FTIR investigation of O···H···O hydrogen bonds with large proton polarizability in sulfonic acid–N-oxide systems in the middle and far-IR

Langner, Roland; Zuńdel, Georg

doi:10.1039/a801000e

Cited by 24 publications

(25 citation statements)

References 16 publications

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“…Proton continua have been also clearly observed in infrared spectra of liquid MSA and sulfuric acid. 38 > 41 > 42 This broad band for surface MSA (99+%, pK a of-1.9, 42 ) that begins before 2800 cm" 1 (estimated peak fit at 2500 cm" 1 ) and extends and decreases uniformly beyond 3800 cm" 1 indicates that proton transfer is occurring at the surface of MSA solutions.…”

Section: Vsf Of the Vapor/water Interfacementioning

confidence: 99%

Surface Structural Studies of Methanesulfonic Acid at Air /Aqueous Solution Interfaces Using Vibrational Sum Frequency Spectroscopy

2000

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Atmospheric gas phase species such as methanesulfonic acid (MSA) are adsorbed and accommodated into atmospheric aqueous-phase aerosols, and in some cases MSA is thought to be produced via aerosol surface chemistry. The studies described herein probe the surface molecular structure of MSA at aqueous solution surfaces using surface vibrational sum frequency spectroscopy (VSFS). In the studies presented here, it is shown that MSA partitions to the surface and that the surface MSA has a preferred orientation in which the methyl group points away from the liquid surface. The surrounding surface water structure is significantly affected by the adsorption of MSA. Small amounts of MSA at the surface of water cause the water molecule vibrational stretching modes to shift to lower energies. This shift is indicative of stronger coupling between the water molecules caused by the presence of MSA. Additional VSF studies show that MSA is effectively displaced by sulfuric acid at an aqueous surface. The structural details presented here may have implications for understanding atmospheric aerosol growth properties.

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Section: Vsf Of the Vapor/water Interfacementioning

confidence: 99%

Surface Structural Studies of Methanesulfonic Acid at Air /Aqueous Solution Interfaces Using Vibrational Sum Frequency Spectroscopy

2000

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“…In ref. 8 we have shown that single-minimum proton potentials are present in the SO···H + ···ON hydrogen bonds of these systems. In the case of small DpK a values a relatively narrow singleminimum is present at the donor.…”

Section: The Methanesulfonic Acid + N-oxide Family Of Systemsmentioning

confidence: 76%

“…The d HB values scatter strongly,and therefore, it seems that no precise information can be obtained. An analysis of the data shows, however, that a systematic course is found if one considers only the systems with N-bases having a relatively low and comparable shielding screening of the nitrogen atoms (systems 1,4,7,8,[11][12][13]16), indicating that the chemical shift of the proton is also influenced by sterical effects. The points of these systems (black squares) are on straight lines with a cross section at DpK a = 6.5 ± 0.5.…”

Section: The Dimethylphoshinic Acid + N-base Family Of Systemsmentioning

confidence: 99%

“…The double-minimum family (6) are the dimethylphosphinic acid (DMP, pK a = 3.8) + N-base systems with POH···N W PO -···H + N hydrogen bonds, and the broad flat single-minimum proton potential systems are the methanesulfonic acid (MSA, pK a = -1.92) + N-oxide systems with SO···H + ···ON hydrogen bonds (7,8). In the following, we compare the shape of the proton potential (double-minimum or broad flat single-minimum) with the position of the proton transfer equilibrium (50% proton transfer, i.e., symmetrical distribution of the proton in the hydrogen bonds).…”

Section: Introductionmentioning

confidence: 99%

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¹H NMR studies of proton transfer equilibria in hydrogen bonds the role of the entropy

Langner¹,

Zuńdel²

2001

Can. J. Chem.

