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Title: Evidence of C−H···O Hydrogen Bonds in Liquid 4-Ethoxybenzaldehyde by NMR and Vibrational Spectroscopies
Authors: Marques, M. P. M. 
Costa, A. M. Amorim da 
Ribeiro-Claro, Paulo J. A. 
Issue Date: 31-May-2001
Publisher: American Chemical Society
Citation: The Journal of Physical Chemistry A. 105:21 (2001) 5292-5297
Serial title, monograph or event: The Journal of Physical Chemistry A
Volume: 105
Issue: 21
Abstract: Raman, FTIR, and NMR (both 13C and 17O) spectroscopies are used in a complementary way in order to study the occurrence of C−H···O intermolecular hydrogen bonds in liquid 4-ethoxybenzaldehyde (4EtOB). Additional information concerning the structure of the possible dimers is obtained through ab initio calculations, at the B3LYP/6-31G* level. The strongest evidences of the presence of C−H···O hydrogen bonds in the liquid phase arise from the temperature and solvent intensity dependence of the two bands observed in the νCO region of the vibrational spectra, as well as from the shift to low magnetic field detected for the carbonyl 17O NMR peak at higher dilutions. Further evidence is gathered from the changes observed in the νC-H vibrational modes, the 1JCH concentration dependence detected in the NMR spectra, and ab initio results. The experimental observations are consistent with the decrease of the C−H bond length upon hydrogen-bonding, as predicted for the nonstandard blue-shifting hydrogen bonds. Ab initio calculations predict several possible structures for the dimeric species, with nearly identical energies. The calculated dimerization energy is within the −5.1 to −6.5 kJ mol-1 range, considering both basis set superposition error and zero-point vibrational energy corrections, in agreement with the obtained experimental ΔH value of −5.7 ± 0.5 kJ mol-1.
ISSN: 1089-5639
DOI: 10.1021/jp0046041
Rights: openAccess
Appears in Collections:I&D QFM-UC - Artigos em Revistas Internacionais
FCTUC Química - Artigos em Revistas Internacionais

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