充电器在哪里? 气态离子中的质子位随着水合而变化
Terrence M Chang1, James S Prell, Erika R Warrick
1Department of Chemistry, University of California, Berkeley, California 94720-1460, United States.
Journal of the American Chemical Society
|September 8, 2012
概括
水分子会影响气态离子中的质子位,如p-aminobenzoic acid (PABA) 和它的甲基 (PABAOMe). 特定的水合水平将质子从碳氧转移到氨基,模仿溶液的行为.
科学领域:
- 物理化学 物理化学
- 化学物理 化学物理
- 频谱学是一种光谱学.
背景情况:
- 气态离子中的质子位可能与溶液中的质子位不同.
- 了解溶解效应对于解释质谱数据至关重要.
研究的目的:
- 研究水在稳定气相中的p-aminobenzoic acid (PABA) 和p-aminobenzoic acid甲基 (PABAOMe) 的质子位点中的作用.
- 为了确定诱导从碳酸氧到氨基的质子化部位的切换所需的水分子数量.
主要方法:
- 电子喷射电离 (ESI) 与红外光解离 (IRPD) 光谱相结合.
- 计算化学,包括使用各种函数的DFT计算 (B3LYP,MP2, ωB97X-D) 和基础集 (6-311++G**).
主要成果:
- 在PABA和PABAOMe的碳酸氧中,以最小的水 (0-1分子) 发生质子化.
- 对于3个水分子的PABAOMeH (((+) 和具有≥6个水分子的PABAH (((+) 的氨基,质子转换为氨基.
- ωB97X-D/6-311++G**计算方法与实验结果达成最佳一致.
结论:
- 结合和共振移位显著影响质子化部位的稳定性.
- 稳定溶液相质突位所需的水分子数量对于PABAOMeH (((+) 低于PABAH (((+)).
- 结果提供了有关电气喷雾电离脱溶过程中电荷位点稳定和结构转换的见解.
相关概念视频
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In ordinary chemical reactions, the nucleus — which contains the protons and neutrons of each atom and thus identifies the element — remains unchanged. Electrons, however, can be added to atoms by transfer from other atoms, lost by transfer to other atoms, or shared with other atoms. The transfer and sharing of electrons among atoms govern the chemistry of the elements. During the formation of some compounds, atoms gain or lose electrons to form electrically charged particles called ions.
02:54Ions as Acids and Bases
Salts with Acidic Ions
Salts are ionic compounds composed of cations and anions, either of which may be capable of undergoing an acid or base ionization reaction with water. Aqueous salt solutions, therefore, may be acidic, basic, or neutral, depending on the relative acid-base strengths of the salt’s constituent ions. For example, dissolving the ammonium chloride in water results in its dissociation, as described by the equation:
Salts are ionic compounds composed of cations and anions, either of which may be capable of undergoing an acid or base ionization reaction with water. Aqueous salt solutions, therefore, may be acidic, basic, or neutral, depending on the relative acid-base strengths of the salt’s constituent ions. For example, dissolving the ammonium chloride in water results in its dissociation, as described by the equation:
02:42Aqueous Solutions and Heats of Hydration
Water and other polar molecules are attracted to ions. The electrostatic attraction between an ion and a molecule with a dipole is called an ion-dipole attraction. These attractions play an important role in the dissolution of ionic compounds in water.
When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution because water molecules surround and solvate the ions, reducing the strong electrostatic forces between them. This process...
When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution because water molecules surround and solvate the ions, reducing the strong electrostatic forces between them. This process...
03:38Polyprotic Acids
Acids are classified by the number of protons per molecule that they can give up in a reaction. Acids such as HCl, HNO3, and HCN that contain one ionizable hydrogen atom in each molecule are called monoprotic acids. Their reactions with water are:
02:42Formal Charges
In some cases, there are seemingly more than one valid Lewis structures for molecules and polyatomic ions. The concept of formal charges can be used to help predict the most appropriate Lewis structure when more than one reasonable structure exists.
02:54Lewis Structures of Molecular Compounds and Polyatomic Ions
To draw Lewis structures for complicated molecules and molecular ions, it is helpful to follow a step-by-step procedure as outlined: