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Evaluation of the origin of conformational and tautomeric preferences in N ‐formylformamide – A quantum chemical study
Author(s) -
Nowroozi A.,
Mohammadzadeh Jahani P.,
Asli N.,
Hajiabadi H.,
Dahmardeh S.,
Raissi H.
Publication year - 2011
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.23000
Subject(s) - tautomer , natural bond orbital , chemistry , intramolecular force , computational chemistry , ab initio , hydrogen bond , basis set , conformational isomerism , molecule , amide , density functional theory , stereochemistry , organic chemistry
Quantum chemical study of N ‐formylformamide (NFF) was carried out at various theoretical levels and the determinate equilibrium conformations were recomputed at the high level ab initio methods such as G2MP2, G2, G3, and complete basis set (CBS)‐QB3. The computational results reveal that the amide resonance and intramolecular hydrogen bonding are two superior factors in determining the most stable conformation of diamide (DA) and amide–imidic (AI) acid tautomers, respectively. The evaluation of hydrogen bond energies predicts that the hydrogen bond (HB( strength of NFF is weaker than the malonaldehyde (MA). But the results of atoms in molecules (AIM(, natural bond orbital (NBO), and geometrical parameters are given a different order, E HB (NFF) > E HB (MA). Although the bond average energies of tautomerization process emphasized on more stability of AI tautomer, but our theoretical calculations reveal that the DA conformers are more stable than the AI ones. The population analyses of equilibrium conformations by NBO method also predict that the origin of tautomeric preference is mainly because of the electron delocalization of amide functional group, especially LP(N)→ π* CO charge transfer. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2012