Hydrophobic effects in the water network structure of aqueous solutions of a semiclathrate molecule

Abstract

In-phase collective small amplitude proton motions are observed in the OH stretching Raman spectrum of the semiclathrate crystalline hydrate of tetra-n-butyl ammonium hydroxide, its melt and aqueous solutions. These are quantified and used in dilute solutions as a probe of the network structure of water surrounding the molecule. Clear evidence of structural enhancement of the network is obtained in dilute solutions as well as the destruction of the network by hydrophobic interactions as the concentration is increased. Evidence for change of molecular conformation, suggesting intramolecular hydrophobic interactions, is obtained from the CH stretching spectra.

Raman spectroscopic study on the structure of water in aqueous solution of zwitterionic surfactants

“…The simple electrolyte-induced decrease in scattering intensity around 3250 cm −1 corresponding to the collective band was also observed by two-dimensional correlation Raman spectroscopy [46]. In contrast, those of hydrophobic substances such as t-butanol [37] (p X = 0.04) and tetra-n-butyl ammonium hydroxide [38] (p X = 0.013) were higher than that of pure water, due to an enhancement of the H-bond between water molecules in hydrophobic hydration shells around the hydrocarbon moiety [47]. These results show that the vibrational band attributed to the O-H oscillators of the water cluster can be distinguished from that of the water hydrated to solutes by using polarized Raman spectroscopy and that this method has the ability to detect changes in the H-bonded network structure of water even in dilute on semidilute aqueous solutions (p X = 0.01-0.05, 0.55-2.8 mol/l)).…”

“…However, as exemplified in Fig. 1b, the component of the O-H stretching band of water centered at 3250 cm −1 was highly polarized and diminished in the spectra at a perpendicular position [33][34][35][36][37][38][39]. The polarized O-H stretching band of water, which is called the collective band, is ascribed to the H 2 O molecule executing ν 1 vibrations all in phase with each other, but the vibrational amplitude varying from molecule to molecule in water clusters that are strongly H-bonded [40][41][42].…”

Raman spectroscopic study on the structure of water in aqueous solution of -amino acids

“…The simple electrolyte-induced decrease in scattering intensity around 3250 cm −1 corresponding to the collective band was also observed by the two-dimensional correlation Raman spectroscopy [38]. On the contrary, those of hydrophobic substances such as t-butanol [22] (molar fraction, p X = 0.04) and tetra-n-butylammonium hydroxide [23] (p X = 0.013) were higher than that of pure water, due to an enhancement of the H-bond between water molecules in hydrophobic hydration shells around the hydrocarbon moiety [39]. These results show that the vibrational band attributed to the O-H oscillators of the water cluster can be distinguished from that of the water hydrated to solutes by using the polarized Raman spectroscopy, and that this method has the ability to detect changes in the H-bonded network structure of water even in dilute or semidilute aqueous solutions (p X = 0.01-0.05, ca.…”

“…1a, the component of the O-H stretching band of water centered at 3250 cm −1 was highly polarized and diminished in the spectra at a perpendicular position [20][21][22][23][24]. It was pointed out that the contribution of Fermi resonance with bending overtones to this band [25] is not consistent with data for ice I and amorphous ice [26].…”

Clouding phenomenon and SANS studies on tetra-n-butylammonium dodecylsulfate micellar solutions in the absence and presence of salts

“…8A (see below) [19,35,45]. Water molecules around the butyl chains facing bulk water take on a highly ordered, clathrate-like structure [46]. The hydrophobic units, which do not H-bond to water, create excluded volume region where the density of water molecules vanishes.…”