Acta Chimica Sinica ›› 2019, Vol. 77 ›› Issue (4): 358-364.DOI: 10.6023/A18120505 Previous Articles     Next Articles

Article

倍硫磷的甲基在分子内和分子间迁移的质谱研究

任响a, 张小平b, 王雨芬a, 曹静瑜a, 程媛媛b, 冯守华a, 陈焕文b   

  1. a 吉林大学 无机合成与制备化学国家重点实验室 长春 130012;
    b 东华理工大学 江西省质谱科学与仪器重点实验室 南昌 330013
  • 投稿日期:2018-12-17 发布日期:2019-02-25
  • 通讯作者: 冯守华, 陈焕文 E-mail:shfeng@jlu.edu.cn;chw8868@gmail.com
  • 基金资助:

    项目受国家自然科学基金(No.21427802),国家自然科学基金(No.21520102007, 21605017),江西省教育厅基金(No.GJJ160574),江西省质谱科学与仪器重点实验室开放基金(JXMS201803)资助.

Intramolecular and Intermolecular Methyl Migration of Fenthion Studied by Electrospray Ionization Mass Spectrometry

Ren Xianga, Zhang Xiaopingb, Wang Yufena, Cao Jingyua, Cheng Yuanyuanb, Feng Shouhuaa, Chen Huanwenb   

  1. a State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130012;
    b Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China Institute of Technology, Nanchang 330013
  • Received:2018-12-17 Published:2019-02-25
  • Contact: 10.6023/A18120505 E-mail:shfeng@jlu.edu.cn;chw8868@gmail.com
  • Supported by:

    Project supported by the National Natural Science Foundation of China (No. 21427802), the National Natural Science Foundation of China (No. 21520102007, 21605017), Project of Jiangxi Provincial Department of Education (No. GJJ160574), and the Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation Open Fund (JXMS201803).

Methyl transfer reactions are of great significance in the field of synthetic chemistry and life sciences. So far, most of the reported methyl migration reactions have occurred between different types of molecules. Therefore, it is of certain value to search for new methyl transfer reactions. In this study, fenthion, a most common insecticide in the environment, was selected as the studied object, and electrospray ionization mass spectrometry (ESI-MS) was used as the analytical tool to conduct highly sensitive analysis of the reaction system, so as to explore the possibility of methyl transfer reaction in fenthion molecules under the condition of trifluoroacetic acid and nanometer titanium dioxide. Other than m/z 279 (protonated fenthion), some new product ions (m/z 293 and m/z 265) could be observed in the fingerprint MS of fenthion reaction solution. Tandem MS experiments showed that the intensity of product ion m/z 231 (elimination of CH3SH) in the dissociation of m/z 279 from fenthion reaction solution were different from that from protonated fenthion standard. This indicated that the methyl in the fenthion could transfer from oxygen atom to unsaturated sulfur atom via 1,3-methyl transfer, forming isomer a2, which led to the high intensity of product ion m/z 231 in the dissociation of m/z 279 from fenthion reaction solution. Under the assistance of acid, the methyl cation continued to transfer from sulfur atom in a2 to the unsaturated sulfur atom in another fenthion molecule, forming a3 (m/z 293) and a4 via intermolecular methyl transfer reaction, which was verified by tandem MS experiments of ions at m/z 293 and m/z 265. In addition, density functional theory (DFT) calculations were carried out to confirm the mechanism of intramolecular and intermolecular methyl transfer reactions of fenthion. In order to observe the phenomenon of methyl transfer more intuitively, the effects of different acids, metal oxides, reaction time and reaction temperature on the signal intensities of ions at m/z 265 and m/z 293 of intermolecular methyl transfer reactions of fenthion were investigated. It could be concluded that under the conditions of trifluoroacetic acid and nanometer titanium dioxide, and 60℃ ultrasound reaction for 6 h, the proportion of intermolecular methyl transfer reactions of fenthion was the highest. In this study, intramolecular and intermolecular methyl transfer reactions were both discovered and investigated in fenthion, which can not only provide a method to study methyl transfer reactions, but also propose a new idea for the study of degradation of fenthion.

Key words: fenthion, intramolecular methyl transfer, intermolecular methyl transfer, electrospray ionization mass spectrometry, trifluoroacetic acid, nanometer titanium dioxide