The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Solubility of the quinoline and isoquinoline acid sulfates in ethyl alcohol》. Authors are Potashnikov, M. M.; Gorelov, P. N..The article about the compound:quinoliniumhydrogensulphatecas:530-66-5,SMILESS:[O-]S(=O)(O)=O.C12=CC=C[NH+]=C1C=CC=C2).Reference of quinoliniumhydrogensulphate. Through the article, more information about this compound (cas:530-66-5) is conveyed.
The solubility of the acid sulfates of quinoline (I) and isoquinoline (II) in 75-95% EtOH was determined for the temperature range 0-50°. The exptl. data show that crystalline hydrates are formed in ∼85% EtOH (C9H7N.H2SO4.4H2O at 0-15°; 2C9H7N.H2SO4.7H2O at 15-20°). I is 2-3 times as soluble in EtOH as is II and this fact can be used to sep. the 2 compounds
There are many compounds similar to this compound(530-66-5)Reference of quinoliniumhydrogensulphate. if you want to know more, you can check out my other articles. I hope it will help you，maybe you’ll find some useful information.
Reference:
Thiazolidine – Wikipedia,
Thiazolidine – ScienceDirect.com