Ab initio metadynamics calculations of dimethylamine for probing p K b variations in bulk vs. surface environments
Ab initio metadynamics calculations of dimethylamine for probing p K b variations in bulk vs. surface environments
复制标题
二甲胺的从头算动力学计算，用于探测本体环境与表面环境中的 p K b 变化
DOI：
10.1039/d0cp03832f
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发表时间：
2020
影响因子：
3.3
通讯作者：
Wong, Bryan M.
中科院分区：
文献类型：
--
作者：
Biswas, Sohag;Kwon, Hyuna;Barsanti, Kelley C.;Myllys, Nanna;Smith, James N.;Wong, Bryan M.
碱性常数（英语：basicity constant），或pKb，是碱的一种内在物理性质，它给出了在宏观环境中质子亲和力的量度。虽然pKb通常是根据本体水相定义的，但几项研究表明，该值在空气-水界面处可能存在显著差异（这可能对颗粒表面化学和气溶胶生长建模产生重大影响）。为了提供对表面质子亲和力的机理性洞察，我们进行了从头计算，以（1）探索二甲胺的自由能分布和（2）提供不同溶剂环境中pKb值的合理估计。我们发现，与我们的metadaptics计算得到的自由能分布显示出显着的变化，与界面的水性二甲胺pKb值显着低于在散装水性环境。此外，我们的metadhesics计算表明，这些变化是由于减少在空气-水表面的氢键。总之，我们的量子力学metadaptics计算表明，二甲胺的反应性是令人惊讶的复杂，导致pKb的变化，关键取决于不同的原子相互作用发生在微观分子水平。
The basicity constant, or pKb, is an intrinsic physical property of bases that gives a measure of its proton affinity in macroscopic environments. While the pKb is typically defined in reference to the bulk aqueous phase, several studies have suggested that this value can differ significantly at the air–water interface (which can have significant ramifications for particle surface chemistry and aerosol growth modeling). To provide mechanistic insight into surface proton affinity, we carried out ab initio metadynamics calculations to (1) explore the free-energy profile of dimethylamine and (2) provide reasonable estimates of the pKb value in different solvent environments. We find that the free-energy profiles obtained with our metadynamics calculations show a dramatic variation, with interfacial aqueous dimethylamine pKb values being significantly lower than in the bulk aqueous environment. Furthermore, our metadynamics calculations indicate that these variations are due to reduced hydrogen bonding at the air–water surface. Taken together, our quantum mechanical metadynamics calculations show that the reactivity of dimethylamine is surprisingly complex, leading to pKb variations that critically depend on the different atomic interactions occurring at the microscopic molecular level.