The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《The effect of electron-withdrawing groups on 15N and 13C chemical shifts: A density functional study on a series of pyrroles》. Authors are Mothana, B.; Ban, F.; Boyd, R. J.; Thompson, A.; Hadden, C. E..The article about the compound:Ethyl 3,5-Dimethyl-2-pyrrolecarboxylatecas:2199-44-2,SMILESS:O=C(C1=C(C)C=C(C)N1)OCC).HPLC of Formula: 2199-44-2. Through the article, more information about this compound (cas:2199-44-2) is conveyed.
Electron-withdrawing groups (EWGs) on the nitrogen atom of pyrroles have significant effects on the properties of the pyrrole. It has been suggested that the exptl. 13C chem. shifts show a general increase in deshielding effect with the increase of N-EWGs strength [A. Thompson, S. Gao, G. Modzelewska, D.S. Hughes, B. Patrick, D. Dolphin, Organic Lett., 2, 3587 (2000)]. However, recently observed 15N chem. shifts of pyrroles do not correlate with the N-EWG strength. To elucidate the relationship between the electronic structures of pyrroles and their nitrogen and carbon chem. shifts, d. functional theory calculations were performed on pyrroles with various substituents. A correlation between the paramagnetic shift and the 15N chem. shift was observed for the pyrroles, indicating that the nitrogen chem. shift trend for the pyrroles arises entirely from variations of the paramagnetic shift contribution. However, a general correlation between the 15N chem. shifts and the EWG strength does not exist. Natural chem. shielding (NCS) anal. shows that the changes in the σ(N5-R)-π* transitions and changes in the sum of the σ(C1-N5)-π* and σ(C4-N5)-π* transitions account for the nitrogen chem. shift trend observed in the pyrroles.
There is still a lot of research devoted to this compound(SMILES：O=C(C1=C(C)C=C(C)N1)OCC)HPLC of Formula: 2199-44-2, and with the development of science, more effects of this compound(2199-44-2) can be discovered.
Reference:
Thiazolidine – Wikipedia,
Thiazolidine – ScienceDirect.com