Related Experiment Video
Updated: Jun 20, 2026
![[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59739.jpg&w=3840&q=50)
09:12
[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst
Published on: May 21, 2019
Electrophile affinity: a reactivity measure for aromatic substitution
Gergana Koleva1, Boris Galabov, Judy I Wu
1Department of Chemistry, University of Sofia, Sofia 1164, Bulgaria.
Journal of the American Chemical Society
|September 26, 2009
Summary
Electrophile Affinity (Ealpha) quantifies reactivity and regioselectivity in electrophilic aromatic substitution reactions. This new metric shows high correlation with experimental data for chlorination, nitration, and benzylation of benzene derivatives.
Area of Science:
- Organic Chemistry
- Physical Chemistry
Background:
- Electrophilic aromatic substitution (S(E)Ar) reactions are fundamental in organic synthesis.
- Understanding the factors governing reactivity and regioselectivity is crucial for predicting reaction outcomes.
Purpose of the Study:
- To rationalize the reactivity and regioselectivity of electrophilic chlorination, nitration, and alkylation of benzene derivatives.
- To introduce and validate a new theoretical parameter, Electrophile Affinity (Ealpha), for quantifying these processes.
Main Methods:
- Comparison of literature data for partial rate factors (ln f) with theoretical reactivity parameters.
- Theoretical evaluation of Electrophile Affinity (Ealpha) based on the energy change during arenium ion formation.
- Correlation analysis between Ealpha, electrostatic potential at nuclei (EPN) values, and experimental partial rate factors.
Main Results:
- High correlation coefficients (r > 0.97) were observed between Ealpha and partial rate factors for chlorination, nitration, and benzylation.
- Satisfactory correlations were found between EPN values and experimental partial rate factors for chlorination and nitration.
- A discrepancy in correlations for benzylation was noted, attributed to steric effects of the benzyl group.
Conclusions:
- Electrophile Affinity (Ealpha) is a useful quantitative measure for predicting reactivity and regiochemistry in S(E)Ar reactions.
- EPN values effectively reflect electron density variations relevant to chlorination and nitration.
- Steric factors significantly influence reactions involving bulky electrophiles like the benzyl moiety.
More Related Videos
Related Concept Videos
01:16Electrophilic Aromatic Substitution: Overview
In an electrophilic aromatic substitution reaction, an electrophile substitutes for a hydrogen of an aromatic compound.
01:11Nucleophilic Aromatic Substitution: Elimination–Addition
Simple aryl halides do not react with nucleophiles. However, nucleophilic aromatic substitutions can be forced under certain conditions, such as high temperatures or strong bases. The mechanism of substitution under such conditions involves the highly unstable and reactive benzyne intermediate. Benzyne contains equivalent carbon centers at both ends of the triple bond, each of which is equally susceptible to nucleophilic attack. This 50–50 distribution of products is confirmed through isotopic...
01:30Nucleophilic Aromatic Substitution: Addition–Elimination (SNAr)
Nucleophilic substitution in aromatic compounds is feasible in substrates bearing strong electron-withdrawing substituents positioned ortho or para to the leaving group. The reaction proceeds via two steps: the addition of the nucleophile and the elimination of the leaving group.
The reaction begins with an attack of the nucleophile on the carbon that holds the leaving group. This results in the delocalization of the π electrons over the ring carbons. The resonance interaction between the...
The reaction begins with an attack of the nucleophile on the carbon that holds the leaving group. This results in the delocalization of the π electrons over the ring carbons. The resonance interaction between the...
02:28Electrophiles
This lesson explains the definition, classification, and characteristic features of an electrophile that are key features of nucleophilic substitution reactions. An analysis of their charge and orbital picture helps understand their reactivity for seeking electrons. Electrophiles can be classified into positive and neutral species. Other classes include free radicals and polar functional groups.
While a positive electrophile, like a proton, reacts due to its vacant, low-energy 1s orbital, the...
While a positive electrophile, like a proton, reacts due to its vacant, low-energy 1s orbital, the...
01:13Electrophilic 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.
01:15Electrophilic Aromatic Substitution: Chlorination and Bromination of Benzene
Chlorination and bromination are important classes of electrophilic aromatic substitutions, where benzene reacts with chlorine or bromine in the presence of a Lewis acid catalyst to give halogenated substitution products. A Lewis acid such as aluminium chloride or ferric chloride catalyzes the chlorination, and ferric bromide catalyzes the bromination reactions. During the bromination of alkenes, bromine polarizes and becomes electrophilic. However, in the bromination of benzene, the bromine...