Protonenübertragungsreaktionen zweibasischer Säuren in wäßriger Lösung: 3-Hydroxypyridin / Proton Transfer Reactions of Dibasic Acids in Aqueous Solution: 3-Hydroxypyridine

Abstract

Proton transfer in aqueous solutions of 3-hydroxypyridin (3HP) has been studied by tempera­ture jump relaxation and ultrasound absorption techniques. Two chemical relaxations have been observed. In the range pK1<pH<pK2 the slower of the two processes corresponds to proton transfer between the N and O atoms. A mechanism is proposed which describes the pH and con­centration dependence of the relaxation time measured. Proton transfer involves two types of pro­cesses which operate in parallel: I. pseudomonomolecular, by consecutive diffusion-controlled protonation and deprotonation steps, and 2. bimolecular by diffusion-controlled proton transfer between the neutral 3HP molecule and its corresponding cation or anion. There is no evidence for direct monomolecular proton transfer within the hydration shell of the molecule (k→ ~ k← < 2 × 1O3 sec-1).