The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Infrared spectra of derivatives of pyrimidine》. Authors are Short, L. N.; Thompson, H. W..The article about the compound:6-Hydroxy-2-methylpyrimidin-4(3H)-onecas:1194-22-5,SMILESS:CC1=NC(=CC(N1)=O)O).Name: 6-Hydroxy-2-methylpyrimidin-4(3H)-one. Through the article, more information about this compound (cas:1194-22-5) is conveyed.
Graphs of the vibrational spectra between 2 and 25 μ are given for the following compounds suspended as solids in paraffin or perfluorokerosine, and for the deuterio derivatives of the starred compounds (deuteriated by treatment with D2O): pyrimidine, monosubstituted pyrimidines: 2-Cl-, 2-NH*2-, 5-NH2-2-OH-*, 4-OH-*, 2-SH-*; 2,4-disubstituted pyrimidines: Cl2-, (OEt)2, (OPh)2, 2-Cl-4-NH2-*, (OH)2-*, 2-OH-4-NH2-*, (NH2)2-(SH)2-*, 2-SH-4-NH2-, 2(-)SH-4-OH-*; 4,6-disubstituted pyrimidines: 4-NH2-6-Cl-*, 4-OH-6-Me-, (OH)2-, 4-OH-6NH2-*, (NH2)2-*, 2,4,6-trisubstituted pyrimidines: Cl3-, 2-Me-4,6-Cl2-, 2-NH2-4,6-Me*2-2-NH2-4,6-(OMe)2-, 2-NH2-4,6-Cl2-, 2-NH2-4-Me-6-OEt-*, 2-NH2-4-Me-6-Cl-*, 2,6-Cl2-4-NH2-, 2-Cl-4-NH2-6-Me-, 2,6-Me2-4-NH2-*, 2-Me-4-NH2-6-Cl-, 2-NHMe-4-Me-6-Cl-, 2,6-Me2-4-OH-, 2,4-(OH)2-6-Me-, 2-Me-4,6-(OH)2-, (OH)3-, 2-NH2-4-OH-6-Me-*, 2-NMe2-4-OH-6-Me-*, 2-NH2-4-OH-6-Cl-, 2-SMe-4-OH-6-NH2-, 2-Me-4-OH-6-NH2-*, (NH2)3-, 2,4-(OH)2-6-NH2-, 2-NH2-4,6-(OH)2-, 2,4-(NH2)2-6-OH, 2-OH-4,6-(NH2)2-, 2-SH-4-OH-6-Me-, 2-SH-4-OH-6-NH2-, 2-NH2-4-Me-6-CONH2-, 2-NH2-4-Me-6-CN-; also the 4-NH2-5-Ph-*, 2,4-(OH)2-5-NO2-, 4,6-(NH2)2-5-Br-, 2-Me-4,6-(OMe)2-5-NO2-, 2-Me-4,6-(OMe)2-5-NH2-, 2-SEt-4-OH-5-Et-6-Me-, 1,4-Me2-2-SMe-6-O-, 1,3-Me2-2,4-O2-, 2-NH2-3-Et-4-Me-6-O-, and 1-Et-2-NH2-4-Me-6-O- pyrimidine derivatives In the OH and NH2 pyrimidines with or without other substituents around the ring, the main regions connected with the possibility of tautomerism are at 6 μ and 3 μ. Since ambiguities occur in both these regions, exact frequency assignments are difficult to make. The spectra are highly characteristic with sharp bands and might be used for analysis and identification. The spectral evidence suggests a ketonic structure for simple 2-OH and 4-OH derivatives and probably a diketonic form for 2,4-(OH)2 derivatives In 4,6-dihydroxypyrimidine one CO and one OH group may be present. NH2-substituents are probably not tautomerized and have the character of an amido group. The electronic effects of different substituents may influence the tautomerism and the amount of H-bonding. These conclusions do not agree in some respects with those of Brownlie (C.A. 45, 2778d).
There is still a lot of research devoted to this compound(SMILES：CC1=NC(=CC(N1)=O)O)Name: 6-Hydroxy-2-methylpyrimidin-4(3H)-one, and with the development of science, more effects of this compound(1194-22-5) can be discovered.
Reference:
Oxazolidine – Wikipedia,
Oxazolidine | C3H7NO – PubChem