W. Alexander Van Hook

Isotope Effects on Internal Frequencies in the Condensed Phase Resulting from Interactions with the Hindered Translations and Rotations. The Vapor Pressures of the Isotopic Ethylenes

Interaction of the hindered translations and rotations with the internal vibrations in the condensed phase leads to isotope‐dependent shifts of the internal frequencies. This isotope dependence is a necessary consequence of the fact that the coordinates representing the translations and rotations of the molecule as a whole are, in general, isotope dependent. This external—internal interaction is investigated and the XH2 system is employed as a simple example to demonstrate the nature of the interaction. It is shown that the experimentally determined vapor pressures of the isotopic ethylenes may be rationalized when the external—internal interaction is taken into account. A force field based on a simple cell model for liquid ethylene is obtained which yields good agreement with the experimentally determined vapor‐pressure isotope effects. The force field, while not unique, fits (and is in fact partially based on) other available data on liquid ethylene.

Apparent molar volumes, isobaric expansion coefficients, and isentropic compressibilities, and their HD isotope effects for some aqueous carbohydrate solutions☆☆☆

Abstract The molar volumes, isobaric expansion coefficients, and isentropic compressibilities of solutions of a number of carbohydrates and their deuterated isomers were determined in H 2 O and D 2 O between 288.15 and 328.15 K and over a wide range of solute-to-solvent mole ratios. The results are discussed in terms of the specific hydration model.

Liquid-liquid demixing from solutions of polystyrene. 1. A review. 2. Improved correlation with solvent properties

Low pressure liquid–liquid demixing data for polystyrene dissolved in 76 different one‐component solvent systems are reviewed and correlated. The phase diagrams are discussed. With only one exception the molecular weight of each solvent is less than that of two polystyrene monomer units. A new relation is developed which quantitatively correlates the area of solubility lying between the UCS and LCS demixing curves in the (Tc, Mw−1/2) projection with solvent solubility parameters.

Vapor Pressures of the Deuterated Ethanes

The vapor pressures of all 10 deutero—protio‐ethane isomers C2HiD6—i (0≤i≤6) have been measured over the temperature range 115° to 200°K [∼1 mm C2H6 to 1600 mm C2H6] by direct manometry. The isotope effects are inverse and go through maxima between 125° and 140°K. At the maxima they are on the order of 1.2% per D atom. Deviations from the law of the mean are small, but for the three sets of equivalent isomers 1,1‐ and 1,2‐C2H4D2; 1,1,1‐ and 1,1,2‐C2H3D3; and 1,1,1,2‐ and 1,1,2,2‐C2H2D4 significant differences in vapor pressure are observed. The more unsymmetrically substituted compound has the higher vapor pressure in all cases.The data are interpreted in the light of the statistical theory of isotope effects in condensed systems. A model calculation is made within the framework of this theory in its harmonic‐cell approximation using reasonable force fields. It is necessary to invoke temperature‐dependent force constants for the low‐energy (u=hv/kT<2π) modes in order to rationalize the temperature depende...

A new apparatus for the detection of phase equilibria in polymer solvent systems by light scattering

New equipment designed to measure the effect of pressure and isotopic substitution on liquid/liquid equilibria in polymer/solvent systems is described. The phase separation is detected by monitoring low‐angle forward scattered light, together with simultaneous loss in transmitted light, from an He–Ne laser shining through the sample. Phase transitions can be induced by varying temperature/time and/or pressure/time profiles or by a combination of such changes. The system operates at high precision (±0.001 K, ±0.002 MPa), and over wide temperature and pressure ranges (240≤T/K≤600, 0.01≤P/Mpa≤35). The temperature, pressure, and transmitted and scattered light intensities are digitally recorded, and the rate of change of the temperature and/or pressure used to induce the phase transition is under computer control. The system is being used to study the temperature, pressure, polymer molecular weight, and molecular weight distribution, and H/D dependences of phase equilibria for polystyrene (PS)/(CH3)2CO and PS...

