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Related Concept Videos

Halogenation of Alkenes02:46

Halogenation of Alkenes

Halogenation is the addition of chlorine or bromine across the double bond in an alkene to yield a vicinal dihalide. The reaction occurs in the presence of inert and non-nucleophilic solvents, such as methylene chloride, chloroform, or carbon tetrachloride.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
Electrophilic 1,2- and 1,4-Addition of HX to 1,3-Butadiene01:17

Electrophilic 1,2- and 1,4-Addition of HX to 1,3-Butadiene

The electrophilic addition of hydrogen halides such as HBr to alkenes and nonconjugated dienes gives a single product as per Markovnikov’s rule.
Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
¹H NMR: Complex Splitting01:13

¹H NMR: Complex Splitting

A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule02:17

Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule

If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
Regioselectivity of Electrophilic Additions-Peroxide Effect02:35

Regioselectivity of Electrophilic Additions-Peroxide Effect

In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.

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Updated: Jun 4, 2026

Coulomb Explosion Imaging as a Tool to Distinguish Between Stereoisomers
08:51

Coulomb Explosion Imaging as a Tool to Distinguish Between Stereoisomers

Published on: August 18, 2017

Multireference configuration interaction study of bromocarbenes.

Jean M Standard1, Rebecca J Steidl, Matthew C Beecher

  • 1Department of Chemistry, Illinois State University, Normal, Illinois 61790-4160, USA. standard@ilstu.edu

The Journal of Physical Chemistry. A
|February 2, 2011
PubMed
Summary
This summary is machine-generated.

This study used multireference configuration interaction (MRCI) calculations to investigate bromocarbenes. The research provides detailed electronic state properties and transition energies for these important chemical species.

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Synthesis of a Borylated Ibuprofen Derivative Through Suzuki Cross-Coupling and Alkene Boracarboxylation Reactions

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Last Updated: Jun 4, 2026

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Area of Science:

  • Quantum Chemistry
  • Computational Chemistry
  • Spectroscopy

Background:

  • Carbenes are reactive intermediates with diverse applications.
  • Brominated carbenes are of particular interest due to their unique electronic properties.
  • Understanding their electronic structure is crucial for predicting reactivity and spectroscopic behavior.

Purpose of the Study:

  • To perform high-level theoretical calculations on a series of bromocarbenes.
  • To determine equilibrium geometries and vibrational frequencies for key electronic states.
  • To compute singlet-triplet gaps and singlet-singlet transition energies.

Main Methods:

  • Multireference configuration interaction (MRCI) calculations.
  • Utilized correlation consistent basis sets of valence triple-ζ plus polarization quality.
  • Employed a full-valence active space (18 electrons in 12 orbitals).

Main Results:

  • Obtained equilibrium geometries and harmonic vibrational frequencies for X(1A'), ã((3)A''), and Ã((1)A'') states.
  • Calculated singlet-triplet gaps (ã((3)A'') ← X((1)A')) and transition energies (Ã((1)A'') ← X((1)A')).
  • Provided a consistent, high-level theoretical dataset for CHBr, CFBr, CClBr, CBr(2), and CIBr.

Conclusions:

  • The MRCI calculations offer a reliable and comprehensive theoretical foundation for bromocarbene research.
  • Results are comparable to existing experimental and computational data, validating the methodology.
  • This work serves as a valuable reference for future studies on halogenated carbenes.