Vibrational signatures of carboxylic acid microhydration for the HyDRA project

02 June 2025, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

HyDRA aims at the systematic experimental characterisation of water vibrations in different microsolvation situations for the purpose of quantum chemistry benchmarking, where quantum chemistry involves suitable combinations of electronic structure and nuclear dynamics treatments. The current HyDRA database largely lacks acid microsolvation data. This is cured by the present contribution, which characterises neutral microhydrates of formic and acetic acid by supersonic jet FTIR and Raman spectroscopy. The centroid of the bound water OH stretching fundamental in the monohydrate of formic acid is located at 3535(4) cm-1. Literature monohydrate spectra of benzoic acid are confirmed. A surprisingly abundant metastable monohydrate of the acetic acid dimer is identified. The relationship between harmonic B3LYP carboxylic acid complexation shifts of water and the experimental OH stretching shifts is remarkably robust.

Keywords

water
hydrogen bond
microhydration
carboxylic acids
formic acid
acetic acid
benzoic acid
benchmark
Raman
IR
supersonic jet

Supplementary materials

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Supplementary information for the article
Description
used chemicals, experimental conditions, computational protocols, harmonic spectral predictions, energies, effect of planarisation, possible resonances, low frequency modes, raw spectra, database entries
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