One of the most remarkable chemists of the twentieth century, Gilbert Lewis (1875–1946), who died in a rather peculiar event involving cyanide (which will figure further in this account) took the story of acids and bases that I described in Reaction 2, extended its reach, and thereby captured a further huge swathe of chemical countryside. As I remarked in that section, chemists seek patterns of behaviour, partly because it systematizes their subject but also because it gives insight into the molecular events accompanying a reaction. Lewis contributed greatly to this enlargement of chemistry’s vision, as I shall unfold in this section. I explained in Reaction 2 how Lowry and Brønsted had extended Arrhenius’s vision of acids and bases by proposing that all reactions between acids and bases involve the transfer of a proton (a hydrogen ion, H+) from the acid, the proton donor, to the base, the proton acceptor. For instance, hydrochloric acid, HCl, can provide a proton that sticks to an ammonia molecule, NH3, 1, converting it into NH4+, 2. The Lowry–Brønsted account of an acid–base reaction involves a proton as an essential part of the definition: if protons aren’t around, then Lowry and Brønsted are silent on whether a substance is an acid or a base. There are, however, many reactions that resemble acid–base reactions but in which no protons are transferred. I will give what might seem to be a rather esoteric example, but it makes the point in a simple and direct way, so please bear with me; you will soon see the relevance of this presentation to everyday life. The esoteric example I have in mind is a reaction in which a boron trifluoride molecule, BF3, 3, sticks to an ammonia molecule to form NH3BF3, 4. This reaction clearly resembles the proton transfer reaction in which H+ attaches to NH3 to form NH4+, but with BF3 playing the role of H+. Lewis brought these aspects together in a very simple idea in 1923, at about the same time as Lowry and Brønsted made their proposals. A base, he proposed, is any species that can use two of its electrons to attach to an incoming species.
Intelligent Numerical Computing Methods for Determining the Concentration of Citric Acid by Accurate Measurement and Calculation
