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为研究膦酸单烷基酯的化学结构及其物理与化学性能,合成一系列具不同电子效应取代基的对位取代苯基膦酸单酯(Ⅰ)及相应的苯甲基膦酸单酯(Ⅱ)。根据冰点下降法研究结果,这些化合物在苯溶液中系以二聚形式存在,但在醋酸溶液中无缔合现象。它们的纸上层析及纸上电泳行为与酯烷基碳原子数目有关,取代基性质对比移值及泳动值均无显著影响。对位取代苯基膦酸单酯的解离常数及红外光谱特征频率均与取代基性质有关,这类参数与取代基σ常数间有符合Hammett方程式的线性自由能关系,不同酯烷基所形成的直线斜率也不同。对位取代苯甲基膦酸单酯的结构与性能间无定量规律可循,这说明苯环取代基性质由于次甲基相隔,传递受到影响。实验数据有助于说明取代基团对磷原子的诱导效应。从近代价键理论及苯基膦酸酯的水解行为来考虑磷氧键具dπ-pπ结构。
In order to study the chemical structure of phosphonic acid monoalkyl ester and its physical and chemical properties, a series of p-substituted phenylphosphonic acid monoesters (Ⅰ) with different electron-effect substituents and corresponding benzylphosphonic acid monoesters (Ⅱ). According to the results of the freezing point descent method, these compounds exist in dimeric form in benzene solution but not in acetic acid solution. Their paper chromatography and on-paper electrophoresis are related to the number of carbon atoms in the alkyl ester group. There is no significant effect on the relative displacement and migration of the substituent. The dissociation constants and the characteristic frequencies of the IR spectra of p-substituted phenylphosphonic acid monoesters are all related to the properties of the substituents. The linear free energy of these parameters and the σ constants of the substituents conform to the Hammett equation. The formation of different alkyls The slope of the line is also different. There is no quantitative law between the structure and properties of para-substituted benzylphosphonic acid monoester, which shows that the nature of benzene ring substituents is affected by the separation of methine groups. Experimental data help to explain the effect of substitution groups on the induction of phosphorus atoms. From the perspective of the modern valence bond theory and the hydrolysis behavior of phenyl phosphonates, we consider the phosphorus-oxygen bond with dπ-pπ structure.