Synthetic Applications of Heteroaromatic Betaines with Six-Membered Rings

The cycloadditions of 3-hydroxy-1-methylpyridinium betaines with electron-deficient olefins have been extended to a variety of 1-substituents in place of methyl. Application of resonance theory and later of quantum chemical methods led to rationalization of preceding results and prediction of new reactions. Thermal additions of 2π- and 6π-electron addends at the 2,6-positions and of 4π-electron addends at the 2,4-positions are described. The cycloadducts are highly interesting potential synthetic building blocks.     

Low frequency vibrations in crystalline biphenyl: Model calculations and raman and neutron spectra

Vibrational frequencies of crystalline biphenyl have been calculated in the rigid phenyl approximation using the crystal structure at 110 K. The calculated results explain successfully the experimental infrared and Raman frequencies as well as the polarization data of the Raman bands at 80 K that have been observed in the present study for the first time. The frequency dispersion curves calculated in the b^* direction show that the coupling between the intramolecular CC torsion and the translational lattice vibrations changes drastically as the wave vector changes. The existence of a minimum frequency point located away from the Brillouin zone boundary indicates that the pulse transition near 40 K is a commensurate—incommensurate one in accordance with the results of neutron diffraction that have recently been reported. Incoherent inelastic neutron scattering spectra have also been investigated above and below the phase transition temperature.     

Determinations of traces of calcium in phosphoric acid and its salts by atomic-absorption spectrometry

A method for the determination of traces of calcium by atomic-absorption spectrometry after extraction into an organic solvent, has been investigated for the determination of traces of calcium in phosphoric acid and its salts. Calcium is extracted as the hydroxy-quinolate complex, the extract is introduced into the flame, and the calcium atomic-absorption is measured. The effects of pH, concentration of reagent, and diverse ions on the calcium extraction were investigated.     

Rotational analysis and radiative lifetime measurement on the 2B1 (K′ = 0) excited state of NO2 with v′2 = 6, 7, 8, and 9

The rotational structure of the ²B₁ (K′ = 0) subbands of NO₂ with v′₂ = 6, 7, 8, and 9 were analyzed by means of the time-gated excitation spectrum. The excitation spectrum monitored at ν₂, 2ν₂, or 3ν₂ fluorescence band was fairly simplified in comparison to its corresponding absorption spectrum. The band origins and rotational constants are evaluated from the observed data: ν₀ = 20205.0 cm^?1, $\text{B}\text{′ = 0.374}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 6; ν₀ = 21104.4 cm^?1, $\text{B}\text{′ = 0.374}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 7; ν₀ = 22001.9 cm^?1, $\text{B}\text{′ = 0.375}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 8ν₀ = 22898.0 cm^?1, $\text{B}\text{′ = 0.375}\text{cm}{}^{\mathrm{?1}}$ for v′₂ = 9. The value of $\text{B}\text{′}$ extrapolated to v′ = 0 is 0.370 cm^?1. This value corresponds to the bond length of 1.19 Å. Fluorescence decays of these excited levels were also studied. Radiative lifetimes obtained by extrapolation to zero pressure from the $\text{1}\text{τ}\text{– P}$ plots were 25–40 μsec. The short-lived excited levels previously reported by some authors were not found.     

Carbon-13 NMR study of substituted benzyl N,N-dimethylcarbamates

The ¹³C NMR chemical shifts of m- and p-substituted benzyl N,N-dimethylcarbamates were measured in CDCl₃. The meta and para ¹³C substituent chemical shifts were analysed by means of dual substituent parameter (DSP) equations. Good correlations were obtained, especially for the para-carbon substituent chemical shifts. The computed transmission coefficients, ρ_I and ρ_R, are consistent with the general features of the fitting parameters. It has been shown that no significant electron demand is imposed by the ? CH₂OCON(CH₃)₂ substituent.     

Use of crosslinked polysiloxane stationary phases in open-tubular capillary liquid chromatography

Crosslinked polysiloxane stationary phases were prepared on soda-lime glass capillaries and applied to the separation of polynuclear aromatic hydrocarbons and of phthalates in reversedphase liquid chromatography. Preparation procedures and chromatographic performance of these columns are described.     

Long range 13C?1H coupling constants IV—methoxy-, amino- and hydroxypyridines

One bond and long range ¹³C? ¹H coupling constants for some methoxy-, amino- and hydroxypyridines are described. An unambiguous assignment of carbon-13 resonances is carried out based on the analysis of the fine splitting caused by long range couplings. J values for compounds other than 2- and 4-hydroxy-pyridines are explainable in terms of the values previouly obtained for cyano- and methylpyridines. The hydroxypyridine-pyridone tautomerism affects ²J(H_α), i.e. ²J associated with the α proton. This effect can be used to differentiate pyridones from hydroxypyridines.     

Quantum filter for nonlocal polarization properties of photonic qubits

We present an optical filter that transmits photon pairs only if they share the same horizontal or vertical polarization, without decreasing the quantum coherence between these two possibilities. Various applications for entanglement manipulations and multiphoton qubits are discussed.