Open AccessObservation of water dangling OH bonds around dissolved nonpolar groups
Author(s) -
Pradeep N. Perera,
K. Rebecca Fega,
C. P. Lawrence,
Eric J. Sundstrom,
Jill Tomlinson-Phillips,
Dor BenAmotz
Publication year - 2009
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.0903675106
Subject(s) - solvation shell , neopentane , chemistry , dangling bond , benzene , hydrogen bond , hydrocarbon , raman spectroscopy , molecule , infrared spectroscopy , photochemistry , crystallography , analytical chemistry (journal) , organic chemistry , hydrogen , solvation , optics , physics
We report the experimental observation of water dangling OH bonds in the hydration shells around dissolved nonpolar (hydrocarbon) groups. The results are obtained by combining vibrational (Raman) spectroscopy and multivariate curve resolution (MCR), to reveal a high-frequency OH stretch peak arising from the hydration shell around nonpolar (hydrocarbon) solute groups. The frequency and width of the observed peak is similar to that of dangling OH bonds previously detected at macroscopic air–water and oil–water interfaces. The area of the observed peak is used to quantify the number of water dangling bonds around hydrocarbon chains of different length. Molecular dynamics simulation of the vibrational spectra of water molecules in the hydration shell around neopentane and benzene reveals high-frequency OH features that closely resemble the experimentally observed dangling OH vibrational bands around neopentyl alcohol and benzyl alcohol. The red-shift of ≈50 cm−1 induced by aromatic solutes is similar to that previously observed upon formation of a π-H bond (in low-temperature benzene–water clusters).