Showing papers in "The Journal of Physical Chemistry in 1963"

The importance of active surface area in the carbon-oxygen reaction1,2

Abstract: Graphon, a highly graphitized carbon black, was oxidized to seven levels of burn-off between zero and 35%. The active surface area of the oxidized samples was determined by measuring the coverage of the surface with oxygen complex upon exposure of the samples to O2 at 300 deg for 24 hr. After removal of the complex, the Graphon samples were subsequently treated with additional O2. The amount of oxygen complex formed on the surface during reaction could be followed by a material balance and at the end of a run by outgassing. From the data, unoccupied active surface areas were calculated. Rate constants for O2 depletion and product formation, calculated on the basis of unoccupied active area, were essentially constant over most of the burn- off range studied. On the other hand, rate constants, calculated on the basis of BET surface area, showed a considerable increase with burn-off.

On the theory of oxidation—Reduction reactions involving electron transfer. V. Comparison and properties of electrochemical and chemical rate constants

Abstract: Using a theory of electron transfers which takes cognizance of reorganization of the medium outside the inner coordination shell and of changes of bond lengths inside it, relations between electrochemical and related chemical rate constants are deduced and compared with the experimental data A correlation is found, without the use of arbitrary parameters Effects of weak complexes with added electrolytes are included under specified conditions The deductions offer a way of coordinating a variety of data in the two fields, internally as well as with each other, and a way of predicting results in one field from those in another For example, the rate of oxidation or reduction of a series of related reactants by one reagent is correlated with that of another and with that of the corresponding electrochemical oxidation-reduction reaction, under certain specified conditions These correlations may also provide a test for distinguishing an electron from an atom transfer mechanism

THE AQUEOUS SOLUTION BEHAVIOR OF LARGE UNIVALENT IONS. A NEW TYPE OF ION-PAIRING1a

Abstract: For large, unhydrated, univalent ions, a tightening of the surrounding water structure is a dominant feature of their aqueous solution behavior. As represented by their activity and osmotic coefficients, this corresponds to a rise in the coefficients above the Debye-Huckel limiting law, and the increase is larger, the larger the ion, but if both the cation and anion are such large hydrophobic ions, the hydrogenbonded water structure forces them together to maximize the water-water interactions and to minimize the disturbance to itself. This water structure-enforced ion-pairing is every different from the more usual electrostatic, or Bjerrum, type of ion-pairing, occurring oniy in water, or other highly hydrogen-bonded solvents, and being greater, the larger the ions and the smaller their charges. Some chemical results of this type of ion-pairing are discussed. (auth)

N.m.r. spin-echo self-diffusion measurements on fluids undergoing restricted diffusion

Abstract: Spin-echo measurements are carried out on self-diffusion of water in geological cores and in aqueous suspensions of silica spheres. Spin-echo measurements of the diffusion of benzene in rubber are also carried out. (T.F.H.)

Topological aspects of the conformational stability problem. part i. degenerate electronic states1

