The origin and development of the acidity function

Abstract

The acidity function is a thermodynamic quantitative measure of acid strength for non-aqueous and concentrated aqueous Brønsted acids, with acid strength being defined as the extent to which the acid protonates a base of known basicity. The acidity function, which was developed, both theoretically and experimentally, by Louis P. Hammett of Columbia University during the 1930s, has proven useful in the area of physical organic chemistry where it has been used to correlate rates of acid-catalyzed reactions and to quantitate the acidity of superacids, acids with protonating abilities greater than pure sulfuric acid. All Brønsted acids can now be compared using a common measure. Karl Popper's seminal idea of theory falsification does not apply here because of the many successful applications of the acidity function. Likewise, Thomas Kuhn's idea of a paradigm shift does not apply here, even though the acidity function concept was revolutionary, because the acidity function is commensurate with classical concepts of acidity.

Brønsted Acidity and the Medium: Fundamentals with a Focus on Ionic Liquids

“…To determine the Hammett acidity function of a liquid, spectrophotometric data are obtained for a series of added indicator base/acid couples and H 0 values are derived by interpolation. A history of the acidity function has been pro-vided by Pagni [132] and a critical discussion is available in the book by Rochester.…”

“…To determine the Hammett acidity function of a liquid, spectrophotometric data are obtained for a series of added indicator base/acid couples and H 0 values are derived by interpolation. A history of the acidity function has been pro-vided by Pagni [132] and a critical discussion is available in the book by Rochester. [133] Figure 2 shows the acidity function of aqueous perchloric acid from measurements with five indicators and Figure 3 is an example of the quality data that can be obtained for an indicator as a function of acidity.…”

Using a Metaverse to Teach Students to Predict the Interaction of Acids and Bases Using Hard and Soft Acids and Bases (HSAB) Theory

“…Acid–base interactions are extremely common in nature and widely used in scientific and industrial practice. − On the basis of modern theories of acids and bases, many important branches of chemistry have been developed. Some of the examples are chemistry of aqueous and nonaqueous solutions of electrolytes, , determination of pH in nonaqueous solutions, homo- and heterogeneous acid–base catalysis, the theory of acidity functions, and many others. Therefore, understanding the key principles of the acid–base behavior of atoms and molecules is essential to learning chemistry in a variety of contexts.…”

Homochirality of Organic Matter – Objective Law or Curious Incident?

“…"The best we can do is to imagine as piral or coiled current of electrons going aroundt he atomsn ucleus." [54] Accordingly, b-decay of radioactive elements generatesm ore left-rotating electrons than rightrotating.I nherent chirality also manifests itself in breaking mirror symmetry in stable atomsd uring the absorption or emissiono fl ight by hot vapors of heavy elements, such as lead, bismuth, thallium, and cesium. [55,56] Such properties,w hich are in conflict with quantum electrodynamics,s upport the theoryo fu nification of the electromagnetic and chiral weak interactions.…”