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Halogens

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.

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.

Multiple Halogenation of Methyl Ketones: Haloform Reaction

Multiple Halogenation of Methyl Ketones: Haloform Reaction

A method involving the transformation of methyl ketones to carboxylic acids using excess base and halogen is called the haloform reaction. It begins with the deprotonation of α hydrogen to form an enolate ion which reacts with the electrophilic halogen to give an α-halo ketone. The step continues until all the α protons are substituted to form a trihalomethyl ketone. The resulting molecule is unstable, and in the presence of a hydroxide base, it readily undergoes nucleophilic acyl substitution.

Reactions at the Benzylic Position: Halogenation

Reactions at the Benzylic Position: Halogenation

Benzylic halogenation takes place under conditions that favor radical reactions such as heat, light, or a free radical initiator like peroxide.

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...

α-Halogenation of Carboxylic Acid Derivatives: Overview

α-Halogenation of Carboxylic Acid Derivatives: Overview

Unlike aldehydes and ketones, carboxylic acids do not readily participate in α halogenation reactions via enols or enolate intermediates. However, α-halogenated acids are obtained through other methods. One of the approaches is the Hell–Volhard–Zelinsky (HVZ) reaction, wherein the carboxylic acid is treated with halogen in the presence of PBr3. It involves the conversion of acid to acid halide, which exists in equilibrium with its enol form. The enol attacks the electrophilic halogen to produce...

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Related Experiment Video

Updated: May 17, 2026

Hydrogen Charging of Aluminum using Friction in Water

Hydrogen Charging of Aluminum using Friction in Water

Published on: January 28, 2020

Halogen head light-you can make it.

¹ENT Department, Government Medical College, Amritsar.

Indian Journal of Otolaryngology and Head and Neck Surgery : Official Publication of the Association of Otolaryngologists of India

|November 3, 2012

Summary

This summary is machine-generated.

Upgrade your Clark's tike headlight by replacing the standard bulb with a 12-volt, 55-watt halogen tube. This modification requires a 12-volt, 5-amp transformer for optimal performance and brightness.

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Area of Science:

Automotive Engineering
Lighting Technology

Background:

Standard incandescent bulbs in older lighting systems can be inefficient.
Halogen technology offers improved illumination and longevity.

Purpose of the Study:

To describe a method for upgrading a specific type of headlight.
To detail the components required for a halogen headlight conversion.

Main Methods:

Removal of the original bulb and associated components from the Clark's tike headlight.
Installation of a 12-volt, 55-watt halogen tube and its necessary attachments.

Main Results:

The conversion results in a halogen-powered headlight.
The system requires a 12-volt, 5-amp transformer for peak operational output.

Conclusions:

A simple upgrade path exists for the Clark's tike headlight using halogen technology.
Proper power conversion is essential for achieving maximum output from the halogen tube.