论偶氮染料的偶氮-腙互变异构

Azo-hydrazone tautomerism of azo dyes

偶氮染料存在着偶氮-腙互变异构。其中包括两个概念,一是偶氮体和腙体是一对异构体,由其结构不同导致其发色和化学性能不同;二是两种异构体在满足某种条件下可以互变。对偶氮体或腙体结构的识别是研究偶氮染料结构与性能的基础。当前染料学术界和产业界对偶氮-腙互变异构有两大误识:偶氮体即腙体,两者不必加以区分;以及两者既为互变异构,则时刻处于变化中而无法进行区分。本文针对上述误识,讨论了两种异构体的结构与性能关系。一个偶氮染料的偶氮体及醌腙体是两种结构与性能,如紫外-可见光谱吸收、化学反应性能及牢度不同的化合物。通常仅以某种异构体结构为稳定状态存在,折中结构结决定了它的颜色和染色性能。两者仅在某种特定的条件下可以互相变化。这些条件取决于化合物结构、所处环境条件,如温度、溶剂、介质p H等环境因素对偶氮-腙平衡的影响。介绍了用其红外光谱、拉曼光谱、核磁波谱、质谱以及晶体的X衍射谱来确认互变异构体的方法。

There exists azo-hydazone tautomerism for azo dyes, which consists of two concepts. Both azo form and hydrazone form are a pair of isomers, but exhibit different performance due to their structures. They can transform into each other under appropriate conditions. To confirm their isomeric structure is the base for a study of the relationship between the structure and properties. There are two misleading concepts prevailing in dyestuff industrial and academic circles. The former insists that azo form and hydrazone form co-exist with no difference between these two isomers, whilst the latter believes that they can transform into each other at any moment. An investigation into the tautomers transformation was conducted and the relationship between their structures and properties was discussed. Azo form and hydrazone form of an azo compoun possess different UV-Vs spectra, chemical properties and fastness. Usually it takes one of the tautomers as the stably-existed status, which determines its color and dyeing performance. Azo form or hydrazone form only can be transformed into each other under specified conditions, which depended on their structures and environmental conditions, such as temperature, solvents, pH of media, etc. The confirmation methods of these tautomeric structure by IR,Raman, NMR, MS spectra and X ray differential spectra were introduced.