Path-integral computations of tunneling processes

The application of the path-integral methodology of Chandler and Wolynes [D. Chandler and P. G. Wolynes, J. Chem. Phys. 74, 4078 (1981)] to the calculation of one-electron-tunneling probabilities is revisited. We show that the evaluation of the kink free energy that is related to the tunneling splitting is associated with "polymer bead" distributions over a continuous distribution of scaled barriers, which makes both the calculation and its physical interpretation relatively difficult. In particular, we find that relative to other available techniques the method converges slowly and suffers from inaccuracies associated with the finite-temperature aspect of the calculation, and that past tentative identification of the bead distribution over the barrier with a physical picture of a "tunneling path" should be reassessed.     

Ionic conductivity of anhydrous zirconium bis(monohydrogen orthophosphate) and its sodium ion forms

Conductivities have been measured by the vector impedance method for the layered compounds anhydrous α-zirconium phosphate, Zr(HPO₄)₂, and several of its sodium ion phases. The values of the ionic diffusion coefficients are of the order of 10^?6-10^?8 cm²/s at 200°C and activation energies range from 15.6 cal/mol for Zr(HPO₄)₂ to 18.6 cal/mol for ZrHNa(PO₄)₂. Comparisons are made with literature values of conductivity and self-diffusion coefficients for Zr(NaPO₄)₂·3H₂O and kinetically determined diffusion coefficients for the phases containing both sodium and hydrogen ions.     

Synthesis of spin-labeled analogs of dihydroxyaminoalkylaminoanthraquinone

Synthesis of spin labeled analogs of antineoplastic dihydroxyaminoalkylaminoanthraquinones is described.     

Ordered surface phases

We give a simple proof of the coexistence of an ordered surface phase with a disordered bulk one.     

Ordered differential fields

We introduce the abstract notion of an ordered differential field and show that some of the basic asymptotic growth properties of differentiable functions can be discussed within this setting. However, in order to ensure that log x → ∞ as x → ∞, we have to assume that the field of constants is archimedean.     

Rotational isomerism—XVI: The AA′BB′X NMR spectrum and rotational isomerism of 2-fluoroethyl trichloroacetate

The complete AA′BB′X analysis of the ¹H and ¹⁹F NMR spectrum of CH₂F.CH₂OCO·CCl₃ ( 1 ) as a neat liquid and in various solvents is given and considered in detail. The differentiation of the two conjugate solutions is obtained both from the X spectrum and by analysis at two field strengths. The coupling constants obtained show that the compound exists almost entirely in the gauche rotamer in all solvents.     

Formation and amination of dibenz[b,f,-1]azapen-talene dianion: Attempted synthesis of dibenz[b,f,-1]azapentalene

Dibenz[b, f,-1]azapentalene dianion (3) was allowed to react with N,N diethyl - O - mesitylenesulfonylhydroxylamine (4) in order to obtain N,N - diethyl - 5,10 - dihydroindeno[1,2 - b] - indol - 10 - amine (11). The available data indicated that electron transfer processes were involved in the formation of 11. Attempts to obtain dibenz[b, f,-1]azapentalene (1) and 11 by Hofman elimination or by the reaction of 11 with trifluoroacetic acid were unsuccessful.     

Prediction of latent heat of vaporization of multicomponent mixtures

A very simple method has been developed for predicting the differential latent heat of vaporization involved in vapor-liquid equilibria of multicomponent mixtures. The technique uses the UNIFAC method for predicting activity coefficients.In order to establish this method, 88 binary systems and 13 ternary systems, both nonazeotropic and azeotropic, were tested successfully. On the basis of the 101 systems investigated, the mean overall deviation between the observed and predicted values was found to be 4.6%. Despite the fact that the majority of the systems tested were azeotropic, a consequence of the small amount of data available for the differential heats of nonazeotropic systems, the method proposed is equally applicable to nonazeotropic systems.For azeotropic mixtures, it is possible to predict the latent heat (integral or differential) by means of an analytical equation which involves only the parameters of Antoine's equation, with a mean overall deviation of 6.1%.From the differential heats obtained by the proposed method, it is possible to calculate integral heats by applying equations derived here which relate these quantities.