Expressions for the correlation times corresponding to various models are presented which have been proposed in the literature. Experimental results fo

Structural and energy changes following the dissociation of the trans-azo-dioxide dimer of nitrosomethane into monomeric units have been studied by per

Performed in a highly polar medium, this dielectric study of the binary system Benzonitril-chloroform (at 20°C) takes into account the different type

The solvation of aluminium chloride in mixtures of nitromethane and dimethylformamide was investigated using NMR spectroscopy (proton and aluminium res The measurements were performed with a wide range of mixtures of the two solvents. Analysis of the areas, chemical shifts and line-widths of the spectr Results from 1H- and 27 Aℓ-resonance measurements could be correlated with conductivity measurements.

The far infra-red absorption spectrum of the compressed gas ethylene has been measured in the region 10–200 cm −1 at pressures from 14.7 to 55.7 bar at 296 K. The origin of the broad bands observed is a bimolecular collision induced absorption as indicated by the dependence of the total integrated intensity on the square of the molecular number density. The quantum theory [6] of resonant, multipole induction, giving rise to sets of rotational transitions is an inadequate description of the observed broad continua, the peaks of which shift from 125 cm −1 to 150 cm −1 over the pressure range investigated. However, they are matched satisfactorily by a spectral function c(ω), generated from an approximation to its related classical autocorrelation function c(t), containing two equilibrium averages K o(o) and K l(l) (which are related to the coefficients in the Maclaurin expansion of c(t)); and a width parameter γ. All three phenomenological parameters vary with pressure, contrary to the quantum prediction of their constancy, and go through a smooth minimum at ca . 30 bar, where the correlation time τ is longest.

Dielectric and ultrasonic measurements on binary mixtures of benzene with hexafluorobenzene are reported. The dielectric measurements cover the submillimetre and microwave spectral regions and the ultrasonic absorption experiments were performed at 1.5 MHz. Excess functions computed from these data are found to exhibit a maximum towards the benzene-rich mixtures. The significance of these observations is discussed in terms of the existence of small concentrations of weakly interacting species in these mixtures.

On the basis of the results obtained in a series of structure investigations and a series of theoretical studies the effect of hydrogen bonding on the peptide linkage (the NCO moiety) is discussed. The structure determinations., using X-ray diffraction methods, comprise eight molecules which contain the NCO moiety. The theoretical studies have been carried out using ab initio methods with hydrogen bonded complexes of formamide as model systems. The effect of hydrogen bonding on the peptide linkage, i.e. the shortening of the CN bond and the lengthening of the CO bond, is well reflected by the theoretical calculations. These calculations indicate that the readily delocalized π-electronic system, which can counteract perturbations in the σ-electronic system, is one of the major factors in the ability of the peptide linkage to form hydrogen bonds. On the basis of the structural parameters obtained in the crystal structure determinations and those found in the gaseous state for some simple amides, it is found that the formation of one intermolecular NH… O hydrogen bond, i.e. such that both the nitrogen and oxygen atoms of the NCO moiety are involved, leads to a shortening of the CN bond by ∼ 0.025 Å and a lengthening of the CO bond by ∼ 0.014 Å