Ionizing properties of complexes with strong symmetrical hydrogen bonds in acid solutions in aprotic solvents

Solvated proton as the main reagent and a catalyst in the single-stage aromatic sulfonation and protodesulfonation of sulfonic acids

“…Ideas regarding the existence of Н + (Н 2 О) 6 hexahydrate in aqueous acid with a well‐defined boundary of positive charge delocalization largely coincides with the results of N. B. Librovich and G. V. Yukhnevich et al Their spectral measurements and ab initio calculations for Н 3 О + (Н 2 О) n hydrates at n = 0 to 4 have shown that Н 9 О 4 + possesses a stable structure with a linear symmetrical Н‐bond. The symmetrical hydrogen bond is several times stronger than ordinary hydrogen bonds and has a spectrum with a continuous absorption in the IR region.…”

“…The above ideas regarding the proton existing in aqueous solutions of strong acids as a hexahydrate agree with the suggestion that protonation of organic compounds in such media does not involve direct protonation of a base B forming BH + but rather the substitution of a water molecule by a basic molecule, В , in the Zundel ion, Н 5 О 2 + (core structure of the Stoyanov ion Н 13 О 6 + ), according to Equation : …”

“…In addition to the direct process of protonation in aqueous acidic solutions, reagents В tend to build complexes with ions, molecules of acids, and water . Complex formation involving a basic reagent and hydrated proton may result in the formation of hydration complexes on a larger scale (В…Н + ·nН 2 О).…”

“…The direct knowledge of the degree of solvated proton hydration influences the interpretation of the mechanisms of numerous homogeneous and heterogeneous catalytic processes, enzymatic reactions, interphase ion‐exchange protodesorption, the formation, isomerization, hydrolysis of aromatic sulfonic acids and their functional derivatives, and the proton transfer in proton‐exchange polymer membranes and in solid electrolytes of electrochemical cells . The possibility of realization of the above processes is often determined by the solubility of the substrates, particularly of aromatic hydrocarbons, sulfonic acids, and their substituted derivatives…”

“…Since the studies by Hammet, new approaches have been developed to describe the catalytic properties of aqueous acidic solutions and to determine and calculate the рK а values of acids . These require detailed evaluation.…”