Title of article :
Tautomerism, hydrogen bonding and vibrational properties of 4-acetyl-3(5)-amino-5(3)-methylpyrazole Original Research Article
Author/Authors :
Andrea Szabo-Nagy، نويسنده , , Valerija I. ?e?ljevi?، نويسنده , , Attila Kovacs، نويسنده ,
Issue Information :
هفته نامه با شماره پیاپی سال 2001
Pages :
12
From page :
67
To page :
78
Abstract :
The structure and molecular vibrations of 4-acetyl-3(5)-amino-5(3)-methylpyrazole have been investigated by quantum chemical calculations and vibrational spectroscopy. The calculations predicted a predominance of the 5-amino-3-methyl form in the tautomeric equilibrium, however, the energy difference between the two tautomers is rather small, 2 kJ/mol at the B3-LYP/6-311++G** level of the theory. The most stable conformers of each tautomer are stabilized by intramolecular hydrogen bonding. This interaction plays an important role also in the tautomeric equilibrium contributing significantly to the stability of the 5-amino-3-methyl tautomer. Another characteristics of the hydrogen bonding is its strengthening effect on the conjugation of the NH2 and CO groups with the pyrazole ring. The molecular vibrations of the title compound have been analysed by means of the scaled quantum mechanical method. Using joint theoretical and experimental information the FT-IR and FT-Raman spectra of solid 4-acetyl-3-amino-5-methylpyrazole have been assigned.
Keywords :
FT-IR , Scaled quantum mechanical analysis , FT-Raman , Hydrogen bonding , DFT calculations , conformation , Tautomerism
Journal title :
Chemical Physics
Serial Year :
2001
Journal title :
Chemical Physics
Record number :
1056855
Link To Document :
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