Chapter 20
Radical Chemistry
Radicaux : structure électronique et géométrie
This lesson delves into the geometry of a radical, which is influenced by the electronic structure of the molecule. The principle is similar to that of a ...
Spectroscopie par résonance paramagnétique électronique (RPE) : radicaux organiques
Ideally, an unpaired electron shows a single peak in the EPR spectrum due to the transition between the two spin energy states. However, coupling ...
Formation radicale : Vue d’ensemble
A bond can be broken either by heterolytic bond cleavage to form ions or homolytic bond cleavage to yield radicals. A fishhook arrow is used to ...
Formation radicalaire : Homolyse
A bond is formed between two atoms by sharing two electrons. When this bond is broken by supplying sufficient energy, either two electrons can be taken up ...
Formation radicale : abstraction
The electron of an atom can be abstracted from a compound by a relatively unstable radical to generate a new radical of relatively greater stability. For ...
Formation radicale : Addition
Radicals can be formed by adding a radical to a spin-paired molecule. This is typically observed with unsaturated species, where the addition of a radical ...
Formation radicale : élimination
Another method of radical formation is the elimination process. It is the opposite of the addition route and is driven by the instability of the radical. ...
Réactivité radicale : Vue d’ensemble
Radicals, the highly reactive species, gain stability by undergoing three different reactions. The first reaction involves a radical-radical coupling, in ...
Réactivité radicalaire : effets stériques
The presence of electron-donating, electron-withdrawing, or conjugating groups adjacent to a radical center, imparts electronic stabilization to the ...
Réactivité radicalaire : effets de concentration
In a radical reaction, the concentration of starting materials governs the selectivity of a radical. For example, the reaction between an alkyl halide and ...
Réactivité radicale : radicaux électrophiles
Radicals adjacent to electron‐withdrawing groups are called electrophilic radicals. These radicals readily react with nucleophilic alkenes. For ...
Réactivité radicalaire : radicaux nucléophiles
Radicals adjacent to electron-donating groups are called nucleophilic radicals. These radicals readily react with electrophilic alkenes. The ...
Réactivité radicalaire : intramoléculaire vs intermoléculaire
Radical reactions can occur either intermolecularly or intramolecularly. In an intermolecular radical reaction, a nucleophilic radical adds to an ...
Auto-oxydation radicale
The oxidation of an organic compound in the presence of air or oxygen is called autoxidation. For example, cumene reacts with oxygen to form ...
Oxydation radicalaire des alcools allyliques et benzyliques
Activated manganese(IV) oxide can selectively oxidize allylic and benzylic alcohols via a radical intermediate mechanism. Primary allylic alcohols are ...
Substitution radicalaire : halogénation d’alcanes et de substituants alkyles
In the presence of heat or light, alkanes react with molecular halogens to form alkyl halides by a substitution reaction called radical halogenation. This ...
Halogénation radicalaire : thermodynamique
The thermodynamic favorability of a reaction is determined by the change in Gibbs free energy (ΔG). ΔG has two components- enthalpy (ΔH) ...
Halogénation radicalaire : stéréochimie
Stereochemistry is the study of the different spatial arrangements of atoms in a given molecule. The stereochemistry of radical halogenations can be ...
Substitution radicalaire : chloration allylique
Typically, when alkenes react with halogens at low temperatures, an addition reaction occurs. However, upon increasing the temperature or under reaction ...
Substitution radicale : bromation allylique
In organic synthesis, the formation of products can be altered by changing the reaction conditions. For example, a dibromo addition product is ...
Substitution radicalaire : hydrogénolyse d’halogénures d’alkyle avec de l’hydrure de tributylétain
Radical substitution reactions can be used to remove functional groups from molecules. The hydrogenolysis of alkyl halides is one such reaction, where the ...
Addition radicale anti-Markovnikov aux alcènes : aperçu
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl ...
Addition radicale anti-Markovnikov aux alcènes : mécanisme
The reaction of hydrogen bromide with alkenes in the presence of hydroperoxides or peroxides proceeds via anti-Markovnikov addition. The radical chain ...
Addition radicale anti-Markovnikov aux alcènes : thermodynamique
The anti-Markovnikov addition of hydrogen halides to an alkene is thermodynamically feasible only with HBr. The radical addition reaction with other ...
Diols vicinaux via couplage réducteur d’aldéhydes ou de cétones : aperçu du couplage Pinacol
Wilhelm Rudolph Fittig discovered the pinacol coupling reaction in 1859. It is a radical dimerization reaction and involves the reductive coupling of ...
Alcènes par couplage réducteur d’aldéhydes ou de cétones : réaction de McMurry
The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used ...
α-hydroxycétones par couplage réducteur d’esters : condensation de l’acyloin Vue d’ensemble
The pinacol and McMurry reactions involve the reductive coupling of ketones or aldehydes. Similarly, the bimolecular reductive coupling of two ester ...
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