What is Lewis's acid?
The term Lewis acid is named after American chemist Gilbert N. Lewis. Early chemists have recognized acid as a substance with an acidic taste that reacts with some metals and neutralizes bases or alkalics and produces salt. Since the end of the 19th century, however, attempts to define acids and bases have been made in a stricter way and one that explains what is actually happening in response to acid -based. Lewis's is the widest definition. Ions H +, which are simply protons - are too reactive to exist in aqueous solution and connect with water molecules to form hydronia ions (H 3 +). The definition of Arrhenius has proved to be very useful and covers most of the compounds commonly considered as acid. For example, hydrochloric acid, a solution of gas chlorine in water provides ions h + , which form hydronic ions in solution: HCl + H 2 o → h This definition remained stAndard until the 20th century and is often used to this day.
Defining the characteristics of all acids is that they neutralize the bases for salt production. An example is the reaction of hydrochloric acid with sodium hydroxide (NaOH) to produce sodium chloride and water (H 2 ): H 3 CL SUP>--------- H 2 O. Here, the ions of H + provided by hydrochloric acid were combined with oh ions
In 1923, two chemists - Johanes Breted and Thomas Lowry - came independently. They suggested that acid was a donor donor and a proton base. In response to acid -based acid, proton or h + to the base provides; However, neither reactant may be in solution, with h + or oh - ions in fact before reaction. This definition includes all arrhenium acids and bases, but also explains a combination of hydrogen chloride and ammonia as an acid -based response: covalent chloride chloride provided ammonia proton for the formation of amonia (nh +>) Ion, which forms an Ionian combination with CL .
American chemist Gilbert N. Lewis also designed, also in 1923, a widespread concept of acids and foundations such as acceptors of electrons and donors. According to this definition, it includes reactions based on reactants acid forming a coordinate binding-capital binding, where both shared electrons come from the same atom-electrons from the base. In the reaction described above, the HC1-Nnaoh receives ion h + HCL provided a few electrons from the ions of OH - provided for water for water.
According to this theory, the Lewis base is a compound that has an undamaged electron pair for gluing. The structure of Lewis acid is such a stable configuration by creating a coordinated bond with the Lewis base. The bases do not have to contain hydroxide ions or to receive protons and Lewis acid does not have to contain hydrogen or donate protons. The definition of Lewis acid includesAll ARRHENIUS and BROFROV-LOWRY acids, as well as many substances that do not meet the BROFRED-LOWRY or Arrhenius criteria.
A good example of such a substance is boron trifluoride (BF 3 ). In this compound he created a Boron, which usually has three electrons, covalent bonds in his outer shell and shares a few electrons with each of the three fluorine atoms. Although the compound is stable, it has space for two more electrons in its outer cloak. It can therefore form a coordinating binding with an electron pair-only words, a base.
For example, it can be combined with ammonia (NH 3 ), which has a nitrogen atom with a pair of electrons, because three of the five electrons in the outer shell of nitrogen are nitural bonds with three hydrogen atoms. The combination of pine trifluoride and ammonia is therefore as follows: bf 3 +: NH 3 → bf 3