Abstract: ? 8 8 9 2 ; enner electronic potential energy surfaces of symmetric polyatomic systems is derived by means of group theoretic and permutational symmetry principles. Degenerate penturbation theory is utilized to obtain an explicit analytical expression of this topography. The dependence of the nuclear-electronic interaction matrix elements, which occur in the penturbation development, on the nuclear coordinates is shown to be precisely determinable by group theoretic and permutational symmetry technlques. The numerical coefficients which prefix the nuclear coordinates which appear in these interaction matrix arrays are regarded as phenomenological parameters in their subsequent topographical applications. It is demonstrated that the magnitudes of these parameters determine only the relative placements of the Jahn-Teller- Renner surface reliefs and not their basic character (in this sense, minimal and maximal domains are taken to be of the same character). The formulas derived by means of the penturbation theory (with and without the complication of spin-orbit interactions) are employed to describe the topology of the multiply degenerate electronic energy surfaces of the regular polygons (including the digon) and the regular polyhedra, as well as of a number of selected highly symmetric irregular polygons and polyhedra. The results obtained reveal a number ofmore » important maxims: (1) the Jahn- Teller- Renner behavior of a polyatomic group theoretic system is completely determined by that of its elemental subgroups (principle of mathematical inheritance); (2) isomorphous point groups exhibit isomorphous Jahn- Teller deportments (formation of Jahn- Teller families); (3) whereas the prime number groups produce a single unique Jahn- Teller- Renner topography, the non- prime number groups produce all those topographies which are required by the principle of mathematical inheritance (1) (law of prime numbers); (4) the dynamical quantization and the topography of the Jahn-Teller problem are completely specified by group theoretic and permutational symmetry precepts (symmetrical transcendence); (5) although not mathematically required, the symmetry of the stable Jahn- Teller conformation is always the highest symmetry which is yet compatible with the loss of the initial inherent degeneracy (mimimax rule); (8) the Jahn- Teller- Renner energy resolvants factor only at locations of high nuclear symmetry (factorization theorem); (7) certain nuclear structures can never be JahnTeller stabilized (exclusion principle); (8) it is impossible to distinguish between ordinary anharmonic elastic distortions and Jahn-Teller distortions in non-homologous series of compounds (indistinguishability theorem), (9) spin-orbit forces remove cuspidal Jahn-- Teller radial electroric energy singularities for geometries less regular than the cube (spin-orbit law); (10) ionic and covalent bonding forces always produce complementary Jahn- Teller deformations, whereas conjugate hole-electron electronlc configurations always produce the identical deformation, bonding forces being equal (complementarity rules); (11) pseudo-JahnTeller interactions make conformational isomerisms possible even for dispositions of low regularity (conformational isomerization tenet); (12) doubly degenerate electronic states possess continuous Jahn- Teller- Renner electronic energy surfaces, but triply degenerate electronlc states possess disjoint electronlc energy surfaces in centain directions (canon of dimensional variability); (13) tetragonal Jahn- Teller conformational interconversion takes place in two dimensions for doubly degenerate electronic states, and five dimensions for triply degenerate electronlc states (doctrine of dimensional impenetrability); (14) experimental proofs of Jahn- Teller- Renner consequences can only be obtained from studies of homologous series of compounds (criterion of probity). Panticular care was taken to graphically illustrate all the important consequences of the« less

The three electron (or hole) cubic ligand field spectrum1

Abstract: $^{1}$ a) W A Runciman, private communications (1961 and 1962); b) K A Schroeder, private communication (1962), J Chem Phys 37, 2553 (1962), and to be published $^{2}$ A D Liehr, J Phys Chem 64, 43 (1960) $^{3A}$ D Liehr and C J Ballhausen, Ann Phys (NY) 6, 134 (1959) $^{4}$ A D Liehr, J Phys Chem 67, 1314 (1963) $^{5}$ A D Liehr, Symposium on the Structure and Properties of Coordination Compounds, Smolenice, Czechoslovakia, September 2-4, 1964 $^{6}$ A D Liehr, Symposium on Coordination Chemistry, Tihany, Hungary, September 14-17, 1964 (submitted)

Nuclear transfer and anisotropic motional spin phenomena: relaxation time temperature dependence studies of water adsorbed on silica gel. iv

Abstract: An experimental investigation of the temperature dependence of the nuclear magnetic resonance relaxation phenomena of water vapor adsorbed on silica gel is described. Two-component relaxation data are observed. With temperature increase, the longer T/sub 2/ value decreases while its fractional population increases. These data are shown to be consistent with nuclear transfers between two state environments possessing distinct relaxation characteristics. and a comparison with theory is made. Evidence of a change of surface characteristics is presented; for early experiments, two-component longitudinal relaxation occurs below a transition temperature; in later experiments, only one-component T/sub 1/ behavior is found. A theory for an anisotropic motional model for nuclear magnetic dipole-dipole relaxation on surfaces is presented. The motional model is random reorientation of the interproton vector about an axis normal to the surface that occurs much faster than the time dependence of the angle between the vector and this axis. The relaxation processes are thus related to multiple nuclear correlation times. Consequences of an anisotropic model agree with experimental observations. (auth)