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Related Concept Videos

Halogens03:01

Halogens

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.
Alkyl Halides02:45

Alkyl Halides

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...
Halogenation of Alkenes02:46

Halogenation of Alkenes

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.
Mass Spectrometry: Alkyl Halide Fragmentation01:22

Mass Spectrometry: Alkyl Halide Fragmentation

Chlorine isotopes exist as 35Cl and 37Cl in a 3:1 ratio, while bromine isotopes exist as 79Br and 81Br in a 1:1 ratio. The mass spectrum of alkyl halides typically produces two distinct molecular ion peaks, the molecular ion peak, [M], and the molecular ion plus two, [M + 2] peak. The relative heights of these two peaks are proportional to the isotopic abundance ratios of the halide. For example, 2‐chloropropane and 1‐bromopropane display two peaks with relative peak heights in a 3:1 and 1:1...
Radical Substitution: Halogenation of Alkanes and Alkyl Substituents01:27

Radical Substitution: Halogenation of Alkanes and Alkyl Substituents

In the presence of heat or light, alkanes react with molecular halogens to form alkyl halides by a substitution reaction called radical halogenation. This reaction has three steps: initiation, propagation, and termination, as seen in the radical chlorination of methane to produce methyl chloride.
In the initiation step of the reaction, the chlorine molecule undergoes homolytic cleavage in the presence of light or heat, forming two highly reactive chlorine radicals. Propagation occurs in two...
Radical Halogenation: Thermodynamics01:34

Radical Halogenation: Thermodynamics

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 between bonds broken and bonds...

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Related Experiment Video

Updated: Jun 17, 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

Halogens in the troposphere.

Barbara J Finlayson-Pitts1

  • 1Department of Chemistry, University of California Irvine, Irvine, CA 92697-2025, USA. bjfinlay@uci.edu

Analytical Chemistry
|January 1, 2010
PubMed
Summary
This summary is machine-generated.

Inorganic halogen gases are crucial for atmospheric chemistry but often undetected. This study reviews current and needed methods for measuring these vital atmospheric components.

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Last Updated: Jun 17, 2026

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Area of Science:

  • Atmospheric Chemistry
  • Environmental Science
  • Analytical Chemistry

Background:

  • Inorganic halogen gases are hypothesized to significantly influence lower atmospheric chemistry.
  • Despite their presumed importance, many inorganic halogens remain undetected in ambient air.

Purpose of the Study:

  • To review current analytical techniques for detecting and measuring inorganic halogens in the atmosphere.
  • To identify future needs and challenges in the field of atmospheric inorganic halogen analysis.

Main Methods:

  • Review of existing literature on analytical methods for inorganic halogens.
  • Discussion of instrumental techniques and sampling strategies.
  • Identification of knowledge gaps and technological limitations.

Main Results:

  • Current methods for inorganic halogen detection are insufficient for many species.
  • Significant advancements are needed in sensitivity, selectivity, and real-time measurement capabilities.
  • Lack of routine measurements hinders understanding of halogen cycling in the atmosphere.

Conclusions:

  • Accurate measurement of inorganic halogens is essential for understanding atmospheric processes.
  • Further development of analytical methodologies is critical for atmospheric research.
  • Addressing current limitations will enable better characterization of atmospheric halogen chemistry.