Strength of the N-HiiiO=C and C-HiiiO=C Bonds in Formamide and N-Methylacetamide Dimers
- Pacific Northwest National Laboratory
- Universidad Autonoma Metropolitana
- Columbia University
- COLUMBIA UNIVERSITY
- BATTELLE (PACIFIC NW LAB)
The structures of the dimers of formamide and N-methylacetamide have been calculated at the ab initio electronic structure theory level, 2nd order Miller-Plesset perturbation theory (MP2) with augmented correlation consistent basis sets. Five unique structures were optimized for the formamide dimers at the MP2/aug-cc-pVDZ and MP2/aug-cc-pVTZ levels. At the optimized geometries obtained with the aug-cc-pVTZ basis set, MP2 energies were evaluated with the aug-cc-pVQZ basis set allowing an extrapolation of the energies to the complete basis set limit. Four structures were found for the N-methylacetamide dimer at the MP2/aug-cc-pVDZ level and single point energies were calculated at the MP2/aug-cc-pVTZ level. In both systems, the basis set superposition error (BSSE) was estimated with the counterpoise method. The strength of the N-HiiiO=C bond has a mean value of 7.1 kcal/mol in the formamide dimers and a mean value of 8.6 kcal/mol in the N-methylacetamide dimers. The difference in hydrogen bond strengths is attributed to differences in basicity at the carbonyl oxygen receptor site. In several dimers C-HiiiO=C hydrogen bonds play an important role in stabilizing these intermolecular complexes increasing the interaction energy by 1.1 to 2.6 kcal/mol per interaction.
- Research Organization:
- Pacific Northwest National Lab., Richland, WA (US), Environmental Molecular Sciences Laboratory (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 15004989
- Report Number(s):
- PNNL-SA-33725; 1796; KP1301030; TRN: US200321%%283
- Journal Information:
- Journal of Physical Chemistry A, Vol. 105, Issue 20; Other Information: PBD: 24 May 2001
- Country of Publication:
- United States
- Language:
- English
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