Search results
Results from the WOW.Com Content Network
Boron trifluoride is a versatile Lewis acid that forms adducts with such Lewis bases as fluoride and ethers: CsF + BF 3 → Cs[BF 4] O(CH 2 CH 3) 2 + BF 3 → BF 3 ·O(CH 2 CH 3) 2. Tetrafluoroborate salts are commonly employed as non-coordinating anions.
It is a colorless liquid, although older samples can appear brown. The compound is used as a source of boron trifluoride in many chemical reactions that require a Lewis acid. [1] The compound features tetrahedral boron coordinated to a diethylether ligand. [2] Many analogues are known, including the methanol complex.
Lewis structure of a water molecule. Lewis structures – also called Lewis dot formulas, Lewis dot structures, electron dot structures, or Lewis electron dot structures (LEDs) – are diagrams that show the bonding between atoms of a molecule, as well as the lone pairs of electrons that may exist in the molecule.
An example of a dative covalent bond is provided by the interaction between a molecule of ammonia, a Lewis base with a lone pair of electrons on the nitrogen atom, and boron trifluoride, a Lewis acid by virtue of the boron atom having an incomplete octet of electrons. In forming the adduct, the boron atom attains an octet configuration.
The most common Lewis bases are anions. The strength of Lewis basicity correlates with the pK a of the parent acid: acids with high pK a 's give good Lewis bases. As usual, a weaker acid has a stronger conjugate base. Examples of Lewis bases based on the general definition of electron pair donor include: simple anions, such as H − and F −
The molecule adopts a structure similar to that of ethane, with which it is isoelectronic. The B−N distance is 1.58(2) Å. The B−H and N−H distances are 1.15 and 0.96 Å, respectively. Its similarity to ethane is tenuous since ammonia borane is a solid and ethane is a gas: their melting points differing by 284 °C.
Tris(pentafluorophenyl)borane, sometimes referred to as "BCF", is the chemical compound (C 6 F 5) 3 B.It is a white, volatile solid. The molecule consists of three pentafluorophenyl groups attached in a "paddle-wheel" manner to a central boron atom; the BC 3 core is planar.
Two common modes of Lewis acid catalysis in reactions with polar mechanisms. In reactions with polar mechanisms, Lewis acid catalysis often involves binding of the catalyst to Lewis basic heteroatoms and withdrawing electron density, which in turn facilitates heterolytic bond cleavage (in the case of Friedel-Crafts reaction) or directly activates the substrate toward nucleophilic attack (in ...