In general, if the atoms that make up the ring contain heteroatoms, such rings become heterocycles, and organic compounds containing heterocycles are called heterocyclic compounds. An article called Separation of quinaldine from a ternary mixture with quinoline and isoquinoline, published in 1968, which mentions a compound: 530-66-5, Name is quinoliniumhydrogensulphate, Molecular C9H9NO4S, Application In Synthesis of quinoliniumhydrogensulphate.
The solubility relations of the monophosphate and bisulfate salts of quinaldine (I), quinoline (II), and isoquinoline (III) were studied. The solubility of the monophosphate of III in H2O at 25° is 6.7 times that of I or II. The solubility of the bisulfates of I and II was studied at 0-50° and 75-95% EtOH. At 10° and 85% EtOH, the solubility ratio of II to I is 3.8. I, 96% pure, was obtained from a mixture of I, II, and III by the following method. To 500 g. of a 1:1 mixture I (32%), II (20%), and III (40%) in MeOH was added 1 equivalent of H3PO4 (at <25°). To the precipitated salt was added just enough H2O to dissolve all of the phosphate of III. The remaining salt was decomposed in 20% NaOH yielding a 1:1 mixture of I and II. This was dissolved in 85% EtOH (1:1 ratio) and 1 equivalent of H2SO4 was added. The precipitated salt was recrystallized from 85% EtOH at 10°, decomposed with 10% base, extracted with benzene, and distilled to yield 58.8% I. As far as I know, this compound(530-66-5)Application In Synthesis of quinoliniumhydrogensulphate can be applied in many ways, which is helpful for the development of experiments. Therefore many people are doing relevant researches.
Reference:
Thiazolidine – Wikipedia,
Thiazolidine – ScienceDirect.com