Researches on sulphanilamide, para‐amino‐benzoic acid and their derivatives. III: Ultraviolet absorption spectra and potentiometric titrations

Abstract

With the aim of providing more facts for the discussion of the mode of action of the sulphonamides and of p‐aminobenzoic acid, the ultraviolet absorption spectra are recorded for a number of sulphanilamide derivatives, p‐aminobenzoic acid and related compounds. Moreover their electrochemical properties are determined by potentiometric titration. The results obtained permit a more detailed discussion of the state of these molecules in neutral solution, of the differences between p‐aminobenzoic acid and its isomers and of those between sulphanilamide and its heterocyclic derivatives. Furthermore the separate position of compounds like p‐aminomethylbenzoic acid and of p‐aminomethyl‐benzenesulphonamide (Marfanil) is clearly indicated.

Catiomers and aniomers: unique classes of isomeric ions

“…This term was not coined by us but has a long history in organic chemistry [15] and gas-phase ion chemistry. [16] In the 1950s, but as far as we could verify as early as 1947, [17] organic chemists started to use the term protomers to describe isomeric forms of a protonated molecule in rapid equilibrium in solution. These studies exemplify the role of the term protomers in the early development of quantitative concepts of bonding, and much of the current knowledge of structure-stability relationships is derived from these studies.…”