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 ,