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E2 Reaction: Kinetics and Mechanism

E2 Reaction: Kinetics and Mechanism

SN2 substitutions and E2 eliminations of alkyl halides proceed via a concerted pathway. While the nucleophile attacks the alpha carbon in SN2 reactions, it functions as a strong base and abstracts a beta hydrogen in the E2 mechanism. The rate-limiting transition state in E2 elimination reactions is characterized by partially broken carbon–hydrogen and carbon–halogen bonds and a partially formed pi bond between the alpha and beta carbons. The beta hydrogen and halide are eliminated...

Eddy Currents

Eddy Currents

Since eddy currents occur only in conductors, magnets can separate metals from other materials. For example, in a recycling center, trash is dumped in batches down a ramp, beneath which lies a powerful magnet. Conductors in the trash are slowed by eddy currents, while nonmetals in the trash move on, separating from the metals. This works for all metals, not just ferromagnetic ones.
Other major applications of eddy currents appear in metal detectors and the braking systems of trains and roller...

E2 Reaction: Stereochemistry and Regiochemistry

E2 Reaction: Stereochemistry and Regiochemistry

Elimination reactions of alkyl halides can yield one or more alkenes depending on the specific regiochemical and stereochemical considerations. While the regiochemistry of the reaction governs the location of the double bond in the product, the stereochemical requirements often influence the geometry.
When a substrate with two different β hydrogens undergoes an E2 elimination, the presence of a strong base can yield two regioisomeric alkenes. The more-substituted alkene is the major...

E1 Reaction: Kinetics and Mechanism

E1 Reaction: Kinetics and Mechanism

Here, in contrast to the E2 reaction mechanism, we delve into the aspects of the E1 reaction mechanism, which has two steps: rate-limiting loss of the leaving group and abstraction of the beta hydrogen by a weak base. Typically, the experimental proof for the E1 mechanism is via kinetic studies or isotope studies. While the former demonstrates the first-order kinetics—the dependence of the reaction solely on substrate concentration—the latter proves the abstraction of hydrogen only...

Euchromatin

Euchromatin

E1 Reaction: Stereochemistry and Regiochemistry

E1 Reaction: Stereochemistry and Regiochemistry

One of the critical aspects of the E1 reaction mechanism, as also observed in E2, is the regiochemistry, with multiple regioisomers obtained as products. In the example discussed, the presence of water as a weak base favors elimination over substitution to generate two alkenes. Given that alkenes’ stability increases with the number of alkyl groups across the double bond, typically, E1 reactions lead to the Zaitsev product, for this is more substituted and stable than the Hofmann product.

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Related Experiment Video

Updated: May 10, 2025

Eye Irritation Test EIT for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial RhCE Tissue Model

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e_g Electron Occupancy as a Descriptor for Designing Iron Single-Atom Electrocatalysts.

Chun Pei¹, Guohua Yao^1,2, Ziguang Zhao¹

¹The Education Ministry Key Laboratory of Resource Chemistry, Shanghai Engineering Research Center of Green Energy Chemical Engineering, Shanghai Normal University, Shanghai, 200234, China.

Advanced Materials (Deerfield Beach, Fla.)

|April 28, 2025

Summary

Researchers developed iron single-atom catalysts (SACs) with tunable e_g electron occupancy. Lower occupancy significantly boosts catalytic activity for oxygen reactions, outperforming platinum catalysts and showing promise for zinc-air batteries.

Keywords:

e g occupancy electrocatalysis ordered mesoporous carbon single‐atom catalysts

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Area of Science:

Materials Science
Electrochemistry
Catalysis

Background:

Designing efficient single-atom catalysts (SACs) requires understanding structure-performance relationships.
Quantitative descriptors are crucial for optimizing SACs in electrocatalysis.

Purpose of the Study:

To establish a quantitative electronic structure-performance relationship for iron single-atom catalysts (Fe SACs).
To identify the role of e_g electron occupancy as a descriptor for catalytic activity.

Main Methods:

Synthesis of Fe SACs supported by ordered mesoporous carbon with varying e_g electron occupancy (1.7 to 0.7).
Electrochemical evaluation of catalytic activity and oxygen intermediate activation entropy.
Analysis of the rate-determining step in oxygen reduction reactions.

Main Results:

A linear correlation was found between Fe e_g electron occupancy and catalytic activity/activation entropy.
Fe SACs with e_g occupancy of 0.7 exhibited ≈28 times higher turnover frequency than those with 1.7 e_g occupancy.
The optimized Fe SAC demonstrated ≈6.3 times higher mass activity than commercial Pt/C and achieved 196.3 mW cm^-2 in zinc-air batteries.

Conclusions:

Fe e_g electron occupancy serves as a valuable descriptor for designing high-performance single-atom electrocatalysts.
Tuning e_g electron occupancy can alter reaction mechanisms and enhance catalytic efficiency.
The developed Fe SACs show potential for advanced energy storage applications like zinc-air batteries.