Synthesis and spectroanalytical studies of a new heterocyclic acid–base indicator
作者:Samira Razmara、Mehdi Pordel、Mahmoud Ebrahimi
DOI:10.1007/s10593-015-1764-8
日期:2015.8
view of its possible use as an indicator. The results show that this dye is an amphoteric substance with two ionization constants K a1 and K a2 indicative of weak basic and acidic properties. The pK a1 and pK a2 values in aqueous solution determined by spectrophotometric method are 2.43 and 9.73, respectively. A comparison was made with existing acid–base indicators effective over the same pH range
通过6-氯-3-硝基咪唑并[1,2- a ]吡啶与芳基乙腈在碱性MeOH溶液中通过氢原子的亲核取代反应,合成了咪唑并吡啶系列的新紫色染料。将所得的2-芳基-2- [6-氯-3-(羟基亚氨基)咪唑并[1,2 - a ]吡啶-2(3 H)-亚丙基)]乙腈进一步转化为新的8-氯吡啶并[2', 1′:2,3]咪唑并[4,5 - b ]-喹啉-12-腈。2- [6-氯-3-(羟基亚氨基)咪唑并[1,2 - a ]吡啶-2(3 H)-亚烷基)]-2-(4-甲基苯基)乙腈由于添加酸或碱而经历可再现的颜色变化。对该染料进行了紫外-可见光谱表征和酸碱平衡研究,目的是将其用作指示剂。结果表明,这种染料是两性物质,具有两个电离常数K a1和K a2,指示弱的碱性和酸性。通过分光光度法测定的水溶液中的p K a1和p K a2值分别为2.43和9.73。比较了在相同pH范围内有效的现有酸碱指示剂。