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相关概念视频

Chirality02:25

Chirality

33.3K
Chirality is a term that describes the lack of mirror symmetry in an object. In other words, chiral objects cannot be superposed on their mirror images. For example, our feet are chiral, as the mirror image of the left foot, the right foot, cannot be superposed on the left foot.
Chiral objects exhibit a sense of handedness when they interact with another chiral object. For example, our left foot can only fit in the left shoe and not in the right shoe. Achiral objects — objects that have...
33.3K
Molecules with Multiple Chiral Centers02:25

Molecules with Multiple Chiral Centers

16.7K
Molecules that possess multiple chiral centers can afford a large number of stereoisomers. For instance, while some molecules like 2-butanol have one chiral center, defined as a tetrahedral carbon atom with four different substituents attached, several molecules like butane-2,3-diol have multiple chiral centers. A simple formula to predict the number of stereoisomers possible for a molecule with n chiral centers is 2n. However, there can be a lower number where some of the stereoisomers are...
16.7K
Chirality in Nature02:30

Chirality in Nature

18.6K
Chirality is the most intriguing yet essential facet of nature, governing life’s biochemical processes and precision. It can be observed from a snail shell pattern in a macroscopic world to an amino acid, the minutest building block of life. Most of the snails around the world have right-coiled shells because of the intrinsic chirality in their genes. All the amino acids present in the human body exist in an enantiomerically pure state, except for glycine - the sole achiral amino acid.
18.6K
Chirality at Nitrogen, Phosphorus, and Sulfur02:30

Chirality at Nitrogen, Phosphorus, and Sulfur

7.5K
Chirality is most prevalent in carbon-based tetrahedral compounds, but this important facet of molecular symmetry extends to sp3-hybridized nitrogen, phosphorus and sulfur centers, including trivalent molecules with lone pairs. Here, the lone pair behaves as a functional group in addition to the other three substituents to form an analogous tetrahedral center that can be chiral.
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
7.5K
Prochirality02:05

Prochirality

5.4K
The concept of prochirality leads to the nomenclature of the individual faces of a molecule and plays a crucial role in the enantioselective reaction. It is a concept where two or more achiral molecules react to produce chiral products. A typical process is the reaction of an achiral ketone to generate a chiral alcohol. Here, the achiral reactant reacts with an achiral reducing agent, sodium borohydride, to generate an equimolar mixture of the chiral enantiomers of the product. For example, an...
5.4K
Fischer Projections02:18

Fischer Projections

18.1K
Learning to draw Fischer projections of molecules and understanding their relevance plays a crucial role in the visual depiction of organic molecules. A Fischer projection is a two-dimensional projection on a planar surface to simplify the three-dimensional wedge–dash representation of molecules. This is especially helpful in the case of molecules with multiple chiral centers that can be difficult to draw. Here, all the bonds of interest are represented as horizontal or vertical lines.
18.1K

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相关实验视频

Updated: Apr 18, 2026

Fabricating van der Waals Heterostructures with Precise Rotational Alignment
09:25

Fabricating van der Waals Heterostructures with Precise Rotational Alignment

Published on: July 5, 2019

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永恒自行推进的奇拉单晶.

Manas K Panda1, Tomče Runčevski, Ahmad Husain

  • 1New York University Abu Dhabi , P.O. Box 129188, Abu Dhabi, United Arab Emirates.

Journal of the American Chemical Society
|January 13, 2015
PubMed
概括

化酸晶体在加热时表现出强大的,可重复的自我激活,这是由于独特的结构相位过渡. 这种热效应,与其他效应不同,避免了晶体的分解,为材料执行提供了一种新的机制.

科学领域:

  • 材料科学 材料科学 材料科学
  • 晶体学 晶体学是指结晶学.
  • 物理化学 物理化学

背景情况:

  • 热材料在加热时会经历快速的形状变化.
  • 现有的热材料在启动过程中经常分解.
  • 基拉酸 (PGA) 是一种具有独特固态特性潜力的分子.

研究的目的:

  • 为了研究在纯 D-和 L-pyroglutamic 酸 (PGA) 晶体中的自我激活机制.
  • 描述与PGA中热效应相关的结构和热性能.
  • 为了比较奇拉PGA与其他热材料的驱动行为.

主要方法:

  • 单晶合成和表征. 单晶合成和表征.
  • 差分扫描热量计 (DSC) 用于相位过渡分析.
  • 用X射线衍射 (XRD) 来确定晶体结构和热膨胀系数.
  • 在现场的光学显微镜观察自动启动.

主要成果:

  • 度纯净的D-和L-PGA晶体在加热时呈现反复的自我激活,而racemate是不活跃的.
  • 执行是强大的和可重复的,没有晶体恶化,归因于一个低维的结网.
  • 该β多态表现出显著的负双轴和正单轴热膨胀,这是热效应的关键因素.

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Crystallization and Structural Determination of an Enzyme:Substrate Complex by Serial Crystallography in a Versatile Microfluidic Chip
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Fabricating van der Waals Heterostructures with Precise Rotational Alignment
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An Electrochemical Cholesteric Liquid Crystalline Device for Quick and Low-Voltage Color Modulation
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Crystallization and Structural Determination of an Enzyme:Substrate Complex by Serial Crystallography in a Versatile Microfluidic Chip
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结论:

  • 状PGA晶体表现出一种由弹性变形和异常热膨胀驱动的新,强大的热效应.
  • 这些发现表明,热效应可以发生在具有异性热膨胀和有限结合的软晶体中.
  • 这项工作为设计具有更强耐用性的新自动执行材料开辟了道路.