Molecular sinkers: x-ray photoemission and atomistic simulations of benzoic acid and benzoate at the aqueous solution/vapor interface

Niklas Ottosson, Anastasia O. Romanova, Johan Soderstrom, Olle Bjorneholm, Gunnar Ohrwall, Maxim V. Fedorov

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

In this work, we provide a detailed microscopic picture of the behavior of benzoic acid at the aqueous solution/vapor interface in its neutral as well as in its dissociated form (benzoate). This is achieved through a combination of highly surface-sensitive X-ray photoelectron spectroscopy experiments and fully atomistic molecular simulations. We show that significant changes occur in the interface behavior of the neutral acid upon release of the proton. The benzoic acid molecules are found to be strongly adsorbed at the interface layer with the planes of the aromatic rings oriented almost parallel to the water surface. In contrast, in the benzoate form, the carboxylate group shows a sinker-like behavior while the aromatic ring acts as a buoy, oriented nearly perpendicular to the surface. Furthermore, a significant fraction of the molecular ions move from the interface layer into the bulk of the solution. We rationalize these findings in terms of the very different hydration properties of the carboxylic group in the two charge states. The molecule has an amphiphilic nature, and the deprotonation thus changes the hydrophobic/hydrophilic balance between the nonpolar aromatic and the polar carboxylic parts of the molecule. That, consequently, leads to a pronounced reorientation and depletion of the molecules at the interface.

LanguageEnglish
Pages13017-13023
Number of pages7
JournalJournal of Physical Chemistry B
Volume116
Issue number43
DOIs
Publication statusPublished - 1 Nov 2012

Fingerprint

Benzoic Acid
Benzoic acid
Benzoates
benzoic acid
Photoemission
photoelectric emission
Vapors
vapors
aqueous solutions
X rays
Molecules
x rays
simulation
molecules
Deprotonation
Hydration
rings
Protons
surface water
molecular ions

Keywords

  • molecular sinkers
  • x-ray photoemission
  • atomistic simulations
  • benzoate
  • aqueous solution
  • vapor interface

Cite this

Ottosson, Niklas ; Romanova, Anastasia O. ; Soderstrom, Johan ; Bjorneholm, Olle ; Ohrwall, Gunnar ; Fedorov, Maxim V. / Molecular sinkers : x-ray photoemission and atomistic simulations of benzoic acid and benzoate at the aqueous solution/vapor interface. In: Journal of Physical Chemistry B. 2012 ; Vol. 116, No. 43. pp. 13017-13023.
@article{4f5b2f237d1949aaa152d9459d3ed2c4,
title = "Molecular sinkers: x-ray photoemission and atomistic simulations of benzoic acid and benzoate at the aqueous solution/vapor interface",
abstract = "In this work, we provide a detailed microscopic picture of the behavior of benzoic acid at the aqueous solution/vapor interface in its neutral as well as in its dissociated form (benzoate). This is achieved through a combination of highly surface-sensitive X-ray photoelectron spectroscopy experiments and fully atomistic molecular simulations. We show that significant changes occur in the interface behavior of the neutral acid upon release of the proton. The benzoic acid molecules are found to be strongly adsorbed at the interface layer with the planes of the aromatic rings oriented almost parallel to the water surface. In contrast, in the benzoate form, the carboxylate group shows a sinker-like behavior while the aromatic ring acts as a buoy, oriented nearly perpendicular to the surface. Furthermore, a significant fraction of the molecular ions move from the interface layer into the bulk of the solution. We rationalize these findings in terms of the very different hydration properties of the carboxylic group in the two charge states. The molecule has an amphiphilic nature, and the deprotonation thus changes the hydrophobic/hydrophilic balance between the nonpolar aromatic and the polar carboxylic parts of the molecule. That, consequently, leads to a pronounced reorientation and depletion of the molecules at the interface.",
keywords = "molecular sinkers, x-ray photoemission, atomistic simulations, benzoate, aqueous solution, vapor interface",
author = "Niklas Ottosson and Romanova, {Anastasia O.} and Johan Soderstrom and Olle Bjorneholm and Gunnar Ohrwall and Fedorov, {Maxim V.}",
year = "2012",
month = "11",
day = "1",
doi = "10.1021/jp300956j",
language = "English",
volume = "116",
pages = "13017--13023",
journal = "Journal of Physical Chemistry B",
issn = "1520-6106",
publisher = "American Chemical Society",
number = "43",

