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A good example is the formation of adducts between the Lewis acid borane and the oxygen atom in the Lewis bases, tetrahydrofuran (THF): BH 3 ·O(CH 2) 4 or diethyl ether: BH 3 ·O(CH 3 CH 2) 2. Many Lewis acids and Lewis bases reacting in the gas phase or in non-aqueous solvents to form adducts have been examined in the ECW model. [3]
Many adducts violate the octet rule, such as the triiodide anion: I 2 + I − → I − 3. The variability of the colors of iodine solutions reflects the variable abilities of the solvent to form adducts with the Lewis acid I 2. Some Lewis acids bind with two Lewis bases, a famous example being the formation of hexafluorosilicate: SiF 4 + 2 F ...
Non-nucleophilic. Weak. v. t. e. A frustrated Lewis pair (FLP) is a compound or mixture containing a Lewis acid and a Lewis base that, because of steric hindrance, cannot combine to form a classical adduct. [1] Many kinds of FLPs have been devised, and many simple substrates exhibit activation. [2][3] The discovery that some FLPs split H 2[4 ...
Boron trifluoride is a versatile Lewis acid that forms adducts with such Lewis bases as fluoride and ethers: CsF + BF3 → Cs [BF4] O (CH 2 CH 3) 2 + BF3 → BF3·O (CH2CH3)2. Tetrafluoroborate salts are commonly employed as non-coordinating anions.
Since Lewis adducts are formed by dative bond between Lewis bases and Lewis acids, the orbital overlap between the Lewis base and σ*(Sb–X) orbital is the source of the acidity. According to Gabbaï et al., NBO analysis of the Sb(C 6 F 5) 3 P(O)Ph 3 adduct indicates a donor-acceptor interaction between lp(O) and σ*(Sb–C 6 F 5). [7] [8]
Lewis acid catalysis. In Lewis acid catalysis of organic reactions, a metal-based Lewis acid acts as an electron pair acceptor to increase the reactivity of a substrate. Common Lewis acid catalysts are based on main group metals such as aluminum, boron, silicon, and tin, as well as many early (titanium, zirconium) and late (iron, copper, zinc ...
In these adducts, the boron center is no longer trigonal planar and no longer has its empty p orbital that participates in conjugation in the π system in 9-borafluorene. Adducts involving Lewis bases such as pyridines, phosphines, ethers, carbenes, and nitriles have been described. The reactions involve simple reaction of the 9-borafluorene ...
Michael addition reaction. In organic chemistry, the Michael reaction or Michael 1,4 addition is a reaction between a Michael donor (an enolate or other nucleophile) and a Michael acceptor (usually an α,β-unsaturated carbonyl) to produce a Michael adduct by creating a carbon-carbon bond at the acceptor's β-carbon. [1][2] It belongs to the ...