|
Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT
| ABSTRACT - Internet Electron. J. Mol. Des. April 2004, Volume 3, Number 4, 163-181 |
Tautomerism and Non-planarity of the Amino Group in 4(7)-Aminobenzimidazole:
A Theoretical and Matrix-isolation FT-IR Study
Linda Houben, Riet Ramaekers, Ludwik Adamowicz, and Guido Maes
Internet Electron. J. Mol. Des. 2004, 3, 163-181
|
Abstract:
The tautomeric equilibrium 4-NH2-benzimidazole ↔
7-NH2-benzimidazole has been investigated using a combined
theoretical (DFT (B3LYP)/6-31++G**) and experimental
(matrix-isolation FT-IR) methodology. The 4-NH2 tautomer
appears to be the most abundant form in a low temperature Ar
matrix in accordance with the theoretical predictions. The rare
7-NH2 form is sufficiently abundant to be vibrationally
characterized in detail. The obtained results have allowed to
analyze the non-planarity of the NH2 group, which is particularly
large in the 7-NH2 tautomer. This appears to be at the origin of a
large deviation between predicted and experimental frequencies
of the NH2 wag mode. The latter effect has also been observed
for other compounds with a NH2 group in close proximity of an
N-H group.
|