}

Molecular sinkers : x-ray photoemission and atomistic simulations of benzoic acid and benzoate at the aqueous solution/vapor interface. / Ottosson, Niklas; Romanova, Anastasia O.; Soderstrom, Johan; Bjorneholm, Olle; Ohrwall, Gunnar; Fedorov, Maxim V.

In: Journal of Physical Chemistry B, Vol. 116, No. 43, 01.11.2012, p. 13017-13023.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Molecular sinkers

T2 - Journal of Physical Chemistry B

AU - Ottosson, Niklas

AU - Romanova, Anastasia O.

AU - Soderstrom, Johan

AU - Bjorneholm, Olle

AU - Ohrwall, Gunnar

AU - Fedorov, Maxim V.

PY - 2012/11/1

Y1 - 2012/11/1

N2 - In this work, we provide a detailed microscopic picture of the behavior of benzoic acid at the aqueous solution/vapor interface in its neutral as well as in its dissociated form (benzoate). This is achieved through a combination of highly surface-sensitive X-ray photoelectron spectroscopy experiments and fully atomistic molecular simulations. We show that significant changes occur in the interface behavior of the neutral acid upon release of the proton. The benzoic acid molecules are found to be strongly adsorbed at the interface layer with the planes of the aromatic rings oriented almost parallel to the water surface. In contrast, in the benzoate form, the carboxylate group shows a sinker-like behavior while the aromatic ring acts as a buoy, oriented nearly perpendicular to the surface. Furthermore, a significant fraction of the molecular ions move from the interface layer into the bulk of the solution. We rationalize these findings in terms of the very different hydration properties of the carboxylic group in the two charge states. The molecule has an amphiphilic nature, and the deprotonation thus changes the hydrophobic/hydrophilic balance between the nonpolar aromatic and the polar carboxylic parts of the molecule. That, consequently, leads to a pronounced reorientation and depletion of the molecules at the interface.

AB - In this work, we provide a detailed microscopic picture of the behavior of benzoic acid at the aqueous solution/vapor interface in its neutral as well as in its dissociated form (benzoate). This is achieved through a combination of highly surface-sensitive X-ray photoelectron spectroscopy experiments and fully atomistic molecular simulations. We show that significant changes occur in the interface behavior of the neutral acid upon release of the proton. The benzoic acid molecules are found to be strongly adsorbed at the interface layer with the planes of the aromatic rings oriented almost parallel to the water surface. In contrast, in the benzoate form, the carboxylate group shows a sinker-like behavior while the aromatic ring acts as a buoy, oriented nearly perpendicular to the surface. Furthermore, a significant fraction of the molecular ions move from the interface layer into the bulk of the solution. We rationalize these findings in terms of the very different hydration properties of the carboxylic group in the two charge states. The molecule has an amphiphilic nature, and the deprotonation thus changes the hydrophobic/hydrophilic balance between the nonpolar aromatic and the polar carboxylic parts of the molecule. That, consequently, leads to a pronounced reorientation and depletion of the molecules at the interface.

KW - molecular sinkers

KW - x-ray photoemission

KW - atomistic simulations

KW - benzoate

KW - aqueous solution

KW - vapor interface

UR - http://www.scopus.com/inward/record.url?scp=84868249974&partnerID=8YFLogxK

U2 - 10.1021/jp300956j

DO - 10.1021/jp300956j

M3 - Article

VL - 116

SP - 13017

EP - 13023

JO - Journal of Physical Chemistry B

JF - Journal of Physical Chemistry B

SN - 1520-6106

IS - 43

ER -