Jove
Visualize
Contact Us
JoVE
x logofacebook logolinkedin logoyoutube logo
ABOUT JoVE
OverviewLeadershipBlogJoVE Help Center
AUTHORS
Publishing ProcessEditorial BoardScope & PoliciesPeer ReviewFAQSubmit
LIBRARIANS
TestimonialsSubscriptionsAccessResourcesLibrary Advisory BoardFAQ
RESEARCH
JoVE JournalMethods CollectionsJoVE Encyclopedia of ExperimentsArchive
EDUCATION
JoVE CoreJoVE BusinessJoVE Science EducationJoVE Lab ManualFaculty Resource CenterFaculty Site
Terms & Conditions of Use
Privacy Policy
Policies

Related Concept Videos

meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H01:13

meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H

6.6K
All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive toward electrophilic substitution. For example, the nitration of nitrobenzene is 100,000 times slower than that of benzene because of the deactivating effect of the nitro group. The first step in an electrophilic aromatic substitution is the addition of an electrophile to form a resonance-stabilized carbocation. The energy diagrams for...
6.6K
2° Amines to N-Nitrosamines: Reaction with NaNO201:20

2° Amines to N-Nitrosamines: Reaction with NaNO2

5.4K
Secondary amines react with nitrous acid to form N-nitrosamines, as depicted in Figure 1. Nitrous acid, a weak and unstable acid, is formed in situ from an aqueous solution of sodium nitrite and strong acids, such as hydrochloric acid or sulfuric acid, in cold conditions. In the presence of an acid, the nitrous acid gets protonated. The subsequent loss of water results in the formation of the electrophile known as nitrosonium ion.
5.4K
SN2 Reaction: Kinetics02:14

SN2 Reaction: Kinetics

10.2K
Kinetic Studies and Significance
In a chemical reaction, a relationship exists between the concentration of reactants and the rate at which the reaction proceeds. The study to measure this relationship is known as the kinetics of a chemical reaction. Kinetic studies are used to deduce the rate law of a chemical reaction, which provides information about the species involved during the transition state of the rate-determining step. Thus, kinetic studies help to derive the mechanism of a...
10.2K
SN2 Reaction: Mechanism02:27

SN2 Reaction: Mechanism

17.1K
The kinetic studies of SN2 reactions suggest an essential feature of its mechanism: it is a single-step process without intermediates. Here, both the nucleophile and the substrate participate in the rate-determining step.
The presence of the more electronegative halogen in the substrate creates a polarized carbon-halide bond. The halide pulls the electron cloud generating an electrophilic center at the carbon atom. Thus, the carbon atom carries a partial positive charge while the halide has a...
17.1K
SN2 Reaction: Transition State02:26

SN2 Reaction: Transition State

11.7K
An SN2 reaction of an alkyl halide is a single-step process in which bond formation between the nucleophile and the substrate and bond breaking between the substrate and the halide occurs simultaneously through a transition state without forming an intermediate.
When the nucleophile approaches the electrophilic carbon with its lone pairs, the halide acts as a leaving group and moves away with the electron-pair bonded to the carbon. Dotted partial bonds represent the bonds being formed or broken...
11.7K
SN2 Reaction: Stereochemistry02:23

SN2 Reaction: Stereochemistry

11.6K
In an SN2 reaction, the nucleophilic attack on the substrate and departure of the leaving group occurs simultaneously through a transition state. As the nucleophile approaches the substrate from the back-side, the configuration of the substrate carbon changes from tetrahedral to trigonal bipyramidal and then back to tetrahedral, leading to an inversion in the configuration of the product.
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not...
11.6K

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by
Same author

Quantum Trajectory Separation and Attosecond Mapping in Liquid High-Harmonic Generation.

Physical review letters·2026
Same author

Combination of ivermectin and metformin promotes autophagy in MCF‑7 cells by inhibiting phosphorylation of the PI3K/AKT/mTOR pathway.

Oncology reports·2026
Same author

Real-Time Time-Dependent Density Functional Theory Simulations with Range-Separated Hybrid Functionals for Periodic Systems.

Journal of chemical theory and computation·2026
Same author

Establishment and characterization of primary canine mammary epithelial cells as a normal-like epithelial reference model.

Research in veterinary science·2026
Same author

Polyethylene microplastics specifically drive the dissemination of ARGs: Mechanisms involving microbial community restructuring and horizontal gene transfer.

