Solvation effects in acidity function studies.

Much of the theoretical foundation of modern organic chemistry is based upon observations of the effect of changing molecular structure upon acid-base equilibria of many types of organic compounds. For many years after Hammett introduced it the concept of the acidity function, Ho, as an unique extension of the pH scale to concentrated acid solutions remained a useful and satisfactory way of treating strong acidic systems. However, evidence has accumulated from recent work to indicate that a single scale probably does not exist even for indicator bases of fairly similar structure. This is corroborated by the present work in which the basic strengths of carbonyl and thiocarbonyl compounds such as acids, amides, and thioureas have been determined spectrophotometically