Hydration and Seamless Integration of Hydrogen Peroxide in Water

Abstract

Raman multivariate curve resolution is used to decompose the vibrational spectra of aqueous hydrogen peroxide (H2O2) into pure water, dilute H2O2, and concentrated H2O2 spectral components. The dilute spectra reveal four sub-bands in the OH stretch region, assigned to the OH stretch and Fermi resonant bend overtone of H2O2, and two nonequivalent OH groups on water molecules that donate a hydrogen bond to H2O2. At high concentrations, a spectral component resembling pure H2O2 emerges. Our results further demonstrate that H2O2 perturbs the structure of water significantly less than either methanol or sodium chloride of the same concentration, as evidenced by comparing the hydration-shell spectra of tert-butyl alcohol dissolved in the three aqueous solutions.

Experimental Confirmation of H2O2 Adsorption at the Water–Air Interface

“…28 Nevertheless, studies of H 2 O 2 − H 2 O solutions have generally concluded that these solutions are close to ideal, at least in the liquid state. 6,28 The modest value of hydrogen peroxide's standard adsorption free energy is certainly consistent with these other properties.…”

“…As discussed above, the GARS probe depth is expected to be considerably deeper than the upper 5−10 A in the surface region, most likely exploring the same depth profile as surface tension measurements. The "seamless integration" of H 2 O 2 into the water structure, 6 due to From the slope and intercept, the kinetic equilibrium constant is obtained. (b) Plot of the data, fit using eq 4.…”

“…As discussed above, the GARS probe depth is expected to be considerably deeper than the upper 5–10 A in the surface region, most likely exploring the same depth profile as surface tension measurements. The “seamless integration” of H 2 O 2 into the water structure, due to its very similar hydrogen bonding ability, makes extraction of hydrogen peroxide surface excess from surface tension measurements problematic, however. Nevertheless, given the results presented here, we may say with some confidence that H 2 O 2 is enriched in the surface region of aqueous solutions.…”

“…The similar structures and hydrogen bonding abilities of water and hydrogen peroxide suggest that any surface propensity would be weak at best. Indeed, a very recent study by Bredt et al, 6 concludes that there is "seamless integration" of hydrogen peroxide into the water structure. Nevertheless, results of Molecular Dynamics (MD) simulations reported in 2004 by Vacha et al 7 suggested an adsorption free energy of about −4 kJ mol −1 for H 2 O 2 at the water surface.…”

Chemical Morphology Controls Reactivity of OH Radicals at the Air–Ice Interface

“…Anthracene is seen to exist in clumps at the interface, rather than being evenly distributed there, covering only 7% of the surface at amounts that would nominally form a monolayer . The observation that there is not significant fluorescence quenching of pyrene by hydrogen peroxide at the ice surface further suggests that the highly soluble hydrogen peroxideexpected to be homogeneously distributed at the interfaceis not in effective contact with the much less soluble pyrene. Hydrogen peroxide shows only a very mild freeze-concentration effect, suggesting that this highly soluble species is evenly incorporated into the ice and liquid portions.…”