气相内部质子转移 - 质子化的质子转移
Boris Ucur1, Oisin J Shiels1, Stephen J Blanksby2
1Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia.
概括
电喷离子化 (ESI) 异构体比率受到溶剂催化作用的影响. 这项研究表明,单个甲醇分子介导了对氨基酸中的质子转移,影响了质量分析期间的离子稳定性.
科学领域:
- 分析化学 分析化学
- 物理化学 物理化学
- 质谱测量质量谱测量
背景情况:
- 电子喷射电离 (ESI) 对质谱学至关重要,但对影响质子化异构体的理解因素仍然不完整.
- 准氨基酸 (PABA) 作为研究质子化异构体 (原构体) 的模型,因为它含有氨基和碳酸组.
- 在ESI中的同位素比率对各种物理和化学参数敏感,使优化变得复杂.
研究的目的:
- 为了研究PABA的氨基和碳酸部分之间的时间分解的甲醇催化质子转移.
- 阐明异构化机制,并确定溶剂分子在ESI过程中的作用.
- 量化PABA原体的甲醇催化异构的速率常数.
主要方法:
- 离子陷质谱法用于时间解析的动力学研究.
- 使用计算化学 (DSD-PBEP86-D3BJ/aug-cc-pVDZ) 来探索反应机制和过渡状态.
- 实验是在受控的低压条件下进行的 (2.5 mTorr, 300 K).
主要成果:
- 通过单个甲醇分子介导的双分子机制被确定为PABA异构.
- 伪第一阶速率常数证实了氨基原体的枯竭与碳酸原体的增长相关.
- 甲醇催化异构的第二阶速率常数被确定为 (1.9 ± 0.1) × 10-11 cm3分子-1 s-1.
- 计算分析显示了质子转移的潜水过渡状态.
结论:
- 单溶剂分子可以催化分子内质子转移反应.
- 这种机制在ESI的后期阶段很重要,并影响离子质子化部位和稳定性.
- 了解溶剂介导异构化对于预测和控制质谱学ESI结果至关重要.
相关概念视频
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