Low-frequency Raman spectra from concentrated aqueous hydrochloric acid: normal-coordinate analysis using a "four-atomic" model of Cs symmetry, (H2O)2(H3O+)(Cl-H2O)

Abstract

9127 (1 3) Girard, P.; Couffignal, R.; Kogan, H. B. Terruhedron Lerr. 1981,22, (14) Wolfe, S.; Pilgrim, W. R.; Garrard, T. F.; Chamberlain, P. Can. J. (15) Baranovic, G.; Colombo, L.; Furic, K.; Durig, J. R.; Sullivan, F.; (16) Hoshi, T.; Okubo, J.; Kobayashi, M.; Tanizaki J. Am. Chem. SOC. (17) Dale, W. J.; Starr, L.; Sterobel, C. W. J. Org. Chem. 1961, 2225. (18) Hashimoto, S.; Shimojima, A.; Yuzawa, T.; Hiura, H.; Abe, J.; (19) Kunimatsu, N.; Takahashi, H. To be published. (20) Colombo, L.; Kirin, D.; Volovsek, V.; Lindsay, N. E.; Sullivan, J. F.; 3959.Low-frequency, X ( Z 2 ) Y, X(ZX) Y, and isotropic, BoseEinstein corrected, Raman spectra were obtained from concentrated aqueous HCl. Normal-coordinate analysis of the intermolecular vibrational frequencies was carried-out with a "four-atomic" (H20)2(H30+)(CI-Hz0) model of C, symmetry using structural parameters obtained from X-ray RDF data. The C1-ion is directly hydrogen-bonded to one of the protons of H30+ in this structure, i.e., one C1-is interspersed between, and hydrogen-bonded to both, a proton of H30+ and an outer H20. The C, structure fits the Raman data when [H20 [HCI] RDF peaks' as the two 0 4 1 distances of the C, structure. These two 0-C1 distances and the 0-0 RDF distance of 2.52 A place the C1-above the three protons, Le., the line from the 0 of H30+ to C1-differs only =9O from the 3-foid axis of H30+. This C, model is analogous to that used by Gigu5re2 to explain the weakness of HF, but the hydrogen bonding between C1-and H30+ is much weaker than that between F and H30+, in accord with the greater acid strength of HCl. < 4, whereas H904+ fails to explain a key isotropic feature. The C, model also explains both of the 3.13-and 3.63-u X-ray I ,

Picosecond Proton Transfer Kinetics in Water Revealed with Ultrafast IR Spectroscopy

“…Our polarization dependence is consistent with the anisotropic Raman response, and is reminiscent of the recurrence seen at 200 fs in the impulsive Raman response in neat H 2 O . Water and HCl solutions both display Raman active modes at this frequency, ,, which could originate from a number of intermolecular degrees of freedom that are coupled to and aligned with the hydrated proton bend transition moment.…”

Decomposition of the Experimental Raman and Infrared Spectra of Acidic Water into Proton, Special Pair, and Counterion Contributions

“…The prominent Raman band at very low frequencies (below 200 cm −1 ) in Figure 2a−c has previously been attributed to the "anisotropic proton polarizability of the hydrogen bonds in H 5 O 2 + groupings". 19 However, our results shown in Figure 2c, as well as those of previous studies, 37,38 indicate that NaCl solutions also produced enhanced intensity in this region; thus, both the hydrated proton and its counterion contribute to low- frequency Raman scattering that is enhanced relative to pure water. With regard to the high-frequency OH stretch region (at ∼3300 ± 300 cm −1 ), our additional polarized Raman-MCR measurements reveal a rather abrupt increase in depolarization ratio above ∼3200 cm −1 (see Figure S8), indicating that the low-and high-frequency portions of the hydrated proton OH stretch band arise from structurally distinct configurations.…”

Local Structure of Li+ in Concentrated Ethylene Carbonate Solutions Studied by Low-Frequency Raman Scattering and Neutron Diffraction with 6Li/7Li Isotopic Substitution Methods

“…Raman scattering intensities were measured at 1 cm –1 intervals in both the parallel and perpendicular polarization modes with a spectral slit width of 5 cm –1 . Observed parallel and perpendicular spectra were converted to the reduced intensity, which is proportional to the square of the polarizability change during the vibration. − where ν and ν 0 denote the Stokes Raman shift and wavenumber of the incident light, respectively. h and k stand for the Planck constant and the Boltzmann constant, respectively.…”