The Science of the total environment·2026
Same author

Generation of multi-μJ few-cycle blue self-compressed soliton pulses in large-core hollow-capillary fibers.

Optics letters·2026

Related Experiment Video

Updated: Jan 22, 2026

Measuring Material Microstructure Under Flow Using 1-2 Plane Flow-Small Angle Neutron Scattering
09:08

Measuring Material Microstructure Under Flow Using 1-2 Plane Flow-Small Angle Neutron Scattering

Published on: February 6, 2014

14.8K

Intrinsic High Chern Numbers in Two-Dimensional M_{2}X_{2} Materials.

Zujian Dai1,2, Xudong Zhu2, Lixin He1,2,3

  • 1University of Science and Technology of China, Laboratory of Quantum Information, Hefei 230026, China.

Physical Review Letters
|January 20, 2026
PubMed
Summary
This summary is machine-generated.

Monolayer M₂X₂ compounds exhibit distinct quantum anomalous Hall phases with varying Chern numbers (C=1 or C=2). This is explained by two generic band-inversion mechanisms based on orbital composition and symmetry, guiding the engineering of high-Chern-number insulators.

More Related Videos

Production of Human Neurogenin 2-Inducible Neurons in a Three-Dimensional Suspension Bioreactor
07:21

Production of Human Neurogenin 2-Inducible Neurons in a Three-Dimensional Suspension Bioreactor

Published on: March 17, 2023

2.0K
Exfoliation and Analysis of Large-area, Air-Sensitive Two-Dimensional Materials
10:18

Exfoliation and Analysis of Large-area, Air-Sensitive Two-Dimensional Materials

Published on: January 5, 2019

12.5K

Related Experiment Videos

Last Updated: Jan 22, 2026

Measuring Material Microstructure Under Flow Using 1-2 Plane Flow-Small Angle Neutron Scattering
09:08

Measuring Material Microstructure Under Flow Using 1-2 Plane Flow-Small Angle Neutron Scattering

Published on: February 6, 2014

14.8K
Production of Human Neurogenin 2-Inducible Neurons in a Three-Dimensional Suspension Bioreactor
07:21

Production of Human Neurogenin 2-Inducible Neurons in a Three-Dimensional Suspension Bioreactor

Published on: March 17, 2023

2.0K
Exfoliation and Analysis of Large-area, Air-Sensitive Two-Dimensional Materials
10:18

Exfoliation and Analysis of Large-area, Air-Sensitive Two-Dimensional Materials

Published on: January 5, 2019

12.5K

Area of Science:

  • Condensed Matter Physics
  • Materials Science
  • Quantum Phenomena

Background:

  • Monolayer M₂X₂ compounds share a common lattice structure but exhibit distinct quantum anomalous Hall (QAH) phases.
  • The underlying mechanisms for these distinct Chern numbers (C) are not fully understood.
  • Exploring these mechanisms is crucial for understanding and engineering topological materials.

Purpose of the Study:

  • To identify and elucidate the generic band-inversion mechanisms responsible for different Chern numbers in monolayer M₂X₂ compounds.
  • To provide a unified explanation for QAH phases in related 2D systems.
  • To offer practical guidance for designing and screening materials with tunable high-Chern-number topological properties.

Main Methods:

  • First-principles calculations to investigate electronic band structures.
  • Symmetry analysis to understand topological properties.
  • Tight-binding models to capture low-energy electronic behavior.
  • Analysis of orbital composition and symmetry representations of 3d states near the Fermi level.

Main Results:

  • Two distinct band-inversion mechanisms identified, governed by orbital composition and symmetry.
  • Dominance of dₓz and d<0xE1><0xB5><0xA7>z orbitals leads to a doubly degenerate Γ-point inversion, resulting in C=1.
  • Inversions at Γ-X and Γ-Y momenta, driven by other orbital compositions, yield C=2 through additive Berry-curvature contributions.
  • The proposed mechanisms consistently explain QAH phases in various 2D systems, including LiFeSe, KTiSb, MgFeP, and Janus M₂X₂ derivatives.

Conclusions:

  • The identified band-inversion mechanisms provide a fundamental understanding of distinct Chern numbers in M₂X₂ materials.
  • This work offers practical insights for the rational design and discovery of novel topological insulators.
  • The findings pave the way for engineering materials with tunable high-Chern-number topological states for potential applications.