季戊四醇双缩醛水解反应过程的~1H NMR在线研究

On-line Tracking Investigation on the Hydrolysis Process of Pentaerythritol Diacetals with 1H NMR

提出了一种采用1H NMR跟踪研究季戊四醇双缩醛水解的新方法,研究了季戊四醇双缩醛水解反应历程以及不同反应条件和不同基团对其水解速率的影响。以季戊四醇双缩醛为原料,在酸性条件下对其进行水解。水解反应在核磁管内进行,采用1H NMR技术对反应进行在线跟踪,并对其进行了定量和定性分析。研究结果表明:季戊四醇双缩醛的水解速率随温度的升高、酸性的增强而加快。苯环上不同取代基影响其水解速率,推电子基有利于水解,吸电子基不利于水解。苯环上的取代基位置影响水解速率,推电子基水解速率由快到慢依次为对位>邻位>间位;吸电子基水解速率由快到慢依次为间位>对位>邻位。此方法速度快、重复性好,实验研究结果为此类季戊四醇双缩醛的水解提供了理论参考依据。

The hydrolysis process of pentaerythritol diacetals, including influence of reaction rate under different reaction conditions and different substituted groups on the aromatic ring of the reaction substrates, was studied with 1H NMR spectra. With pentaerythritol diacetals as the starting materials, their hydrolysis process was detected in the NMR tube under acidic conditions. The experimen- tal results showed that the hydrolysis rate of pentaerythritol diacetals was increased with the rising of reaction temperature or the acidity of the reaction condition. The electron-donated groups on the aro- matic ring of the reaction substrates could accelerate the hydrolysis; However, the electron-with- drawn groups could decelerate the reaction. The reaction rate sequence with the same electron-dona- ted groups on the aromatic ring of the reaction substrates is ： para-position 〉 ortho-position 〉 meta-position, and the reaction rate sequence with the same electron-withdrawn groups on the aromatic ring of the reaction substrates is： meta-position 〉 para-position 〉 ortho-position. Therefore, a new method for on-line tracking of the hydrolysis of pentaerythritol diacetals was established. This method has the advantages of speediness and repeatability. The results could provide a theoretical reference for the hydrolysis of pentaerythritol diacetals.