ISSN:
1572-9001
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The torsional barrier was calculated in the 3-21G basis set for 1-, 2-, and 5-phenylimidazole. Full geometry optimization was carried out at inter-ring torsional angles of 0°, 30°, 60°, 90°, 120°, 150°, 180°, and additional intermediate angles. All torsional potential energies were found to be symmetric with respect to the 90° conformation. The 2-phenylimidazole torsional energy exhibits a minimum at 0° (and 180°) and a maximum at 90° with a barrier height of 5.83 kcal/mol relative to the 0° conformation. The minima in the 1- and 5-phenylimidazole torsional potential energies correspond to non-planar conformations, resulting in a double-well potential with maxima at 0° (180°) and 90°. The 1-phenylimidazole minima are located at 46.5 and 133.5°; the 5-phenylimidazole minima, at 35.3 and 144.7°. In the 0° (180°) and 90° conformations, 1-phenylimidazole exhibits torsional barriers of 1.84 and 0.75 kcal/mol, respectively, relative to the energy of the 46.5° conformation. For 5-phenylimidazole, these barriers are 0.94 and 1.89 kcal/mol, relative to the energy of the 35.3° conformation. The energy of 5-phenylimidazole in the 35.3° conformation corresponds to a relative tautomeric energy difference of 1.80 kcal/mol compared to the 0° conformer of the 4-phenylimidazole tautomer.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00672881
Permalink
