Low-frequency Raman spectra and molecular association in liquid formic and acetic acids

Waldstein, Peter; Blatz, L. A.

doi:10.1021/j100866a047

Cited by 70 publications

(36 citation statements)

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“…4,5 Liquid formic acid is instead considered to exist in the form of a H-bonded network, involving a variety of chain like structures, different from both that of the gas and of crystal. [6][7][8][9][10][11] Moreover, a cis molecular structure, different from the trans structure existing in normal conditions (the trans/cis nomenclature refers to the position of the hydrogen atoms), has been observed in crystalline formic acid under high-pressure. 12 Liquid formic acid has been investigated by a number of experimental techniques, including Raman 8,13,14 and NMR 15, 16 spectroscopy, X-ray 6,9,10,17,18 and neutron 6,10,19 diffraction, and dielectric measurements.…”

Section: Introductionmentioning

confidence: 99%

Structure of Liquid Formic Acid Investigated by First Principle and Classical Molecular Dynamics Simulations

2005

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The structure of liquid formic acid has been investigated by Car-Parrinello and classical molecular dynamics simulations, focusing on the characterization of the H-bond network and on the mutual arrangement of pairs of bonded molecules. In agreement with previous computational studies, two levels of H-bonded structures have been found. Small clusters, characterized by O-H...O bonds, are held together by weak C-H...O bonds to form large branched structures. From the ab initio simulation we infer the importance of cyclic H-bond dimer configurations, typical of the gas phase. Most of these dimer structures are however found to be embedded into H-bonded chains. When only O-H...O bonds are taken into account, linear H-bond chains are detected as basic structures of the liquid. More branched structures occur when C-H...O bonds are also considered. Regarding the arrangement of molecular pairs, we observed that O-H...O bonds favor the occurrence of configurations with parallel molecular planes, whereas no preferential orientation is observed for molecules forming C-H...O bonds.

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Section: Introductionmentioning

confidence: 99%

Structure of Liquid Formic Acid Investigated by First Principle and Classical Molecular Dynamics Simulations

2005

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“…Except under extremely high pressure, interactions involving the methyl groups are rather weak under most conditions [1] , while the carbonyl and hydroxyl are both active and form hydrogen bonds (H-bond) with each other. This feature leads the HOAc to form a cyclic dimer in most phases, such as gas [2,3] , some nonpolar solvents [4][5][6] , and pure liquid [7] . As in aqueous solutions, an equilibrium between monomeric HOAc and its cyclic dimer was found and characterized by a dimerization constant K D [8][9][10][11][12] .…”

Section: Introductionmentioning

confidence: 99%

Hydrogen bonding of single acetic acid with water molecules in dilute aqueous solutions

Sun

Zhang

2009

Sci. China Ser. B-Chem.

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In separation processes, hydrogen bonding has a very significant effect on the efficiency of isolation of acetic acid (HOAc) from HOAc/H 2 O mixtures. This intermolecular interaction on aggregates composed of a single HOAc molecule and varying numbers of H 2 O molecules has been examined by using ab initio molecular dynamics simulations (AIMD) and quantum chemical calculations (QCC). Thermodynamic data in aqueous solution were obtained through the self-consistent reaction field calculations and the polarizable continuum model. The aggregation free energy of the aggregates in gas phase as well as in aqueous system shows that the 6-membered ring is the most favorable structure in both states. The relative stability of the ring structures inferred from the thermodynamic properties of the QCC is consistent with the ring distributions of the AIMD simulation. The study shows that in dilute aqueous solution of HOAc the more favorable molecular interaction is the hydrogen bonding between HOAc and H 2 O molecules, resulting in the separation of acetic acid from the HOAc/H 2 O mixtures with more difficulty than usual. acetic acid, hydrogen bond, ab initio, molecular dynamics, free energy

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“…[8][9][10][11][12][13][14] Several infrared and Raman investigations show the existence of cyclic dimers and the chainlike polymer structure in the liquid state. 12,13 Nevertheless, based on the results of Raman spectral study, Bartholomew and Irish 14 concluded that liquid formic acid should be viewed as a col-lection of monomeric units which interact through hydrogen bonding, thereby imposing local, short-term order in the liquid. Other workers 8 also suggested that the role of the cyclic dimers, characteristic of the gas phase with two O-H---O hydrogen bonds, is minor ͑7% of the molecules͒ in the liquid formic acid.…”

Section: Introductionmentioning

confidence: 99%

Pressure-dependent studies on hydration of the C–H group in formic acid

Chang

Jiang

Chao

et al. 2001

The Journal of Chemical Physics

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The infrared spectroscopic profiles of HCOOD/D 2 O mixtures were measured as a function of pressure and concentration. The C-H bond of HCOOD shortens as the pressure is elevated, while the increase in C-H bond length upon diluting HCOOD with D 2 O was observed. Based on the experimental results, the shift in frequency of C-H stretching band is concluded to relate to the mechanism of the hydration of the C-H group and the water structure in the vicinity of the C-H group. The pressure-dependent results can be attributed to the strengthening of C-H---O electrostatic/dispersion interaction upon increasing pressure. The observations are in accord with ab initio calculation forecasting a blueshift of the C-H stretching mode via C-H---O interaction in HCOOD-water/͑HCOOD͒ 2 -͑D 2 O͒ complexes relative to the noninteracting monomer/dimer. Hydrogen-bonding nonadditivity and the size of water clusters are suggested to be responsible to cause the redshift in C-H stretching mode upon dilution HCOOD with D 2 O.

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Low-frequency Raman spectra and molecular association in liquid formic and acetic acids

Cited by 70 publications

References 1 publication

Structure of Liquid Formic Acid Investigated by First Principle and Classical Molecular Dynamics Simulations

Structure of Liquid Formic Acid Investigated by First Principle and Classical Molecular Dynamics Simulations

Hydrogen bonding of single acetic acid with water molecules in dilute aqueous solutions

Pressure-dependent studies on hydration of the C–H group in formic acid

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