Theoretical Study on Salicylaldehyde and 2-Mercaptobenzaldehyde:  Intramolecular Hydrogen Bonding

Abstract

The molecular structures and the intramolecular hydrogen bonding for salicylaldehyde and 2-mercaptobenzaldehyde have been investigated with both ab initio and density functional theory methods. We have considered the several possible conformations with respect to the rotation of two functional groups in a given molecule not only to understand the conformational behaviors but also to estimate the energy of intramolecular hydrogen bonding. The optimized geometrical parameters for salicylaldehyde at the B3LYP levels and the computed 1H NMR chemical shifts for 2-mercaptobenzaldehyde at the B3LYP/6-31+G* optimized geometry are in good agreement with those of previous experimental data. The results show that the inclusion of electron correlation at the B3LYP levels is more crucial in comparing the relative stability among the conformers of 2-mercaptobenzaldehede than among the conformers of salicylaldehede. The hydrogen-bonding energies are estimated by comparing the molecular energies between two different conformations either with a hydrogen bond or with no hydrogen bond of a given molecule. These energies for salicylaldehyde and 2-mercaptobenzaldehyde are computed to be about 9 and 2 kcal/mol at the B3LYP levels, respectively.

Interference of H-bonding and substituent effects in nitro- and hydroxy-substituted salicylaldehydes

“…Two of the four possible conformations of salicylaldehyde (see Scheme 1) and its derivatives were considered in the study. Conformation (I) presented in Scheme 1 was found to be the most stable in many studies, e.g., [11], whereas the open conformation, labelled (II) in Scheme 1, was necessary for the analysis presented in this study. Table 1 summarises all the data concerning the strength of intramolecular H-bonding, where the studied systems are presented in sequence from the strongest down to the weakest, taking into account the overall energy of the Hbond, E tot .…”

DFT RX3LYP and RPBEPBE studies on the structural, electronic, and vibrational properties of some amino-alcohol ligands

“…It has been suggested, however, that the B3LYP functional is inadequate for the description of weak interactions in chemical systems (and this is what we expected to be present in our ligands) because of the lack of electron-electron correlation [35][36][37]. The inclusion of electron correlation, as well as the use of flexible and extended basis sets augmented with diffuse functions, is important for accurately describing H-bonding and van der Waals interactions [38][39][40][41] since the choice of basis set influences not only the relative energetic stability of conformers, but also the number of local minima, and that is important in correctly analyzing the low energy barriers to internal rotation [42,43]. An extension to B3LYP, called X3LYP, addresses this issue to some extent.…”

Hydrogen bonding interaction between 1,4‐dioxane and water

“…The geometries of 1,4‐dioxane‐(water) n ( n = 1–3) complexes have been optimized using density functional theory with B3LYP 34–37 hybrid functional and 6‐311++G* basis set. It is well known that the inclusion of electron correlation as well as the use of basis function that includes both, diffuse and polarization functions is necessary for the accurate description of hydrogen bonding interactions 38–42. 6‐311++G* is one of the most popular basis set used in the study of medium and large size hydrogen bonded systems.…”