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Radical Reactivity: Electrophilic Radicals

Radical Reactivity: Electrophilic Radicals

Radicals adjacent to electron‐withdrawing groups are called electrophilic radicals. These radicals readily react with nucleophilic alkenes. For example, the malonate radical, in which the radical center is flanked by two electron‐withdrawing groups, reacts readily with butyl vinyl ether, which consists of an electron‐donating oxygen substituent. The reaction between electrophilic malonate radical and nucleophilic vinyl ether is favored because the radical has a...

Radical Reactivity: Nucleophilic Radicals

Radical Reactivity: Nucleophilic Radicals

Radicals adjacent to electron-donating groups are called nucleophilic radicals. These radicals readily react with electrophilic alkenes. The SOMO–LUMO interactions are the driving force for the reaction, where the high-energy SOMO of the electron-rich, nucleophilic radicals interacts with the low-energy LUMO of the electron-deficient, electrophilic alkenes. Such SOMO–LUMO interactions are the basis of reactive radical traps, affecting the selectivity in radical reactions. For...

Radical Anti-Markovnikov Addition to Alkenes: Mechanism

Radical Anti-Markovnikov Addition to Alkenes: Mechanism

The reaction of hydrogen bromide with alkenes in the presence of hydroperoxides or peroxides proceeds via anti-Markovnikov addition. The radical chain reaction comprises initiation, propagation, and termination steps.
The mechanism starts with chain initiation, which involves two steps. In the first chain initiation step, a weak peroxide bond is homolytically cleaved upon mild heating to form two alkoxy radicals. In the second initiation step, a hydrogen atom is abstracted by the alkoxy...

Radical Anti-Markovnikov Addition to Alkenes: Overview

Radical Anti-Markovnikov Addition to Alkenes: Overview

The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl bromides.

Alkali Metals

Alkali Metals

Group 1 elements are soft and shiny metallic solids. They are malleable, ductile, and good conductors of heat and electricity. The melting points of the alkali metals are unusually low for metals and decrease going down the group, while the density increases going down the group with the exception of potassium (Table 1).
Table 1: Properties of the alkali metals

Regioselectivity of Electrophilic Additions-Peroxide Effect

Regioselectivity of Electrophilic Additions-Peroxide Effect

In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.

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Updated: Feb 22, 2026

A Protocol for Safe Lithiation Reactions Using Organolithium Reagents

A Protocol for Safe Lithiation Reactions Using Organolithium Reagents

Published on: November 12, 2016

How Alkali Metal Alkoxides Initiate Organic Radical Reactions.

Seb Tyerman¹, Kenneth F Clark¹, Alexander J Stewart¹

¹Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, U.K.

Journal of the American Chemical Society

|February 20, 2026

Summary

This summary is machine-generated.

Alkali metal alkoxides initiate radical chemistry via benzyne intermediates, not electron transfer. This study reveals simultaneous formation of multiple benzyne types and a novel methylation mechanism.

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Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts

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Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts

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Published on: February 24, 2015

Area of Science:

Organic Chemistry
Reaction Mechanisms

Background:

Alkali metal alkoxides are known to facilitate hydrodehalogenation and coupling reactions of aryl halides.
These reactions were previously thought to involve aryl radical intermediates formed via electron transfer from alkoxides.

Purpose of the Study:

To investigate the mechanism by which alkali metal alkoxides react with aryl halides.
To determine whether electron transfer or deprotonation initiates the radical chemistry.

Main Methods:

Deuterium isotope studies were employed to probe the reaction mechanism.
Reactions were conducted with various alkali metal alkoxides, including potassium tert-butoxide.

Main Results:

The study refutes the electron transfer mechanism, showing deprotonation leads to benzyne intermediates that initiate radical chemistry.
Simultaneous formation of ortho-, meta-, para-, and remote benzynes was observed.
A novel mechanism for methylation of arenes via methyl radicals derived from tert-butoxide was identified.

Conclusions:

The established mechanism involving electron transfer to form aryl radicals is incorrect.
Benzyne intermediates are key to the radical chemistry initiated by alkali metal alkoxides.
The findings reveal new insights into benzyne formation and alkoxide-derived radical chemistry.