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相关概念视频

Polymer Classification: Crystallinity01:21

Polymer Classification: Crystallinity

4.1K
Unlike ionic or small covalent molecules, polymers do not form crystalline solids due to the diffusion limitations of their long-chain structures. However, polymers contain microscopic crystalline domains separated by amorphous domains.
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
4.1K
Molecular and Ionic Solids02:54

Molecular and Ionic Solids

20.5K
Crystalline solids are divided into four types: molecular, ionic, metallic, and covalent network based on the type of constituent units and their interparticle interactions.
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
20.5K
Alkyl Halides02:45

Alkyl Halides

20.7K
Structural Properties
Alkyl halides are halogen-substituted alkanes wherein one or more hydrogen atoms of an alkane is replaced by a halogen atom such as fluorine, chlorine, bromine, or iodine. The carbon atom in an alkyl halide is bonded to the halogen atom, which is sp3-hybridized and exhibits a tetrahedral shape.
Unlike alkyl halides, compounds in which a halogen atom is bonded to an sp2 -hybridized carbon atom of a carbon-carbon double bond (C=C) are called vinyl halides. Whereas aryl...
20.7K
ortho–para-Directing Deactivators: Halogens01:24

ortho–para-Directing Deactivators: Halogens

7.0K
Halogens are ortho–para directors. They are more electronegative than carbon. Therefore, as ring substituents, they can withdraw electrons through the inductive effect and deactivate the aromatic ring towards electrophilic substitution. Halogens also have an electron-donating resonance effect on the ring, which influences the orientation of the incoming electrophile. If an electrophile attacks at the ortho or the para position, the halogen donates electrons and stabilizes the intermediate...
7.0K
Halogenation of Alkenes02:46

Halogenation of Alkenes

20.5K
Halogenation is the addition of chlorine or bromine across the double bond in an alkene to yield a vicinal dihalide. The reaction occurs in the presence of inert and non-nucleophilic solvents, such as methylene chloride, chloroform, or carbon tetrachloride.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
20.5K
Electrophilic Addition to Alkynes: Halogenation02:38

Electrophilic Addition to Alkynes: Halogenation

10.3K
Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
10.3K

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相关实验视频

Updated: Mar 3, 2026

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
06:44

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding

Published on: March 24, 2018

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用于高性能非线性光学晶体材料的离子驱动的多态体.

Yuwei Kang1,2, Can Yang1, Yunjie Wang1

  • 1State Key Laboratory of New Textile Materials and Advanced Processing, Wuhan Textile University Wuhan 430200 China wuqi2011@whu.edu.cn.

Chemical science
|March 2, 2026
PubMed
概括
此摘要是机器生成的。

为非线性光学 (NLO) 设计非中心对称 (NCS) 材料是困难的. 这项研究使用素驱动的方法来创建具有增强第二和生成 (SHG) 效率的NCS结构.

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Hyperspectral Imaging as a Tool to Study Optical Anisotropy in Lanthanide-Based Molecular Single Crystals
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An Electrochemical Cholesteric Liquid Crystalline Device for Quick and Low-Voltage Color Modulation
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Last Updated: Mar 3, 2026

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
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From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding

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Hyperspectral Imaging as a Tool to Study Optical Anisotropy in Lanthanide-Based Molecular Single Crystals
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An Electrochemical Cholesteric Liquid Crystalline Device for Quick and Low-Voltage Color Modulation
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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.
  • 光学是什么?光学是什么?光学是什么?

背景情况:

  • 非中心对称 (NCS) 晶体材料对于非线性光学 (NLO) 应用至关重要.
  • 设计NCS材料是具有挑战性的,因为热力学偏好中心对称结构.
  • 开发NCS材料合成的新策略对于推进NLO技术至关重要.

研究的目的:

  • 展示一种以素驱动的合成NCS材料的策略.
  • 研究素替代对晶体结构和NLO特性的影响.
  • 在基于Sn的混合材料中实现增强的第二和生成 (SHG) 效率.

主要方法:

  • 利用化离子和立体化学活性Sn2+中心之间的竞争性协调.
  • 使用精确的素替代通过不同的化物来源 ([N(C2H5) [4]Cl或[N(C2H5) [4]Br).
  • 合成了[N(C2H5) [4]SnBr3 (Cc和Cmc21阶段) 的两种新多态.
  • 描述合成材料的NLO特性,特别是SHG效率.
  • 执行理论计算以了解SHG响应的起源.

主要成果:

  • 成功合成了两个新的NCS多态,Cc和Cmc21阶段的[N(C2H5)4]SnBr3.
  • 在Cmc21阶段,SHG效率显著提高 (5.6 × KH2PO4),超过了Cc阶段 (2 × KH2PO4).
  • 观察到的SHG性能是基于Sn的有机-无机混合NLO材料中报告的最高性能之一.
  • 理论计算确定[SnBr3]-单位是强烈的SHG反应的主要贡献者.

结论:

  • 素驱动对称性控制是设计NCS材料的可行和有效策略.
  • 这种方法使材料的合理设计能够显著增强SHG反应.
  • 这些发现为开发高性能NLO材料提供了宝贵的见解和参考.