Exploring the Solvation of Acetic Acid in Water Using Liquid Jet X-ray Photoelectron Spectroscopy and Core Level Electron Binding Energy Calculations

Abstract

Liquid jet X-ray photoelectron spectroscopy was used to investigate changes in the local electronic structure of acetic acid in the bulk of aqueous solutions induced by solvation effects. These effects manifest themselves as shifts in the difference in the carbon 1s binding energy (ΔBE) between the methyl and carboxyl carbons of acetic acid. Furthermore, molecular dynamics simulations, coupled with correlated electronic structure calculations of the first solvation sphere, provide insight into the number of water molecules directly interacting with the carboxyl group that are required to match the ΔBE from the photoelectron spectroscopy experiments. This comparison shows that a single water molecule in the first solvation shell describes the photoelectron ΔBE of acetic acid while at least 20 water molecules are required for the conjugate base, acetate, in aqueous solutions.

Molecular orientation of small carboxylates at the water–air interface

“…[1][2][3][4][5][6][7][8] The chemical and physical properties of the carboxylate anion differ strongly from those of the conjugate carboxylic acid. [9][10][11] Particularly, carboxylates form strong ionic bonds with different metal cations, giving rise to metal carboxylates and more elaborate structures such as carboxylate based metal organic frameworks. [12][13][14][15][16] Longchain carboxylates are also frequently utilized as surfactants to solubilize hydrocarbons in fuel extraction.…”

Photoelectron circular dichroism in angle-resolved photoemission from liquid fenchone

“…No discernible features can be attributed to gas-phase contributions to the spectrum. This is unusual compared to photoelectron spectra of other substances probed in liquid microjet experiments, most notably water, 52 but also, e.g., methanol, 53 acetic-acid solutions, 54 and liquid ammonia. 55 In principle, two explanations are conceivable: The gas-phase contributions are too low in intensity to become apparent, or they overlap-in this case-with the features stemming from the liquid phase.…”

Superficial Tale of Two Functional Groups: On the Surface Propensity of Aqueous Carboxylic Acids, Alkyl Amines, and Amino Acids

“…Surface enrichment varies depending on the species and conditions, and concentrations 1 to 2 orders of magnitude higher have been reported for relatively small organic compounds. , The carboxylic and amine groups are two common titratable functional groups in organics. Molecules containing carboxylic and amine groups, e.g., carboxylic acids, alkyl amines, and amino acids, − ,,− can thus be expected to have surface propensities depending on both the nature of any hydrophobic groups and the pH-dependent protonation state of the functional group, which is the topic of this Account. Here we will review some results, obtained with liquid-jet XPS and theoretical simulations, of the surface behavior of molecules containing carboxylic and amine groups in both individual carboxylic acids and alkyl amines species, together in a mixed solution and combined into amino acids.…”