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Related Concept Videos

Introduction to Electrophilic Addition Reactions of Alkenes02:24

Introduction to Electrophilic Addition Reactions of Alkenes

7.7K
The double bond in a simple, unconjugated alkene is a region of high electron density that can act as a weak base or a nucleophile. The filled π orbital (HOMO) of the double bond can interact with the empty LUMO of an electrophile. A bonding interaction occurs when the electrophile attacks between the two carbons; the electrophile then accepts a pair of electrons from the π bond and undergoes addition across the double bond, yielding a single product.
Addition and elimination...
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Electrophilic Addition to Alkynes: Halogenation02:38

Electrophilic Addition to Alkynes: Halogenation

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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.
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Electrophilic 1,2- and 1,4-Addition of HX to 1,3-Butadiene01:17

Electrophilic 1,2- and 1,4-Addition of HX to 1,3-Butadiene

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The electrophilic addition of hydrogen halides such as HBr to alkenes and nonconjugated dienes gives a single product as per Markovnikov’s rule.
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Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene01:14

Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene

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Electrophilic addition of halogens to alkenes proceeds via a cyclic halonium ion to form a 1,2-dihalide or a vicinal dihalide.
2.4K
Electrophiles02:28

Electrophiles

10.4K
This lesson explains the definition, classification, and characteristic features of an electrophile that are key features of nucleophilic substitution reactions. An analysis of their charge and orbital picture helps understand their reactivity for seeking electrons. Electrophiles can be classified into positive and neutral species. Other classes include free radicals and polar functional groups.
While a positive electrophile, like a proton, reacts due to its vacant, low-energy 1s orbital, the...
10.4K
Electrophilic Addition to Alkynes: Hydrohalogenation02:35

Electrophilic Addition to Alkynes: Hydrohalogenation

9.8K
Electrophilic addition of hydrogen halides, HX (X = Cl, Br or I) to alkenes forms alkyl halides as per Markovnikov's rule, where the hydrogen gets added to the less substituted carbon of the double bond. Hydrohalogenation of alkynes takes place in a similar manner, with the first addition of HX forming a vinyl halide and the second giving a geminal dihalide.
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Adding multiple electrons to helicenes: how they respond?

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  • 1Department of Chemistry, University at Albany, State University of New York Albany NY 12222 USA mpetrukhina@albany.edu.

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This study reveals how chemical reduction affects helicene structures, showing topology- and charge-dependent changes. Understanding these electron-accepting properties advances helicene materials chemistry for new applications.

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Area of Science:

  • Organic Chemistry
  • Materials Science
  • Crystallography

Background:

  • Helicenes exhibit unique chiral, optical, and conducting properties, driving applications in catalysis, optoelectronics, and energy storage.
  • Understanding helicene electron-accepting properties is crucial for materials chemistry, but structural changes upon reduction are under-explored.

Purpose of the Study:

  • To investigate the chemical reduction behavior of helicenes with varying structures and properties.
  • To characterize the structural consequences of electron addition using X-ray diffraction.

Main Methods:

  • Chemical reduction of helicenes with alkali metals.
  • X-ray crystallography for structural characterization of reduced products.
  • Spectroscopic methods and computational calculations to analyze electron addition effects.

Main Results:

  • Chemical reduction induces topology- and charge-dependent structural changes in helicenes.
  • Observed consequences range from reversible geometry perturbations to irreversible core transformations.
  • Unique alkali metal coordination patterns and site-specific reactivity were identified.

Conclusions:

  • The study provides crystallographically confirmed examples of helicene reduction.
  • Revealed structure-property correlations stimulate further research into novel helicene derivatives.
  • Advances the application of helicenes as functional materials through understanding their reduction chemistry.