Tautomerism in 4-hydroxypyrimidine, S-methyl-2-thiouracil, and 2-thiouracil.
The keto-enol tautomerism of 4-hydroxypyrimidine and of the related molecules S-methyl-2-thiouracil and 2-thiouracil has been investigated using synchrotron-based techniques. The populations of the constituent tautomers and thermodynamic parameters have been obtained by analysis of core-level photoemission spectra. The effect of substituents on the stability of tautomers has been revealed. Attaching additional OH (or SH) groups to the aromatic ring stabilizes the dioxo (or oxo-thione) forms. However, substitution of hydrogen in position 2 by an S-CH(3) group (that is, in going from 4-hydroxypyrimidine to S-methyl-2-thiouracil) does not significantly affect the tautomeric equilibrium.
Departamento de Química da Universidade de Coimbra, 3004-535 Coimbra, Portugal.
Barbara M
BM
Giuliano
Vitaliy
V
Feyer
Kevin C
KC
Prince
Marcello
M
Coreno
Luca
L
Evangelisti
Sonia
S
Melandri
Walther
W
Caminati
D015394:Molecular Structure; D011744:Pyrimidinones / Q000737:chemistry*; D013237:Stereoisomerism; D013816:Thermodynamics; D013889:Thiouracil / Q000031:analogs & derivatives* / Q000737:chemistry*
D011744:Pyrimidinones; C108140:4-hydroxypyrimidine; D013889:Thiouracil