Solutions of lithium hexafluorophosphate, LiPF 6 , in propylene carbonate (4-methyl-1,3-dioxolan-2-one; denoted by PC hereafter) in the concentration range from 0.0 to 3.29 M (M ) mol dm -3 ) have been studied regarding their conductivities, viscosities, and self-diffusion coefficients of PC by the NMR field gradient technique, Raman spectra, and NMR spectra. Walden's products are almost constant in the range up to and over 3.0 M. Therefore, Li ions are considered to be quite free from the firm interaction with anions even in such concentrated solutions. The appearance of the maximum conductivity at about 0.8 M is explained by associating with the concentration dependence of the solution viscosity. A remarkable increase in the solution viscosity was observed in a concentration beyond 2.0 M, and it can be ascribed to the cluster formation of lithium ions with PC molecules of the solvent. Such an idea of clusters can reasonably interpret some of the characteristic changes of the viscosities, the diffusion coefficients, the Raman spectra, and the NMR spectra at concentrations over 2 M.

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The keto-enol tautomerism of phenylpyruvic acid, (p-hydroxyphenyl)pyruvic acid, and salts of the former compound was investigated by IR and Raman spectroscopy. The spectral data indicate that these acids take the enol form in the solid state. The enol is predominant in organic media also. The IR strong band at 1620 cm"1 in the solid acids is not originated from the C=C stretching vibration, but the weak band around 1660 cm"1, which has a very strong Raman counterpart, is assignable to it. O-deuterated phenylpyruvic acid also shows similar bands. The 1620-cm"1 band is not observed in solution. A possible structure which explains these spectra was proposed. The Raman spectra of salts of phenylpyruvic acid do not exhibit any C=C bands, indicating their existence in the keto form. However, no keto C=0 band is observed in the IR spectra of the hydrated sodium and lithium salts, whereas the typical C=0 band is found in the anhydrous sodium salt and the potassium and calcium salts. The drastic changes in the IR spectrum of the hydrated sodium salt on dehydration and in that of the lithium salt on O-deuteration suggest that these hydrated salts have the gezn-diol structure in the solid state. It was found by NMR that the normal keto form is more stable in aqueous solution irrespective of the nature of the metal cation involved.

The infrared and Raman spectra of 2-azetidinone and its 1-d, 3,3-d2, and 1,3,3-d3 and their 15N compounds have been recorded, and the observed bands have been assigned on the basis of the isotope effects and the normal coordinate analysis. The refined force constants have reproduced the observed frequencies satisfactorily. The C–N stretching mode is strongly coupled with the N–H bending vibration to give a band near 1380 cm−1. However, this coupling does not give rise to any bands corresponding to the amide II and III bands. The concentration dependence of the infrared spectrum suggests the presence of an equilibrium of monomer \leftrightharpoons cyclic dimer in carbon tetrachloride solution. The solvent effects on the N–H and C=O stretching bands have also been examined.