The Vapor Density and Some Other Properties of Formic Acid

Coolidge, Albert Sprague

doi:10.1021/ja01395a015

Cited by 114 publications

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“…These equilibrium constants fall in two broad categories -vapor density measurements 27 and spectroscopic monomer determinations. 26 The average value for K p p • from the vapor density results (including photoacoustic resonance, 28 but excluding the data which need major temperature extrapolation) is about 265(20) Pa, whereas spectroscopy yields significantly higher values above 350 Pa.…”

Section: Dissociation Energymentioning

confidence: 99%

Communication: The highest frequency hydrogen bond vibration and an experimental value for the dissociation energy of formic acid dimer

Kollipost

Larsen

Domanskaya

et al. 2012

The Journal of Chemical Physics

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The highest frequency hydrogen bond fundamental of formic acid dimer, ν24 (Bu), is experimentally located at 264 cm−1. FTIR spectra of this in-plane bending mode of (HCOOH)2 and band centers of its symmetric D isotopologues (isotopomers) recorded in a supersonic slit jet expansion are presented. Comparison to earlier studies at room temperature reveals the large influence of thermal excitation on the band maximum. Together with three Bu combination states involving hydrogen bond fundamentals and with recent progress for the Raman-active modes, this brings into reach an accurate statistical thermodynamics treatment of the dimerization process up to room temperature. We obtain D0 = 59.5(5) kJ/mol as the best experimental estimate for the dimer dissociation energy at 0 K. Further improvements have to wait for a more consistent determination of the room temperature equilibrium constant.

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Section: Dissociation Energymentioning

confidence: 99%

Communication: The highest frequency hydrogen bond vibration and an experimental value for the dissociation energy of formic acid dimer

Kollipost

Larsen

Domanskaya

et al. 2012

The Journal of Chemical Physics

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“…Molecular association of carboxylic acid molecules has been known for decades; it was proposed from the measurement of vapor density [1] for the first time. In the case of formic acid, the cyclic dimer (denoted as FAD hereafter) has been studied with electron diffraction techniques [2][3][4], and spectroscopic methods [5][6][7] quite extensively.…”

Section: Introductionmentioning

confidence: 99%

Infrared spectra of formic acid clusters in noble gas matrices

Ito

2015

Journal of Molecular Structure

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“…Under high backing pressure conditions, the liquid formic acid was kept at room temperature (25 C), and the vapor in equilibrium with the liquid was introduced into the interaction region through a 30 m diameter nozzle without constricting the flow by a needle valve. The heat generated by the thermionic cathode raised the temperature of the nozzle to 35 C. The vapor pressure at 25 C is 57.4 mbar [16], and the molar fraction of the dimers at this pressure and at 35 C can be calculated using the equilibrium constant determined by Coolidge [17] to be 71% . Under low backing pressure conditions, the pressure of the vapor was first reduced by a needle valve to 1 mbar (measured with a capacitance manometer) and then entered the interaction region through a 250 m diameter nozzle, also at 35 C. The vapor had enough time to reach the equilibrium dimer concentration at 1 mbar and 35 C, which corresponds to a dimer molar fraction of 11%.…”

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Electron Collisions with Formic Acid Monomer and Dimer

Allan

2007

Phys. Rev. Lett.

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Processes induced by the attachment of slow electrons to formic acid and its hydrogen-bonded dimer were studied. The elastic cross section and the cross section for the excitation of low quanta of discrete vibrations were found to be of a similar magnitude for both targets. A dramatic difference was found in the excitation of a vibrational quasicontinuum in the 1-2 eV range with the ejection of very slow electrons (E < 0:1 eV), which was about 20 more intense in the dimer. The association of two formic acid molecules to form a dimer thus dramatically increases the power to quasithermalize electrons arriving with energies in the 1-2 eV energy range. Rapid electron-driven intracluster proton transfer is invoked to explain the observation.The interest in electron-induced chemical processes has been recently renewed by the discovery that electrons at subionization [1] and even subexcitation energies [2] damage DNA. The biology-relevant discoveries inspired a series of gas phase studies of the various building blocks of DNA and other biomolecules [3,4]. The molecules in living tissue are, however, associated with neighboring molecules, often by means of hydrogen bridges, and it would thus be interesting to evaluate in what way this association affects the electron-induced processes.The dimer of formic acid is a suitable model system for such study, because it is one of the most stable neutral complexes with a complexation energy of 15 kcal mol ÿ1 (0.65 eV). The present work characterizes the collisions by means of measurement of the cross sections for vibrational excitation and for elastic scattering. The cross sections provide a detailed insight into electron-driven processes and the role played by resonances (temporary negative ions). This method was recently applied to the formic acid monomer [5]. The information obtained in this way is complementary to that obtained by studying the dissociative electron attachment, recently performed on clusters of formic acid and on condensed formic acid [6 -8], where a dramatic increase of cross sections with cluster size has been found.Particularly important for the interpretation of the present observation is the discovery, by means of anion photoelectron spectra and quantum chemical calculations, that hydrogen-bonded dimer anions of carboxylic acids (including amino acids and formic acid) and nucleic acid bases have a proton transferred from the acid to the base in their most stable structures and that this structure is reached by a barrier-free proton transfer (BFPT) [9,10]. The BFPT structure was also predicted theoretically for the formic acid dimer anion [11].Interesting phenomena were discovered in dissociative electron attachment to monomeric formic acid. The HCOO ÿ formate anion signal appeared at its energetic threshold at 1.25 eV [12]. The mechanism was clarified theoretically by Rescigno et al. [13]. High signal-to-noise ratio spectra revealed weak structures on the dissociative electron attachment band [12]. The absolute elastic cross sections as a function of sca...

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The Vapor Density and Some Other Properties of Formic Acid

Cited by 114 publications

References 0 publications

Communication: The highest frequency hydrogen bond vibration and an experimental value for the dissociation energy of formic acid dimer

Communication: The highest frequency hydrogen bond vibration and an experimental value for the dissociation energy of formic acid dimer

Infrared spectra of formic acid clusters in noble gas matrices

Electron Collisions with Formic Acid Monomer and Dimer

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