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The influence of the entropy on the proton transfer equilibria AH···B W A -···H + B in the dimethylphosphinic acid (DMP)-N-base and in the methanesulfonic acid (MSA)-N-oxide hydrogen bonds is studied by 1 H NMR spectroscopy as a function of the DpK a , i.e., the pK a of the base minus the pK a of the acid. It is shown that with increasing DpK a the proton transfers to the N-oxide acceptor. In the DMP + N-base family of systems, first the double-minimum proton potentials (DH = 0) occurs and only with further increasing DpK a do the POH···N W PO -···H + N equilibria become symmetrical (DG = 0). DG and DH are connected by the Gibbs-Helmholtz equation, DG = DH -TDS. Hence, the reason of this effect is the large negative interaction entropy term (DS I ) arising from the large order around the polar structure, which shifts the equilibria strongly to the left-hand side. With the MSA-N-oxide hydrogen bonds a singleminimum proton potential was found. The minimum shifts with increasing DpK a from the donor to the acceptor of the O···H + ···N hydrogen bonds. It is shown that with increasing DpK a the proton potential becomes on average symmetrical, whereas the proton is still largely on the left-hand side. This result is also explained by the large negative interaction entropy due to the order of the environment if the proton is at the acceptor B.Résumé : Utilisant la spectroscopie RMN du 1 H en fonction du DpK a , c'est-à-dire du pK a de la base moins le pK a de l'acide, on a étudié l'influence de l'entropie sur l'équilibre de transfert de proton AH···B W A -···H + B dans les liaisons hydrogènes entre l'acide diméthylphosphinique (DMP) et le N d'une base et entre l'acide méthanesulfonique (MSA) et un azote, sous la forme d'oxyde d'azote. On a montré qu'une augmentation du DpK a conduit à un transfert de proton vers l'oxyde d'azote qui agit comme accepteur. Dans la famille de systèmes DMP + N-base, on observe au début un double-minimum des potentiels de protons (DH = 0); l'équilibre POH···N W PO -···H + N ne devient symétrique (DG = 0) qu'en augmentant le DpK a encore plus. Les DG et DH sont liés par l'équation de Gibbs-Helmholtz, DG = DH -TDS. On peut en conclure que cet effet est causé par un terme d'entropie d'interaction négative, DS I , qui est très élevé et qui découle d'un ordre très important autour de la structure polaire qui déplace fortement l'équilibre vers la gauche. Avec les liaisons hydrogènes MSA -oxyde d'azote on n'a observé qu'un seul minimum. Les minima se déplacent avec une augmentation des DpK a du donneur vers l'accepteur des liaisons hydrogènes O···H + ···N. On a montré qu'avec une augmentation du DpK a , le potentiel des protons prend déjà une forme moyenne qui est symétrique même si le proton est encore principalement vers la gauche. On peut aussi expliquer ce résultat par la présence d'une entropie d'interaction fortement négative qui résulte de l'environnement si le proton se trouve au niveau de l'accepteur B.

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“…This broad band for surface MSA (99+%, pK a of-1.9, 42 ) that begins before 2800 cm" 1 (estimated peak fit at 2500 cm" 1 ) and extends and decreases uniformly beyond 3800 cm" In Figures 4a and 4b, additional significant spectral features are observed that provide information about the structure of water at the surface of these MSA solutions. The destructive interference between the VSF response of the CH 3 -SS and the CH 3 -AS that was previously discussed, is clearly evident in the VSF spectra and remains relatively unchanged with changing MSA concentration.…”

mentioning

confidence: 83%

Surface Structural Studies of Methane Sulfonic Acid at Air/Aqueous Solution Interfaces using Vibrational Sum Frequency Spectroscopy

Allen¹,

Raymond²,

Richmond³

2000

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FTIR investigation of O···H···O hydrogen bonds with large proton polarizability in sulfonic acid–N-oxide systems in the middle and far-IR

Cited by 24 publications

References 16 publications

Surface Structural Studies of Methanesulfonic Acid at Air /Aqueous Solution Interfaces Using Vibrational Sum Frequency Spectroscopy

Surface Structural Studies of Methanesulfonic Acid at Air /Aqueous Solution Interfaces Using Vibrational Sum Frequency Spectroscopy

¹H NMR studies of proton transfer equilibria in hydrogen bonds the role of the entropy

Surface Structural Studies of Methane Sulfonic Acid at Air/Aqueous Solution Interfaces using Vibrational Sum Frequency Spectroscopy

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FTIR investigation of O···H···O hydrogen bonds with large proton polarizability in sulfonic acid–N-oxide systems in the middle and far-IR

Cited by 24 publications

References 16 publications

Surface Structural Studies of Methanesulfonic Acid at Air /Aqueous Solution Interfaces Using Vibrational Sum Frequency Spectroscopy

Surface Structural Studies of Methanesulfonic Acid at Air /Aqueous Solution Interfaces Using Vibrational Sum Frequency Spectroscopy

1H NMR studies of proton transfer equilibria in hydrogen bonds  the role of the entropy

Surface Structural Studies of Methane Sulfonic Acid at Air/Aqueous Solution Interfaces using Vibrational Sum Frequency Spectroscopy

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¹H NMR studies of proton transfer equilibria in hydrogen bonds the role of the entropy