Stability of Mono-Hydrated Ether Complexes in the Gas-Phase at Room Temperature

Hydrogen bonding between water and volatile organic compounds (VOCs) plays a central role in atmospheric clustering and nucleation processes. We investigate the hydrogen-bonded complexes formed between water (H₂O) and three ethers: diethyl ether (DEE), tetrahydrofuran (THF), and ethyl vinyl ether (EVE) at room temperature in the gas phase using infrared spectroscopy and compare with previously reported spectra of H₂O·DME (dimethyl ether). Infrared spectra recorded at room temperature reveal distinct bound and free OH-stretching fundamentals of the H₂O unit in the monohydrated complexes. The observed red shifts of the bound OH-stretch establish a clear trend in hydrogen bond strength: H₂O·DEE ≈ H₂O·THF > H₂O·DME > H₂O·EVE, which is rationalized in terms of inductive effects, enhanced lone-pair availability, and π-delocalization effects that modulate the hydrogen-bond acceptor ability of the ether oxygen. We use reduced-dimensional anharmonic vibrational calculation to assign the measured spectra and determine the oscillator strengths of the OH-stretching transitions. In conjunction with measured band intensities, equilibrium constants (Gibbs energies) of complex formation are determined. These results provide room temperature thermodynamic characterization of H₂O·ether complexes and establish a robust combined experimental-theoretical framework for quantifying weak hydrogen bonds relevant to atmospheric chemistry.