Investigation of association reactions in polar gases using the pressure and temperature dependence of thermal conductivity

Abstract

abc # 0, eq 6 represents the linearly forced harmonic oscillator. Pechukas and Child3 showed analytically that the (pf,c@, curve for this system was a circle displaced from the phase space origin. Now, trajectory calculations with c = 0 and abd # 0 yield an elliptical @f,gf),i curve with center at the origin and rotated axes for the quadratically forced harmonic oscillator.% Such a phase space picture is isomorphous to that obtained for the overlap integral between harmonic oscillators with identical equilibrium positions but different force constants, kl = 1 and k2 # 1. The functional form for these overlap integrals is well-known, and the phase space pictures suggest that it may be related to the less tractable expressions for the transition probabilities obtained by Lewis and Riesenfeld% for the harmonic oscillator with time-dependent force constant. Such an oscillator is a possible model for experimentally observed30 non-Landau-Teller behavior in Ar + CsI scattering.Whether used to explain results from sophisticated CID calculations or to suggest links between simple theoretical models, classical S-matrix phase space pictures appear to be an easily employed theoretical tool worthy of continued application and development. P.M.H. is indebted to the DowThe results of investigations into the association reactions occurring in polar gases by analysis of the pressure and temperature dependence of thermal conductivity are reviewed. The gases studied include water, methanol, ethanol, 2-propanol, 2-methyl-2-propano1, 2,2,2-trifluoroethanol, acetone, acetonitrile, pyridine, acetic acid, trifluoroacetic acid, as well as the binary mixtures methanol-water, trifluoroethanol-water, and acetic acid-water. The prewure and temperature ranges of these studies are 100-2000 torr and 33&440 K, respectively. Expressions for the thermal conductivity of reacting gases derived by Butler and Brokaw, based on the work of Hirschfelder, give calculated thermal conductivities which fit the observed data very well for all the types of observed pressure dependence. The fits yield information on the associated species present (e.g., dimer, trimer, tetramer, etc.), on the concentrations of the species, and on their enthalpies and entropies of association. The thermodynamic results, in conjunction with ab initio molecular orbital calculations, provide information on the strength and structure of hydrogen bonding occurring in the cluster species.

Dimers of 1,8a-Dihydro-1,8-Naphthyridine Derivatives as Models of Chiral Self-Recognition

“…The interaction energies range between −8.87 and −13.12 kcal/mol, the smallest interaction energy being that of the homochiral complexes of the tbutyl derivative and the largest one that of the heterochiral fluorine derivative dimer. Considering that two HBs are formed in these complexes, the average contribution of each one is −5.9 kcal/mol which is similar to the interaction ene/rgy obtained experimentally in the water dimer (−5.4 kcal/mol) [30].…”

Heat capacity and corresponding states in alkan-1-ol–n-alkane systems

“…The dominance of tetramers for all alkan-1-01s is consistent with the gas-phase thermal conductivity results of ref. (5) for methanol and ethanol. These refer to much lower concentrations that can be used in solution phase and show that trimers are unimportant, while dimers only begin to show up at 5 x mol dm-3, i.e.…”

“…The Kt were tentatively related to an equilibrium constant3 for the succession of (i-1) hydrogen-bonding steps forming the i-mer, i.e. 5 ) where K refers to a single hydrogen bond and is independent of i. This suggestion was not borne out by the data,2 which required the retention of independent Kf for the different i-mers (in practice dimers, trimers and tetramers).…”

Monomer, clusters, liquid: an integrated spectroscopic study of methanol condensation

“…Although the exact distribution and the properties of these n-mers are still not established, the physical and transport properties of methanol vapor can only be understood by invoking their presence. [1][2][3][4][5][6][7][8][9][10][11] Equilibrium constants derived by fitting thermal conductivity [6][7][8] and heat capacity 3 measurements above room temperature suggest that the vapor phase consists primarily of monomers, dimers, and tetramers, while a vapor phase comprising monomers, trimers, and octamers provides a better fit for vapor pressure measurements near room temperature. 11 Complementary low temperature infrared (IR) spectroscopy experiments, 12,13 where rotational temperatures are as low as B5 K, are able to observe distinct peaks for the monomer through tetramer.…”