Tianjin Key Laboratory of Chemical Process Safety and Equipment Technology, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300350, P. R. China.
School of Safety Supervision, North China Institute of Science and Technology, No. 467 Academy Street, Sanhe Yanjiao Development Zone, Langfang 065201, P. R. China.
Phys Chem Chem Phys. 2022 May 4;24(17):10394-10407. doi: 10.1039/d1cp05983a.
Although synthesis of oligoaniline (OANI) by persulfate and aniline has been investigated in the recent years, the impact of phenol on the synthesized soluble OANI is still not clear. In this study, our results indicate that phenol and pH mediate the production of the blue water-soluble OANI (OANI) in the reaction between sodium persulfate (SPS) and aniline under alkaline conditions, and the yields of OANI increase with increasing concentrations of phenol and pH values. Quenching experiments rule out the contributions of SO˙ and ˙OH to aniline oxidation and imply that the non-radical activation of SPS is an important pathway in the formation of OANI. MALDI-TOF-MS analysis indicates that phenol apparently inhibits the polymerization degree of aniline in that the molecular weights of OANI gradually decrease from 1586.4 to 684.6 when phenol is increased from 0 to 2.0 mM. FTIR and Raman analyses confirm the structure of aniline oligomers in OANI and indicate that phenol inhibits the phenazine-like structure in OANI and facilitates the transformation of benzenoid rings to quinoid rings in the oxidation products. However, simultaneous activation of SPS by phenol and aniline is likely to occur in the reaction system with the formation of PhNH˙, as indicated by DFT calculations. The high scavenging reactivity of phenol towards both PhNH˙ and PhNH˙ implies that PhNH˙ and PhNH˙ are not the intermediates in the formation of OANI. DFT calculations also reveal that apart from the one-electron transfer pathway between aniline and SPS, the two-electron transfer pathway is also likely to occur in the presence of phenol, resulting in the formation of PhNH/PhN˙˙ without producing PhNH˙ and PhNH˙. The produced PhNH/PhN˙˙ intermediates then couple with aniline, PhNH, aminophenyl sulfate and its hydrolysate to form dimers, trimers, oligomers, and eventually OANI. This study not only describes a novel method to prepare water-soluble OANI, but also gives new insight on the importance of phenol in the production of OANI.
虽然近年来已经研究了过硫酸盐和苯胺合成寡聚苯胺（OANI），但苯酚对合成可溶性 OANI 的影响尚不清楚。在本研究中，我们的结果表明，在碱性条件下过硫酸钠（SPS）和苯胺之间的反应中，苯酚和 pH 值调节蓝色水溶性 OANI（OANI）的产生，并且随着苯酚和 pH 值的增加，OANI 的产率增加。猝灭实验排除了 SO˙和˙OH 对苯胺氧化的贡献，并暗示 SPS 的非自由基活化是形成 OANI 的重要途径。MALDI-TOF-MS 分析表明，苯酚明显抑制苯胺的聚合度，当苯酚从 0 增加到 2.0mM 时，OANI 的分子量逐渐从 1586.4 降低到 684.6。FTIR 和 Raman 分析证实了 OANI 中苯胺低聚物的结构，并表明苯酚抑制了 OANI 中的吩嗪样结构，并促进了氧化产物中苯环向醌环的转化。然而，如 DFT 计算所示，在反应体系中，苯酚同时激活 SPS 和苯胺很可能发生，形成 PhNH˙。高的苯酚对 PhNH˙和 PhNH˙的清除反应性表明 PhNH˙和 PhNH˙不是 OANI 形成的中间体。DFT 计算还表明，除了苯胺和 SPS 之间的单电子转移途径外，在苯酚存在下，还可能发生双电子转移途径，导致 PhNH/PhN˙˙的形成，而不会产生 PhNH˙和 PhNH˙。生成的 PhNH/PhN˙˙中间体然后与苯胺、PhNH、氨基苯硫酸盐及其水解产物偶联，形成二聚体、三聚体、低聚物，最终形成 OANI。本研究不仅描述了一种制备水溶性 OANI 的新方法，而且还深入了解了苯酚在 OANI 生产中的重要性。
