• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Chemistry: A European journal >Unimolecular reaction mechanism of an imidazolin-2-ylidene: An iPEPICO study on the complex dissociation of an arduengo-type carbene
【24h】

Unimolecular reaction mechanism of an imidazolin-2-ylidene: An iPEPICO study on the complex dissociation of an arduengo-type carbene

机译：咪唑啉-2-亚烷基的单分子反应机理：ardenengo型卡宾的复合离解的iPEPICO研究

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The photoionization and dissociative photoionization of Im(iPr) _2, 1,3-diisopropylimidazolin-2-ylidene, was investigated by imaging photoelectron photoion coincidence (iPEPICO) with vacuum ultraviolet (VUV) synchrotron radiation. A lone-pair electron of the carbene carbon atom is removed upon ionization and the molecular geometry changes significantly. Only 0.5eV above the adiabatic ionization energy, IE_(ad)=7.52±0.1eV, the carbene cation fragments, yielding propene or a methyl radical in parallel dissociation reactions with appearance energies of 8.22 and 8.17eV, respectively. Both reaction channels appear at almost the same photon energy, suggesting a shared transition state. This is confirmed by calculations, which reveal the rate-determining step as hydrogen-atom migration from the isopropyl group to the carbene carbon center forming a resonance-stabilized imidazolium ion. Above 10.5eV, analogous sequential dissociation channels open up. The first propene-loss fragment ion dissociates further and another methyl or propene is abstracted. Again, a resonance-stabilized imidazolium ion acts as intermediate. The aromaticity of the system is enhanced even in vertical ionization. Indeed, the coincidence technique confirms that a real imidazolium ion is produced by hydrogen transfer over a small barrier. The simple analysis of the breakdown diagram yields all the clues to disentangle the complex dissociative photoionization mechanism of this intermediate-sized molecule. Photoelectron photoion coincidence is a promising tool to unveil the fragmentation mechanism of larger molecules in mass spectrometry.
机译：通过用真空紫外（VUV）同步加速器辐射对光电子光子重合（iPEPICO）进行成像，研究了Im（iPr）_2，1,3-二异丙基咪唑啉-2-亚基的光电离和离解光电离。卡宾碳原子的孤对电子在电离时被去除，分子的几何形状发生显着变化。仅高于绝热电离能IE_（ad）= 7.52±0.1eV 0.5eV，卡宾阳离子片段在平行解离反应中产生丙烯或甲基，其表观能量分别为8.22和8.17eV。两个反应通道都以几乎相同的光子能量出现，表明共有一个过渡态。通过计算证实了这一点，该计算揭示了确定速率的步骤，即氢原子从异丙基迁移至卡宾碳中心形成共振稳定的咪唑鎓离子。高于10.5eV，将打开类似的顺序解离通道。第一个丙烯损失片段离子进一步解离，并提取出另一个甲基或丙烯。同样，共振稳定的咪唑鎓离子充当中间体。即使在垂直电离条件下，系统的芳香性也得以增强。确实，巧合技术证实了真正的咪唑鎓离子是通过氢在小壁垒上的转移而产生的。对分解图的简单分析提供了所有线索，可以弄清该中等大小分子的复杂解离光电离机理。光电子光子重合是揭示质谱中较大分子的断裂机理的有前途的工具。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号