Bulk Response of Carboxylic Acid Solutions Observed with Surface Sum-Frequency Generation Spectroscopy.

ABSTRACT: We study the molecular properties of aqueous acetic acid and formic acid solutions with heterodyne-detected vibrational sum-frequency generation spectroscopy (HD-VSFG). For acid concentrations up to ∼5 M, we observe a strong increase of the responses of the acid hydroxyl and carbonyl stretch vibrations with increasing acid concentration due to an increase of the surface coverage by the acid molecules. At acid concentrations >5 M we observe first a saturation of these responses and then a decrease. For pure carboxylic acids we even observe a change of sign of the Im[χ⁽²⁾] response of the carbonyl vibration. The decrease of the response of the hydroxyl vibration and the decrease and sign change of the response of the carbonyl vibration indicate the formation of cyclic dimers, whic

SUBMITTER: Moll CJ 

PROVIDER: S-EPMC8762667 | biostudies-literature | 2022 Jan

REPOSITORIES: biostudies-literature