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相关概念视频

Phase Transitions: Melting and Freezing02:39

Phase Transitions: Melting and Freezing

Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
Measuring Reaction Rates03:09

Measuring Reaction Rates

Polarimetry finds application in chemical kinetics to measure the concentration and reaction kinetics of optically active substances during a chemical reaction. Optically active substances have the capability of rotating the plane of polarization of linearly polarized light passing through them—a feature called optical rotation. Optical activity is attributed to the molecular structure of substances. Normal monochromatic light is unpolarized and possesses oscillations of the electrical field in...
Interaction of EM Radiation with Matter: Spectroscopy01:12

Interaction of EM Radiation with Matter: Spectroscopy

Electromagnetic (EM) radiation can be considered an oscillating electric and magnetic field propagating through a medium that can interact with matter in its path. The electric field in the radiation can interact with electrical charges in the atoms or molecules in the matter. On the other hand, the magnetic field can interact with the magnetic field in the atomic nucleus. The study of the interaction between electromagnetic radiation and matter is termed spectroscopy. Spectroscopy is the study...
Molecular Spectroscopy: Absorption and Emission01:14

Molecular Spectroscopy: Absorption and Emission

Molecules possess discrete energy levels called quantum states. Unlike atoms, which have simpler energy levels, molecules possess additional rotational and vibrational energy levels. Each energy level is separated by an energy gap, with the gaps between adjacent electronic, vibrational, and rotational levels varying significantly. The three types of energy levels in a diatomic molecule are shown in Figure 1.
UV–Vis Spectroscopy: Molecular Electronic Transitions01:16

UV–Vis Spectroscopy: Molecular Electronic Transitions

In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this process,...
Raman Spectroscopy: Overview01:20

Raman Spectroscopy: Overview

The underlying principle of Raman spectroscopy is based on the interaction between light and matter, specifically molecules' inelastic scattering of photons. When a monochromatic beam of light, typically from a laser source, interacts with a sample, most scattered light has the same frequency as the incident light. This is known as Rayleigh scattering.
However, a small fraction of the scattered light exhibits a frequency shift due to the exchange of energy between the incident photons and the...

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Qualitative Identification of Carboxylic Acids, Boronic Acids, and Amines Using Cruciform Fluorophores
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Published on: August 19, 2013

皮罗西卡姆的机色化伴随着通过光谱方法探测的分子间质子转移和固体相变化.

Agam R Sheth1, Joseph W Lubach, Eric J Munson

  • 1Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Weaver-Densford Hall, 308 Harvard Street SE, Minneapolis, MN 55455-0343, USA.

Journal of the American Chemical Society
|May 5, 2005
PubMed
概括

机械应力将晶体皮洛克萨姆转化为黄色的无形皮洛克萨姆,归因于带电分子. 这种机械色谱,通过固态NMR量化,突出显示了机械应力诱导障碍期间的质子转移.

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科学领域:

  • 固态化学 固态化学
  • 材料科学是一种材料科学.
  • 物理化学 物理化学

背景情况:

  • 皮洛西卡姆是一种非类固醇抗炎药物,表现出不同的固态形式.
  • 了解压力下的结构变化对于药物的稳定性和配方至关重要.
  • 之前的研究指出,黄色的皮洛西卡姆形式含有zwitterionic分子.

研究的目的:

  • 为了研究在机械应力下结晶型皮罗西卡姆的结构和固态变化.
  • 阐明机械应力引起的颜色变化背后的机制.
  • 量化存在于无形阶段的分子物种.

主要方法:

  • 低温研磨以诱导机械应力.
  • 粉末X射线衍光测量 (PXRD) 用于结构分析.
  • 固态UV-Vis光谱检测颜色变化.
  • 可变温度固态 (13)C核磁共振 (NMR) 谱学用于分子量化.
  • 固态扩散反射红外里埃变换光谱 (DRIFTS) 用于功能组分析.

主要成果:

  • 机械应力将无色的晶体piroxicam无水酸转化为黄色的无形piroxicam.
  • 无形皮洛西卡姆的黄色颜色与充电的皮洛西卡姆分子有关.
  • 可变温度固态 (13) C NMR 显示无形阶段含有约 8% 充电的皮罗西卡姆分子.
  • 无色Piroxicam显示出一种倾向于重新结晶成为无色的晶体阶段.

结论:

  • 机械应力诱导Piroxicam的机色,涉及质子转移和颜色从无色变为黄色.
  • 固态核磁共振是一种强大的工具,用于在无标准的无形药物阶段量化中性和带电物种.
  • 这项研究表明,机械应力,固态障碍,质子转移和皮罗西卡姆的颜色变化之间存在直接联系.