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相关概念视频

Prochirality02:05

Prochirality

3.8K
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...
3.8K
Chirality02:25

Chirality

24.2K
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...
24.2K
Chirality at Nitrogen, Phosphorus, and Sulfur02:30

Chirality at Nitrogen, Phosphorus, and Sulfur

5.7K
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...
5.7K
Naming Enantiomers02:21

Naming Enantiomers

20.4K
The naming of enantiomers employs the Cahn–Ingold–Prelog rules that involve assigning priorities to different substituent groups at a chiral center. Each enantiomer, being a distinct molecule, is assigned a unique name by the Cahn–Ingold–Prelog (CIP) rules, also called the R–S system. The prefix R- or S- attached to the chiral centers in an enantiomer is dependent on the spatial arrangement of the four substituents on the chiral center. The R–S system...
20.4K
Stereoisomerism of Cyclic Compounds02:33

Stereoisomerism of Cyclic Compounds

8.9K
In this lesson, we delve into the role of ring conformation and its stability, which determines the spatial arrangement and, consequently, the molecular symmetry and stereoisomerism of cyclic compounds. 1,2-Dimethylcyclohexane is used as a case study to evaluate the possible number of stereoisomers. Here, given the multiple (n = 2) chiral centers, there are 2n = 4 possible configurations that lack a plane of symmetry, as the ring skeleton exists in a non-planar chair conformation. In addition,...
8.9K
Molecules with Multiple Chiral Centers02:25

Molecules with Multiple Chiral Centers

11.7K
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...
11.7K

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相关实验视频

Updated: Jul 2, 2025

Coulomb Explosion Imaging as a Tool to Distinguish Between Stereoisomers
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Coulomb Explosion Imaging as a Tool to Distinguish Between Stereoisomers

Published on: August 18, 2017

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对变压器架构的奇拉性识别困难从字符串表示中学习化学结构.

Yasuhiro Yoshikai1, Tadahaya Mizuno2, Shumpei Nemoto1

  • 1Laboratory of Molecular Pharmacokinetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, Japan.

Nature communications
|February 16, 2024
PubMed
概括

自然语言处理 (NLP) 模型从SMILES字符串中学习分子结构. 这项研究表明,变形金刚很快就会学习部分结构,但需要广泛的训练才能完全理解,特别是对于奇拉性.

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Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates
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Probing the Structure and Dynamics of Interfacial Water with Scanning Tunneling Microscopy and Spectroscopy
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Probing the Structure and Dynamics of Interfacial Water with Scanning Tunneling Microscopy and Spectroscopy

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相关实验视频

Last Updated: Jul 2, 2025

Coulomb Explosion Imaging as a Tool to Distinguish Between Stereoisomers
08:51

Coulomb Explosion Imaging as a Tool to Distinguish Between Stereoisomers

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Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates
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Probing the Structure and Dynamics of Interfacial Water with Scanning Tunneling Microscopy and Spectroscopy
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科学领域:

  • 计算化学是一种计算化学.
  • 机器学习在化学中的应用

背景情况:

  • 对分子描述符的表示学习正在迅速发展.
  • 应用于SMILES字符串的自然语言处理 (NLP) 模型是一个关键领域.
  • 这些NLP模型在理解化学结构方面的可解释性仍未得到充分探索.

研究的目的:

  • 研究NLP模型,特别是变压器如何从SMILES中学习化学结构.
  • 了解模型学习进度与化学结构理解之间的关系.
  • 识别NLP模型学习中的挑战,特别是关于立体化学的挑战.

主要方法:

  • 使用了一个变压器模型,一个代表性的NLP架构.
  • 在SMILES字符串上训练模型,这些字符串代表各种分子.
  • 分析了关于部分和整体分子结构的学习进展.
  • 在不同训练阶段评估分子性质预测准确度.
  • 研究了模型学习性和处理反体的能力.

主要成果:

  • 变压器模型快速学习部分分子结构,但需要长时间的训练才能全面理解.
  • 在整个培训过程中,无论学习阶段如何,分子性质预测的准确性始终保持一致.
  • 该模型在学习性方面表现出重大挑战,经常误解酶体,导致性能停滞.

结论:

  • 像变压器这样的NLP模型对分子结构的不同方面表现出不同的学习轨迹.
  • 扩展培训对于NLP模型来说至关重要,以掌握复杂的化学特征,如性.
  • 这些发现有助于更深入地理解NLP在化学信息学中的应用机制.