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Alkyl Halides

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 Alkenes

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.

Formation of Halohydrin from Alkenes

Formation of Halohydrin from Alkenes

An alkene, such as propene, reacts with bromine in the presence of water to yield a halohydrin. Halohydrins contain a halogen and a hydroxyl group attached to adjacent carbons. When the halogen is bromine, it is called a bromohydrin, while a chlorohydrin has chlorine as the halogen.

Electrophilic Aromatic Substitution: Fluorination and Iodination of Benzene

Electrophilic Aromatic Substitution: Fluorination and Iodination of Benzene

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.

Radical Halogenation: Thermodynamics

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...

Radical Substitution: Allylic Bromination

Radical Substitution: Allylic Bromination

In organic synthesis, the formation of products can be altered by changing the reaction conditions. For example, a dibromo addition product is formed when propene is treated with bromine at room temperature. In contrast, propene undergoes allylic substitution in non-polar solvents at high temperatures to give 3-bromopropene. In order to avoid the addition reaction, the bromine concentration must be kept as low as possible throughout the reaction. This can be achieved using N-bromosuccinimide...

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Related Experiment Video

Updated: Apr 28, 2026

Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films

Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films

Published on: September 8, 2017

AM1* parameters for bromine and iodine.

Hakan Kayi¹, Timothy Clark

¹Computer-Chemie-Centrum and Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nägelsbachstrasse 25, 91052, Erlangen, Germany.

Journal of Molecular Modeling

|December 6, 2008

Summary

The AM1* semiempirical molecular orbital method now includes parameters for bromine and iodine. This computational chemistry advancement improves accuracy for molecular modeling involving these elements.

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Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films

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Published on: September 8, 2017

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Chemoselective Preparation of 1-Iodoalkynes, 1,2-Diiodoalkenes, and 1,1,2-Triiodoalkenes Based on the Oxidative Iodination of Terminal Alkynes

Chemoselective Preparation of 1-Iodoalkynes, 1,2-Diiodoalkenes, and 1,1,2-Triiodoalkenes Based on the Oxidative Iodination of Terminal Alkynes

Published on: September 12, 2018

Area of Science:

Computational Chemistry
Quantum Chemistry
Theoretical Chemistry

Background:

Semiempirical molecular orbital methods offer a balance between accuracy and computational cost.
The Austin Model 1 (AM1) method is a widely used semiempirical technique.
Parameterization for heavier elements, including halogens, is crucial for expanding the applicability of such methods.

Purpose of the Study:

To extend the AM1 semiempirical molecular orbital technique by parameterizing it for bromine (Br) and iodine (I).
To evaluate the performance of the extended method, termed AM1*, for systems containing these halogens.

Main Methods:

Parameterization of the AM1* method for Br and I.
Inclusion of d-orbitals as polarization functions in the basis sets for Br and I.
Comparison of AM1* performance against other MNDO-like methods.

Main Results:

Successful parameterization of AM1* for Br and I.
AM1* demonstrates performance comparable to other MNDO-like methods utilizing d-orbitals.
AM1* outperforms methods relying solely on sp-basis sets for these elements.

Conclusions:

The AM1* method, now parameterized for Br and I, provides a more accurate computational tool for molecular modeling.
The inclusion of d-orbitals is essential for achieving reliable results with AM1* for these elements.
The expanded parameter set for AM1* covers a broader range of chemical species, enhancing its utility in theoretical chemistry research.