Preferential interactions in the formamide/ tetrahydrofuran/dioxane system: a study by Raman spectroscopy

Abstract

Significant changes observed in the Raman spectra of formamide (FA)-tetrahydrofuran (THF)-dioxane (DX) mixtures have been interpreted in terms of preferential interactions. The Gutmann's donor (DN) and acceptor (AN) number values of these solvents give a good interpretation for the differences observed. In the ternary system, THF behaves as a stronger base than DX and the band at ∼442 cm −1 , recently assigned to the FA-DX adduct is only observed at the highest FA concentration. Quantitative analyses performed at the C O (FA) and C-O (THF) stretching regions show that the extent of the association for the [FA]n adduct is significantly larger than for the FA-THF adduct. Electrostatic parameters, such as dipole moment and dielectric constant, are also regarded as a better interpretation of these associations. The good correlation between DN and electrostatic parameters indicates that the basic strength increases in the order DX < THF < FA.

Hydrogen bonding in the pyrimidine/ formamide system: a concentration‐dependent Raman and DFT study

“…From this perspective, there will be fewer FA monomers to interact with PD molecules in FA‐rich mixtures, resulting in the formation of only a group of hydrogen‐bonded species, on the contrary to what has been observed in w‐rich mixtures. These interpretations find support in a few of our articles8, 10 and in an important work published by Grabowski et al ,14 where the intermolecular distances and binding energies of various hydrogen‐bonded complexes have been reported.…”

“…Because it is the simplest molecule exhibiting a peptide bond, formamide (FA) has been extensively studied by Alves and co‐workers4–10 as well as by other authors 11–13. Indeed, the participation of the CONHgroup in proteins is regarded as the key stage of enzyme catalysis, although the physical nature of such interactions still remains a controversial topic 14.…”

FT‐Raman, FTIR and density functional theory studies of a hydrogen‐bonded formamide:pyridine complex

“…[2] In those works, FA essentially acts as a Lewis acid where its N-H site causes wavenumber shifts of the characteristics bands of acetonitrile (ACN), [3] dimethylsulfoxide (DMSO), [4] tetrahydrofuran (THF), [5] and dioxane (DX). [6] In addition, interactions between FA molecules lead to wavenumber shifts of the C O stretching mode (basic site), [7,8] and both these shifts are in good agreement with its amphoteric character.…”

“…We can interpret it by recognizing the similarities in the physical chemistry properties of W and FA. [8] A harmonic vibrational wavenumber (ν 1 ) equal to 995 cm −1 has been determined by Schlücker et al [11] for the 1 : 1 PyW complex. Another Monte Carlo-based computational study of Py in W reported that 17% of Py showed no hydrogen bonding, 62% showed a single hydrogen bond, 20% two hydrogen bonds and 1% three hydrogen bonds.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part IV

“…Alves [246] published a study involving the preferential interactions in the formamide/tetrahydrofuran/dioxane ternary system using Raman spectroscopy. Donor-acceptor relations between these liquids was studied and it was found that a good correlation exists between donor and electrostatic parameters and that the basic strength increases in the order dioxane < tetrahydrofuran < formamide.…”