Lewis acidElectrophilic reagent, means acceptableElectron pairSubstances (including ions, atomic groups or molecules) based onLouis(Gilbert Newton Lewis)Acid-base electron theoryDetermined by the definition of acid.Because it contains a wide range of substances, it is also called generalized acid.
Lewis acid is mostly super corrosive.Zinc chloride, which is corrosive to cellulose, is a typical example of Lewis acid corrosion.Since water is Lewis alkaline, most Lewis acids will react with water and produce hydrates with Bronsted acidity.Therefore, many aqueous solutions of Lewis acid are Bronsted acid.Lewis acid hydrates in hydrates are connected with water molecules by strong chemical bonds, so it is difficult to dry Lewis acid hydrates, that is, Lewis acid hydrates are usually separable compounds.For example, if you try to heat and dry the water in the metal chloride (Lewis acid), it will generate hydrogen chloride and its metalhydroxide。
chemical property
Electrophilic reagentOr electron acceptor is lewis acid.Lewis acid usually contains low energy LUMO (lowest unoccupied orbital), which will react with HOMO (highest occupied orbital) of Lewis base.It is different from Bronsted Lauric acid in that Lewis acid does not necessarily need protons (H+）For Lewis acid theory, all electrophilic reagents can be called Lewis acid (including H+）。Although all Bronsted Lauric acids belong to Lewis acid, in fact, the term Lewis acid mostly refers to those that do not belong to Bronsted Lauric acid.
The chemical reactivity of Lewis acid can be usedSoft and hard acid-base theoryTo judge.Scientists still do not know the general definition of "strength" of Lewis acid, because the strength of Lewis acid is related to the reaction characteristics of its unique Lewis base.A model used to predict the strength of Lewis acid based on the affinity energy of gaseous Lewis acid to fluoride ion, so that in common separable Lewis acidAntimony pentafluorideLewis acid is the most acidic.Fluoride ions are "hard" Lewis bases, chloride ions and some "soft" Lewis bases, as well as Lewis acidity in solution, which are difficult to study due to the complexity of calculation.
type
Announce
edit
There are five types of Lewis acids: simple cations (in theory, all simple cations are Lewis acids), incomplete octets (the most important kind of Lewis acids) as the electronic structure of the central atom, compounds that can expand the octets of the central atom, compounds with heavy bonds in the central atom, and elemental substances with hexagonal electronic structure.[1]
application
Announce
edit
Lewis acid has great practical significance in acid catalytic reaction of organic chemistry, such asAluminium trichloride，Boron trifluoride、Sulfur trioxideandFerric bromideWait until Lewis acid is importantacid catalyst 。They can replace Bronsted acid catalysts (such as sulfuric acid and hydrogen fluoride, etc.) in many reactions, and their catalytic performance is often superior to Bronsted acid, and even some acid catalyzed reactions have been proved powerless with Bronsted acid, while Lewis acid can achieve immediate effect.[1]
