Lewis acids An electron-pair acceptor

Many of the d-block elements form characteristically colored solutions in water. For example, although solid copper(II) chloride is brown and copper(II) bromide is black, their aqueous solutions are both light blue. The blue color is due to the hydrated copper(II) ions, [Cu(H20)fJ2+, that form when the solids dissolve. As the formula suggests, these hydrated ions have a specific composition they also have definite shapes and properties. They can be regarded as the outcome of a reaction in which the water molecules act as Lewis bases (electron pair donors, Section 10.2) and the Cu2+ ion acts as a Lewis acid (an electron pair acceptor). This type of Lewis acid-base reaction is characteristic of many cations of d-block elements. 

Lewis acid An electron pair acceptor. Examples H h Fe3 BF3. 

The molecules or ions that surround the central metal ion in a coordination compound are called ligands, and the atoms that are attached directly to the metal are called ligand donor atoms. In cisplatin, for example, the ligands are NH3 and Cl-, and the ligand donor atoms are N and Cl. The formation of a coordination compound is a Lewis acid-base interaction (Section 15.16) in which the ligands act as Lewis bases (electron-pair donors) and the central metal ion behaves as a Lewis acid (an electron-pair acceptor). 

A vast generalization beyond the Bronsted—Lowry acids and bases concepts is the concept of a Lewis29 base (an electron pair donor) and a Lewis acid (an electron pair acceptor). This concept has been used extensively in all branches of chemistry. In physical organic chemistry, quantities of the type pA = —logio[A] have used extensively to study reactivities—for example, in the Hammett equation. 

Electrophile or Lewis acid, an electron pair acceptor Electron-releasing group Electron-withdrawing group Ethyl, CH3CH2... 

Lewis acid an electron pair acceptor Lewis base an electron pair donor... 

Boron trifluoride is a Lewis acid, an electron-pair acceptor. Molecular orbital theory of BF3 must provide an orbital capable of acting as such an acceptor to be consistent with this chemical property. The VSEPR-predicted shape is trigonal, consistent with experimental observations. 

The sec-butyl cation can react as both a Bronsted-Lowry acid (a proton donor) and a Lewis acid (an electron pair acceptor) in the presence of a water-sulfuric acid mixture. In each case, however, the product is different. The two reactions are as follows ... 

Le Chatelier s principle if a change is imposed on a system at equilibrium, the position of the equUibrium will shift in a direction that tends to reduce the effect of that change. (13.7) Lewis acid an electron-pair acceptor. (14.11)... 

Lewis acid An electron pair acceptor such as an electron-deficient metal on the surface of a solid-state material, which would combine with an electron pair donor (a Lewis base) such as water. 

The Friedel-Crafts procedure uses aluminium chloride, 3, to act as this dentist compound. It gets regenerated in the reaction, so it is present as a catalyst (Reaction 11). When you examine this molecule you see that although its Cl atoms are rich in electrons, the aluminium atom, Al, has a very skimpy share in them and the positive charge of its nucleus shines through. Moreover, the molecule is flat, and there is plenty of room for the Cl atoms to bend away from any incoming intruder atom and so make room for its attachment to the Al atom. These features imply that 3 can act as a Lewis acid, an electron-pair acceptor (Reaction 9) and use its attachment to the incoming atom to... 

The triiodide ion. Is , is one of a group of species called polyhalide ions that are produced by the reaction of a halide ion with a halogen molecule. In the reaction below, the F ion acts as a Lewis base (an electron-pair donor) and the I2 molecule as a Lewis acid (an electron-pair acceptor). 

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