| Autor: |
Gómez-Castro, Carlos Z., Padilla-Martínez, Itzia I., García-Báez, Efrén V., Castrejón-Flores, José L., Peraza-Campos, Ana L., Martínez-Martínez, Francisco J. |
| Předmět: |
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| Zdroj: |
Molecules; Sep2014, Vol. 19 Issue 9, p14446-14460, 15p |
| Abstrakt: |
Intramolecular hydrogen bond (HB) formation was analyzed in the model compounds N-(2-benzoylphenyl)acetamide, N-(2-benzoylphenyl)oxalamate and N1,N2-bis(2-benzoylphenyl)oxalamide. The formation of three-center hydrogen bonds in oxalyl derivatives was demonstrated in the solid state by the X-ray diffraction analysis of the geometric parameters associated with the molecular structures. The solvent effect on the chemical shift of H6 [δH6(DMSO-d6)–δH6(CDCl3)] and Δδ(ΝΗ)/ΔT measurements, in DMSO-d6 as solvent, have been used to establish the energetics associated with intramolecular hydrogen bonding. Two center intramolecular HB is not allowed in N-(2-benzoylphenyl)acetamide either in the solid state or in DMSO-d6 solution because of the unfavorable steric effects of the o-benzoyl group. The estimated ΔH° and ΔS° values for the hydrogen bonding disruption by DMSO-d6 of 28.3(0.1) kJ·mol-1 and 69.1(0.4) J·mol-1·K-1 for oxalamide, are in agreement with intramolecular three-center hydrogen bonding in solution. In the solid, the benzoyl group contributes to develop 1-D and 2-D crystal networks, through C–H•••A (A = O, π) and dipolar C=O•••A (A = CO, π) interactions, in oxalyl derivatives. To the best of our knowledge, this is the first example where three-center hydrogen bond is claimed to overcome steric constraints. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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