吡啶酮系偶氮染料腙体结构中亚胺基质子的交换和解离动力学

吡啶酮系偶氮染料腙体结构中, 亚胺基质子能与水分子中的质子发生交换和解离。用核磁双共振实验测定了交换速率(ka)和活化能(E0)。两者均与染料结构、pH值、温度、溶剂性质和水含量等因素有关。在重氮和偶合组分一的亲电取代基和溶液中的碱都能促进交换反应。本文进一步解释了该系列染料的变色机理和染料具有不同的pH值。

Kinetic of exchange and dissociation for imino proton in hydrazone form of pyridone azo dyes

Pyridone azo dyes usually exist in hydrazone form. The proton of imino group (δ3.2-4.0). The proton lifetime (τA) and activation energy (E0) can be determined by means of nuclear magnetic double resonance. It is discovered that the exchange rate (ka) and E0 are related to structure of the dyes, pH values, temperature, property of the solvents used and relative content of water in the solution. In this paper, the effect of dye structure on τA and E0 has been investigated under similar experiment conditions. It is shown that the ka can be promoted by both the electron-withdrawing substituents in diazo and coupling components. Alkali in the solution can accelerate ka and decrease E0. The colour change mechanism and different pK values of the dyes have also been further explained in this paper.