have been measured spectrophotometrically in a wide temperature range. The log k values for ortho-substituted derivatives at various temperatures together with meta- and para-substituted derivatives were analyzed using the modified Fujita-Nishioka equation log km,p,ortho = c0 + c1(m,p,ortho)σ° + c2(ortho)σI + c3(1/T) + c4(m,p,ortho)(1/T)σ° + c5(ortho)(1/T)σI. In order to study the dependence of substituent effects, especially ortho inductive and resonance terms on different solvent parameters, the following equation was used: ∆log km,p,ortho = c0 + c1(m,p,ortho)σ° + c2(ortho)σI + c3∆E + c4∆Y + c5∆P + c6(m,p,ortho)∆Eσ° + + c7(m,p,ortho)∆Yσ° + c8(m,p,ortho)∆Pσ° + c9(ortho)∆EσI + c10(ortho)∆YσI + c11(ortho)∆PσI. ∆log k = log kX - log kH, σ° and σI, are the Taft polar and inductive substituent constants, E, Y and P, are the solvent electrophilicity, polarity and polarizability parameters, respectively. In data treatment ∆E = ES - EH2O, ∆Y = YS - YH2O, ∆P = PS - PH2O were used. The solvent electrophilicity was found to be the main factor responsible for changes in the ortho, para, and meta polar substituent effects with medium. The variation of the ortho inductive term with the solvent electrophilicity ES was found to be twice smaller than that for para substituents, while the ortho resonance term appeared to vary with solvent nearly similarly to that for para substituents. The ortho effect caused by the supplementary inductive effect from ortho position was found to disappear in a solvent whose electrophilic solvating power is comparable to pure DMSO (E ≈ 4).
对于在水性0.5 M Bu4NBr中对4-CH3C6H4SO2OC6H4-X进行的邻位、间位和对位取代苯甲基对磺酸酯碱性水解的二阶速率常数k(dm3 mol-1 s-1)已经在广泛的温度范围内通过光谱法测量。各种温度下邻位取代衍生物的对数k值以及间位和对位取代衍生物已经使用改进的Fujita-Nishioka方程log km,p,ortho = c0 + c1(m,p,ortho)σ° + c2(ortho)σI + c3(1/T) + c4(m,p,ortho)(1/T)σ° + c5(ortho)(1/T)σI 进行分析。为了研究取代基效应的依赖性,尤其是对不同溶剂参数上的对位感应和共振项的依赖性,使用了以下方程:Δlog km,p,ortho = c0 + c1(m,p,ortho)σ° + c2(ortho)σI + c3ΔE + c4ΔY + c5ΔP + c6(m,p,ortho)ΔEσ° + c7(m,p,ortho)ΔYσ° + c8(m,p,ortho)ΔPσ° + c9(ortho)ΔEσI + c10(ortho)ΔYσI + c11(ortho)ΔPσI。Δlog k = log kX - log kH,σ°和σI,是Taft极性和归纳取代基常数,E,Y和P,是溶剂亲电性、极性和极化率参数,分别。在数据处理中ΔE = ES - EH2O,ΔY = YS - YH2O,ΔP = PS - PH2O。发现溶剂亲电性是导致对位、邻位和间位极性取代基效应变化的主要因素。随着溶剂亲电性ES的变化,对位感应项的变化比邻位取代基小了一倍,而对位共振项的变化似乎与邻位取代基几乎相似。由于来自对位位置的补充感应效应引起的对位效应被发现在其亲电性溶剂的溶剂化能力与纯DMSO相当时消失(E≈4)。