Étude des mélanges eau–HF par spectroscopie infrarouge à transformée de Fourier

Khorami, J.; Beaudoin, Réjean; Ménard, Hugues

doi:10.1139/v87-138

Cited by 11 publications

(22 citation statements)

References 3 publications

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“…It is also noted that no narrow IR absorption bands appear near this frequency for dilute aqueous HF solutions. 39,40 Furthermore, no additional structure was seen to indicate a similar interaction between acetic acid or HCl and surface NH x species ͑see below͒.…”

Section: Resultsmentioning

confidence: 99%

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Wet-Chemical Treatment of Si[sub 3]N[sub 4] Surfaces Studied Using Infrared Attenuated Total Reflection Spectroscopy

Bermudez

2005

J. Electrochem. Soc.

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Infrared attenuated total reflection spectroscopy has been used to observe the surface chemistry of Si 3 N 4 films ͑grown on Si by low-pressure chemical vapor deposition͒ under steady-state conditions during exposure to dilute aqueous HF solutions. Surfaces etched in HF do not exhibit rapid growth of an SiO 2 layer when subsequently exposed to either humid room air at room temperature or to liquid H 2 O. However, some evidence is found for the formation of an ultrathin oxide-like layer when the etched surface is rinsed in deionized H 2 O. Removal of this layer in HF results in no detectable signal in the Si-H stretching region, unlike the case for Si subjected to a similar oxide-removal treatment. The presence of SiOH groups has been detected by observing their removal by reaction with aqueous acetic acid or HCl solutions, which suggests that SiH x groups are rapidly hydrolyzed. An attempt was made to detect surface NH x groups by protonation in aqueous acid to form NH xϩ1 ϩ , which should be more readily observable in the infrared spectrum. However, the surface coverage of NH x , if any, is too small to be detected by this means.

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Section: Resultsmentioning

confidence: 99%

“…No evidence is seen for the formation of SiH x groups on the Si 3 N 4 surface following exposure to HF. The weak broad band at ϳ1850 cm Ϫ1 is a characteristic 39,40 of aqueous HF solutions.…”

Section: Resultsmentioning

confidence: 99%

Wet-Chemical Treatment of Si[sub 3]N[sub 4] Surfaces Studied Using Infrared Attenuated Total Reflection Spectroscopy

Bermudez

2005

J. Electrochem. Soc.

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“…[12,13] But, as for bifluoride, infrared and Raman experiments do not support these results. [10,11] Some more recent spectroscopic investigations even support the description of the liquid as hydronium fluoride. [14] It appears crucial then to determine which ions are indeed present in the liquid at 50 %-50 % concentration.…”

Section: Introductionmentioning

confidence: 93%

“…On the other hand, infrared and Raman experiments provide no evidence of the existence of bifluoride ions below 38 [10] or even 50 %. [11] The other polyfluoride ions F(HF) n À (n = 2) either have been revealed by potentiometry and electrical conductivity experiments around 10 % molar or are supposed to be formed at higher concentrations for n = 3, 4. [12,13] But, as for bifluoride, infrared and Raman experiments do not support these results.…”

Section: Introductionmentioning

confidence: 99%

Ab Initio Molecular Dynamics Simulation of a Water–Hydrogen Fluoride Equimolar Mixture

Simon¹,

Klein

2005

ChemPhysChem

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Hydrogen fluoride and water can be mixed in any proportion. The resulting solutions have unique acidic properties. In particular, hydrogen fluoride undergoes a weak-to-strong acidity transition with increasing concentration of HF To supplement the knowledge already obtained on dilute or moderately concentrated solutions and gas-phase aggregates, an equimolar mixture is studied here by Car-Parrinello molecular dynamics. The natures of the ions and of the complexes formed in the equimolar liquid were determined. Specifically, H3O+, H5O2+, FH-OH2, and HF2- were spontaneously obtained while only hydronium and fluoride ions pre-exist in the equimolar crystal. The behaviour of the proton in the equimolar liquid was compared with mixtures of other proportions simulated previously in an attempt to relate proton dynamics to acidity. In the same way, the behaviour of HF2- was also examined. In this case, proton localization and transfer appeared to be driven by the fluctuating environment of the solvated ion.

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“…Several theoretical investigations [19][20][21][22][23][24][25][26][27][28][29][30] have attempted to shed light on this controversy by providing a molecular-level description of the acid ionization/dissociation mechanism while seeking an interpretation of the thermodynamics and spectroscopic properties of liquid [31][32][33] and crystalline 34,35 hydrogen fluoride, and its aqueous liquid [36][37][38][39][40][41] and amorphous solid [42][43][44] solutions. Probing and modeling the structure, the stability and the ultrafast interconversion dynamics of the various intermediates along the complex collective solvent reaction coordinate of R1 remains a considerable contemporary challenge.…”

Section: Introductionmentioning

confidence: 99%

Trapping proton transfer intermediates in the disordered hydrogen-bonded network of cryogenic hydrofluoric acid solutions

Ayotte

Plessis

Marchand

2008

Phys. Chem. Chem. Phys.

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A molecular-level description of the structural and dynamical aspects that are responsible for the weak acid behaviour of dilute hydrofluoric acid solutions and their unusual increased acidity at near equimolar concentrations continues to elude us. We address this problem by reporting reflection-absorption infrared spectra (RAIRS) of cryogenic HF-H(2)O binary mixtures at various compositions prepared as nanoscopic films using molecular beam techniques. Optical constants for these cryogenic solutions [n(omega) and k(omega)] are obtained by iteratively solving Fresnel equations for stratified media. Modeling of the experimental RAIRS spectra allow for a quantitative interpretation of the complex interplay between multiple reflections, optical interference and absorption effects. The evolution of the strong absorption features in the intermediate 1000-3000 cm(-1) range with increasing HF concentration reveals the presence of various ionic dissociation intermediates that are trapped in the disordered H-bonded network of cryogenic hydrofluoric acid solutions. Our findings are discussed in light of the conventional interpretation of why hydrofluoric acid is a weak acid revealing molecular-level details of the mechanism for HF ionization that may be relevant to analogous elementary processes involved in the ionization of weak acids in aqueous solutions.

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Étude des mélanges eau–HF par spectroscopie infrarouge à transformée de Fourier

Cited by 11 publications

References 3 publications

Wet-Chemical Treatment of Si[sub 3]N[sub 4] Surfaces Studied Using Infrared Attenuated Total Reflection Spectroscopy

Wet-Chemical Treatment of Si[sub 3]N[sub 4] Surfaces Studied Using Infrared Attenuated Total Reflection Spectroscopy

Ab Initio Molecular Dynamics Simulation of a Water–Hydrogen Fluoride Equimolar Mixture

Trapping proton transfer intermediates in the disordered hydrogen-bonded network of cryogenic hydrofluoric acid solutions

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