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Kapitel 20

Radikalchemie

Radikale: Elektronenstruktur und geometrie
Radikale: Elektronenstruktur und geometrie
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 ...
Paramagnetische Elektronenresonanz (EPR) Spektroskopie: Organische Radikale
Paramagnetische Elektronenresonanz (EPR) Spektroskopie: Organische Radikale
Ideally, an unpaired electron shows a single peak in the EPR spectrum due to the transition between the two spin energy states. However, coupling ...
Bildung von Radikalen: Überblick
Bildung von Radikalen: Überblick
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 ...
Bildung von Radikalen: Homolyse
Bildung von Radikalen: 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 ...
Bildung von Radikalen: Abstraktion
Bildung von Radikalen: Abstraktion
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 ...
Bildung von Radikalen: Addition
Bildung von Radikalen: 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 ...
Bildung von Radikalen: Eliminierung
Bildung von Radikalen: Eliminierung
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. ...
Radikal-Reaktivität: Überblick
Radikal-Reaktivität: Überblick
Radicals, the highly reactive species, gain stability by undergoing three different reactions. The first reaction involves a radical-radical coupling, in ...
Radikal-Reaktivität: Sterische Effekte
Radikal-Reaktivität: Sterische Effekte
The presence of electron-donating, electron-withdrawing, or conjugating groups adjacent to a radical center, imparts electronic stabilization to the ...
Radikal-Reaktivität: Konzentrationseffekte
Radikal-Reaktivität: Konzentrationseffekte
In a radical reaction, the concentration of starting materials governs the selectivity of a radical. For example, the reaction between an alkyl halide and ...
Radikal-Reaktivität: Elektrophile Radikale
Radikal-Reaktivität: Elektrophile Radikale
Radicals adjacent to electron‐withdrawing groups are called electrophilic radicals. These radicals readily react with nucleophilic alkenes. For ...
Radikal-Reaktivität: Nukleophile Radikale
Radikal-Reaktivität: Nukleophile Radikale
Radicals adjacent to electron-donating groups are called nucleophilic radicals. These radicals readily react with electrophilic alkenes. The ...
Radikal-Reaktivität: Intramolekular vs Intermolekular
Radikal-Reaktivität: Intramolekular vs Intermolekular
Radical reactions can occur either intermolecularly or intramolecularly. In an intermolecular radical reaction, a nucleophilic radical adds to an ...
Radikalische Autoxidation
Radikalische Autoxidation
The oxidation of an organic compound in the presence of air or oxygen is called autoxidation. For example, cumene reacts with oxygen to form ...
Radikalische Oxidation von Allyl und Benzylalkoholen
Radikalische Oxidation von Allyl und Benzylalkoholen
Activated manganese(IV) oxide can selectively oxidize allylic and benzylic alcohols via a radical intermediate mechanism. Primary allylic alcohols are ...
Radikalische Substitution: Halogenierung von Alkanen
Radikalische Substitution: Halogenierung von Alkanen
In the presence of heat or light, alkanes react with molecular halogens to form alkyl halides by a substitution reaction called radical halogenation. This ...
Radikalische Halogenierung: Thermodynamik
Radikalische Halogenierung: Thermodynamik
The thermodynamic favorability of a reaction is determined by the change in Gibbs free energy (ΔG). ΔG has two components- enthalpy (ΔH) ...
Radikalische Halogenierung: Stereochemie
Radikalische Halogenierung: Stereochemie
Stereochemistry is the study of the different spatial arrangements of atoms in a given molecule. The stereochemistry of radical halogenations can be ...
Radikalische Substitution: Allylische Chlorierung
Radikalische Substitution: Allylische Chlorierung
Typically, when alkenes react with halogens at low temperatures, an addition reaction occurs. However, upon increasing the temperature or under reaction ...
Radikalische Substitution: Allylische Bromierung
Radikalische Substitution: Allylische Bromierung
In organic synthesis, the formation of products can be altered by changing the reaction conditions. For example, a dibromo addition product is ...
Radikalische Substitution: Hydrogenolyse von Alkylhalogeniden mit Tributylzinnhydrid
Radikalische Substitution: Hydrogenolyse von Alkylhalogeniden mit Tributylzinnhydrid
Radical substitution reactions can be used to remove functional groups from molecules. The hydrogenolysis of alkyl halides is one such reaction, where the ...
Radikalische Anti-Markovnikov-Addition an Alkene: Überblick
Radikalische Anti-Markovnikov-Addition an Alkene: Überblick
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl ...
Radikalische Anti-Markovnikov-Addition an Alkene: Mechanismus
Radikalische Anti-Markovnikov-Addition an Alkene: Mechanismus
The reaction of hydrogen bromide with alkenes in the presence of hydroperoxides or peroxides proceeds via anti-Markovnikov addition. The radical chain ...
Radikalische Anti-Markovnikov-Addition an Alkene: Thermodynamik
Radikalische Anti-Markovnikov-Addition an Alkene: Thermodynamik
The anti-Markovnikov addition of hydrogen halides to an alkene is thermodynamically feasible only with HBr. The radical addition reaction with other ...
Vicinale Diole durch reduktive Kupplung von Aldehyden oder Ketonen: Überblick über die Pinakol-Kupplung
Vicinale Diole durch reduktive Kupplung von Aldehyden oder Ketonen: Überblick über die Pinakol-Kupplung
Wilhelm Rudolph Fittig discovered the pinacol coupling reaction in 1859. It is a radical dimerization reaction and involves the reductive coupling of ...
Alkene durch reduktive Kupplung von Aldehyden oder Ketonen: McMurry-Reaktion
Alkene durch reduktive Kupplung von Aldehyden oder Ketonen: McMurry-Reaktion
The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used ...
α-Hydroxyketone durch reduktive Kupplung von Estern: Überblick über die Acyloin-Kondensation
α-Hydroxyketone durch reduktive Kupplung von Estern: Überblick über die Acyloin-Kondensation
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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