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Related Concept Videos

Halogens03:01

Halogens

24.0K
Group 17 elements, known as halogens, are nonmetals. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine a solid. Astatine is a highly unstable radioactive element, so currently, most of its properties are unknown due to its short half-life. Tennessine is a synthetic element also predicted to be in this group. 
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Electrophilic Addition to Alkynes: Hydrohalogenation02:35

Electrophilic Addition to Alkynes: Hydrohalogenation

12.0K
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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ortho–para-Directing Deactivators: Halogens01:24

ortho–para-Directing Deactivators: Halogens

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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...
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Electrophilic Aromatic Substitution: Fluorination and Iodination of Benzene01:13

Electrophilic Aromatic Substitution: Fluorination and Iodination of Benzene

7.8K
Bromination and chlorination of aromatic rings by electrophilic aromatic substitution reactions are easily achieved, but fluorination and iodination are difficult to achieve. Fluorine is so reactive that its reaction with benzene is difficult to control, resulting in poor yields of monofluoroaromatic products. To address this, Selectfluor reagent is used as a fluorine source in which a fluorine atom is bonded to a positively charged nitrogen.
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Radical Halogenation: Thermodynamics01:34

Radical Halogenation: Thermodynamics

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The thermodynamic favorability of a reaction is determined by the change in Gibbs free energy (ΔG). ΔG has two components- enthalpy (ΔH) and entropy (ΔS). The entropy component is negligible for alkane halogenation because the number of reactants and product molecules are equal. In this case, the ΔG is governed only by the enthalpy component. The most crucial factor that determines ΔH is the strength of the bonds. ΔH can be determined by comparing the energy...
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Halogenation of Alkenes02:46

Halogenation of Alkenes

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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.
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Related Experiment Video

Updated: Mar 17, 2026

Monitoring the Reductive and Oxidative Half-Reactions of a Flavin-Dependent Monooxygenase using Stopped-Flow Spectrophotometry
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Monitoring the Reductive and Oxidative Half-Reactions of a Flavin-Dependent Monooxygenase using Stopped-Flow Spectrophotometry

Published on: March 18, 2012

15.7K

Engineering Flavin-Dependent Halogenases.

J T Payne1, M C Andorfer2, J C Lewis2

  • 1University of Chicago, Chicago, IL, United States; Stanford University, Stanford, CA, United States.

Methods in Enzymology
|July 16, 2016
PubMed
Summary
This summary is machine-generated.

Flavin-dependent halogenases (FDHs) have seen significant advancements in understanding their diversity, structure, and function. Enzyme engineering efforts have successfully created FDH variants with enhanced stability, broader substrate scope, and modified regioselectivity for synthetic applications.

Keywords:
BiocatalysisDirected evolutionFlavinHalogenaseProtein engineering

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From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
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Monitoring the Reductive and Oxidative Half-Reactions of a Flavin-Dependent Monooxygenase using Stopped-Flow Spectrophotometry
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Area of Science:

  • Biocatalysis
  • Enzyme Engineering
  • Organic Chemistry

Background:

  • Flavin-dependent halogenases (FDHs) are crucial enzymes involved in halogenation reactions.
  • Two decades of research have expanded knowledge of FDH diversity, structure, and function.
  • Recent progress focuses on engineering FDHs for synthetic applications.

Purpose of the Study:

  • To review recent advancements in flavin-dependent halogenase engineering.
  • To highlight the development of FDH variants with improved properties.
  • To provide practical protocols for FDH engineering.

Main Methods:

  • Review of random and structure-guided mutagenesis techniques.
  • Discussion of screening methods such as HPLC, mass spectrometry, and spectrophotometry.
  • Presentation of generalized protocols applicable to various FDHs and engineering objectives.

Main Results:

  • Successful engineering of FDH variants with enhanced stability.
  • Development of FDHs with expanded substrate scope.
  • Creation of FDHs with altered regioselectivity for targeted synthesis.

Conclusions:

  • Enzyme engineering has yielded successful FDH variants for synthetic chemistry.
  • The reviewed protocols are generalizable for broad FDH engineering applications.
  • Continued engineering efforts promise further advancements in biocatalysis.