Vapor pressures, liquid molar volumes, vapor non-idealities, and critical properties of some fluorinated ethers: CF3OCF2OCF3, CF3OCF2CF2H, c-CF2CF2CF2O, CF3OCF2H, and CF3OCH3; and of CCI3F and CF2CIH

Vapor pressures, compressibilities, expansivities, and molar volumes of the liquid phase have been measured between room temperature and the critical temperature for a series of fluorinated ethers: CF 3 OCF 2 OCF 3 , CF 3 OCF 2 CF 2 H, c -CF 2 CF 2 CF 2 O, CF 3 OCF 2 H, and CF 3 OCH 3 . Vapor-phase non-idealities were measured for each compound, but only for samples of high vapor density. Critical temperatures and pressures and approximate melting and boiling temperatures are reported. Apparatus calibrations were checked with measurements on the well characterized materials: CFCl 3 , (R11) and CF 2 ClH (R22).

Vapor pressures, liquid molar volumes, vapor non-ideality, and critical properties of some partially fluorinated ethers (CF3OCF2CF2H, CF3OCF2H, and CF3OCH3), some perfluoroethers (CF3OCF2OCF3, c-CF2OCF2OCF2, and c-CF2CF2CF2O), and of CHF2Br and CF3CFHCF3

Recent measurements of the thermophysical properties of some fluorinated ethers (CF 3 OCF 2 CF 2 H, CF 3 OCF 2 H, CF 3 OCH 3 , CF 3 OCF 2 OCF 3 , and c -CF 2 CF 2 CF 2 O), from around room temperature to the critical region ( J. Chem. Thermodynamics 1991 , 23, 699) have been exteaded to T = 235 K. New measurements for c -CF 2 OCF 2 OCF 2 , CHF 2 Br, and CF 3 CFHCF 3 are reported from the temperature 235 K to the critical temperature, and for c -CF 2 CF 2 CF 2 O at temperatures from 235 K to 273 K. Improvements are reported in the earlier method for determining vapor-phase virial coefficients. Vapor pressures, liquid- and vapor-phase molar volumes, compressibilities, expansivities, virial coefficients, critical temperatures and pressures, and approximate melting temperatures are reported.

The effect of H/D substitution and pressure on the liquid–liquid equilibrium between cyclohexane and methanol

Coexistence curves for the systems C6H12+CH3OH(i), C6D12+CH3OH(ii), C6H12+CH3OD(iii), and C6H12+CD3OD(iv) have been studied as a function of pressure [0.1<(P/MPa)<13] and reduced temperature t=(1−T/Tc) (0<t<1.3×10−2). A multiple sample technique was employed. The amplitudes and critical exponents and their pressure and isotope dependences are reported. The effect of isotopic dilution of each component on the critical solution temperature Tc has also been studied. The critical exponents show neither isotope nor pressure dependence. Critical temperatures show singnificant isotope dependence [Tc(i)−Tc(ii)]= i−ii=3.91 K, i−iii=−2.50 K, i−iv=0.23 K, and a significant pressure dependence dTc/dP=0.317 K/MPa, which over the range of conditions is independent of pressure and isotopic substitution. The amplitude factors, which carry larger experimental errors, show both isotope and pressure dependences. Isotopic dilution studies were carried out only at ambient pressure. Their interpretation leads to the conclusion...

Liquid–liquid equilibria in polymer solutions at negative pressure

Properties of liquids under tension (i.e. at negative pressure) are discussed together with methods of producing negative pressure. That established, the pressure dependence of liquid–liquid demixing in certain polymer–solvent solutions, including demixing at negative pressure is described.

Vapor pressure isotope effects in aqueous systems. VIII. The system dimethyl sulfoxide/H2O/D2O

AbstractVapor pressures for the system I (dimethyl sulfoxide/H2O=DMSO/H2O) and isotopic differential pressures I-II (II=DMSO/D2O) have been measured between 25 and 70°C at DMSO concentrations of 0.05, 0.15, 0.30, 0.45, 0.60, 0.70, 0.80, 0.87, and 0.92 mole fraction. A high-precision differential method was used. The total pressures over the solutions, I, have been fitted to a relation derived from the Duhem-Margules equation, PT=P1oX1γ1+P2oX2γ2, with γ1=exp[∑kαkX2k] and