Related Concept Videos
01:29Covalent Bonds
When two atoms share electrons to complete their valence shells they create a covalent bond. An atom’s electronegativity—the force with which shared electrons are pulled towards an atom—determines how the electrons are shared. Molecules formed with covalent bonds can be either polar or nonpolar. Atoms with similar electronegativities form nonpolar covalent bonds; the electrons are shared equally. Atoms with different electronegativities share electrons unequally, creating polar bonds.A Covalent...
01:24Van der Waals Interactions
Atoms and molecules interact with each other through intermolecular forces. These electrostatic forces arise from attractive or repulsive interactions between particles with permanent, partial, or temporary charges. The intermolecular forces between neutral atoms and molecules are ion–dipole, dipole–dipole, and dispersion forces, collectively known as van der Waals forces.Polar molecules have a partial positive charge on one end and a partial negative charge on the other end of the molecule,...
02:46Covalent Bonding and Lewis Structures
Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual attraction of atoms for a “shared” pair of electrons.
02:54Lewis Structures of Molecular Compounds and Polyatomic Ions
To draw Lewis structures for complicated molecules and molecular ions, it is helpful to follow a step-by-step procedure as outlined:
01:10Van der Waals Equation
The ideal gas law is an approximation that works well at high temperatures and low pressures. The van der Waals equation of state (named after the Dutch physicist Johannes van der Waals, 1837−1923) improves it by considering two factors.
First, the attractive forces between molecules, which are stronger at higher densities and reduce the pressure, are considered by adding to the pressure a term equal to the square of the molar density multiplied by a positive coefficient a. Second, the volume...
First, the attractive forces between molecules, which are stronger at higher densities and reduce the pressure, are considered by adding to the pressure a term equal to the square of the molar density multiplied by a positive coefficient a. Second, the volume...
01:08Covalent Bonds
Overview
When two atoms share electrons to complete their valence shells, they create a covalent bond. An atom's electronegativity—the force with which shared electrons are pulled towards an atom—determines how the electrons are shared. Molecules formed with covalent bonds can be either polar or nonpolar. Atoms with similar electronegativities form nonpolar covalent bonds; the electrons are shared equally. Atoms with different electronegativities share electrons unequally, creating polar bonds.
When two atoms share electrons to complete their valence shells, they create a covalent bond. An atom's electronegativity—the force with which shared electrons are pulled towards an atom—determines how the electrons are shared. Molecules formed with covalent bonds can be either polar or nonpolar. Atoms with similar electronegativities form nonpolar covalent bonds; the electrons are shared equally. Atoms with different electronegativities share electrons unequally, creating polar bonds.
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06:53
Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F−
Published on: July 27, 2018
Boryllithium: isolation, characterization, and reactivity as a boryl anion.
Yasutomo Segawa1, Makoto Yamashita, Kyoko Nozaki
1Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113-8656, Japan.
Science (New York, N.Y.)
|October 7, 2006
Summary
Researchers synthesized a novel nucleophilic boryllithium compound, isoelectronic with N-heterocyclic carbenes. This anionic boryl species exhibits significant basicity and nucleophilicity, opening new avenues in organoboron chemistry.
Area of Science:
- Organometallic Chemistry
- Boron Chemistry
- Synthetic Chemistry
Background:
- Nucleophilic, anionic boryl compounds are highly sought-after but remain largely undiscovered.
- Existing synthetic methods have not successfully isolated stable anionic boryl species.
Purpose of the Study:
- To synthesize and characterize a novel nucleophilic, anionic boryl compound.
- To investigate the structural and electronic properties of the synthesized boryl species.
- To evaluate the reactivity of the boryl compound as a base and nucleophile.
Main Methods:
- Reductive cleavage of a boron-bromine bond using lithium naphthalenide.
- X-ray crystallography for structural determination.
- (11)B nuclear magnetic resonance spectroscopy for electronic characterization.
Main Results:
- Successful synthesis of a boryllithium compound isoelectronic with N-heterocyclic carbenes.
- X-ray crystallography confirmed sp(2) boron hybridization and a short boron-lithium bond.
- Spectroscopic data and structural analysis indicate significant anionic charge on the boron atom.
- The boryllithium compound demonstrated efficient basicity and nucleophilicity with various electrophiles.
Conclusions:
- The study reports the first isolation of a stable nucleophilic, anionic boryl compound.
- The synthesized boryllithium serves as a valuable synthetic tool due to its reactivity.
- This discovery expands the scope of organoboron chemistry and N-heterocyclic carbene analogues.