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Tautomerism, dynamic properties and level crossing in 2‐(pyridin‐2‐yl) furan‐3‐ol by density functional theory and natural bond orbital analysis
Author(s) -
Tavakol Hossein
Publication year - 2012
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1939
Subject(s) - tautomer , chemistry , furan , density functional theory , computational chemistry , transition state theory , ring (chemistry) , bond length , reaction rate constant , crystallography , stereochemistry , organic chemistry , quantum mechanics , physics , kinetics , crystal structure
2‐(Pyridin‐2‐yl)furan‐3‐ol (PYFO, T1) and (2 E )‐2‐(pyridin‐2(1 H )‐ylidene)furan‐3(2 H )‐one (PYFO, T2) were considered to study their tautomerism interconversions, relative rotations of rings, OH bond rotations, and possibility of crossing between those energy surfaces using density functional theory methods at the Becke, three‐parameter, Lee–Yang–Parr/6‐311++G** level of theory. The optimized structures of both tautomers and the transition state of tautomerism are completely planar. A study of tautomerism in PYFO shows that T1 tautomer is about 24.38 kJ/mol more stable than T2. The rate constants of tautomerism interconversion for converting T1 to T2 is 1.98 × 10 8 M –1 s –1 and for converting T2 to T1 is 3.70 × 10 12 M –1 s –1 at room temperature that show the possibility of this tautomerism with high rate at ambient temperature. Rotation of OH bond in T1 shows two minimum (at 0° (global minimum) and 180° (local minimum)) and a transition state at 110° (and 265°) with 47.10 kJ/mol barrier energy. Relative rotation of rings shows global minimum at 0° for both tautomers and local minimum at 154° and 206° for T1 and 180° for T2. The barrier energy for ring rotation of T1 was observed at 90° and 270° with 63.69 kJ/mol height and for T2 was observed at 120 with 170.86 kJ/mol height. Interestingly, the energy levels of ring rotations for T1 and T2 are the same and crossing between them was observed. Therefore, although these two potentials do not have the same symmetries, because of the crossing between their energy level, crossing is not avoided. Copyright © 2011 John Wiley & Sons, Ltd.