bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of the Faradaic Impedance at Solid Electrodes and the Electrodeposition of Copper
Authors: Bockris J. O'M. , Conway B. E. 
Published: January 2005

The techniques of pre-electrolytic purification of the solution and the maintenance of electrodes in glass sheaths until after immersion in the purified electrolytic solution have been applied for the determination of the properties of the ac impedance at the copper-solution interface. Measurements of double layer capacity and resistance at copper interfaces in H2SO4 and in CuSO4 solution over a considerable potential range have been made at frequencies from 10 to 2000 cps.
Significant results can only be obtained with careful elimination of screening and unsymmetry effects in the cell, and by the use of spherical electrodes. The double layer impedance varies with frequency in potential regions where trivial causes such as the dissolution of Cu are not effective. The limiting double layer capacity at high frequency is about 70 μf per apparent sq cm of the surface. Pre-electrolytic purification led to an apparent halving of the transfer coefficient and a considerable increase in exchange current density. The experimentally evaluated coefficients ∂Rdi/∂ω—½ (where Rdi is the diffusional resistance) are about double those theoretically evaluated on the assumption that the true area of the electrode is equal to the apparent area. The values of the experimental coefficients ∂Rdi/∂ω—½ and ∂1/ωCdi/∂ω—½ (where Cdi is the diffusional capacitance) agree well. ∂ lni0/∂ lnaCu++=0.75 when i0 is the exchange current density.
The variation of the double layer capacity with frequency is due to dielectric loss in the water molecules in the double layer. Application of the theory of dielectric loss taking into account the distribution of adsorption energies among the water molecules shows that the observed resistance and capacitance of the double layer in certain Hg-solution and Cu-solution systems can be reproduced with the assumption of relaxation times of about 10—8 and 10—7 sec, respectively. The effect is small on Hg, but much larger on solid metals where the heat of adsorption of water is greater than on Hg. The resistance and capacitance of the double layer on solid metals is intrinsically frequency dependent and this fact (and the existence of a significant double layer resistance) must be taken into account in the evaluation of Faradaic impedance. If the intrinsic frequency dependence of the double layer is taken into account, the Faradaic resistance and the diffusional capacitance behave theoretically; if a frequency-independent double layer impedance is utilized, irrational values of the Faradaic impedance and reaction resistance are obtained.
Diffusion occurs to only about one-fifth of the true surface area.
Calculation of the Energy of Activation for Some Simple Reactions. I. Ortho-Para Hydrogen Reaction
Authors: Lippincott E. R. , Leifer Asa 
Published: January 2005

A model is proposed from which energies of activation and potential energy surfaces of three atom reactions may be calculated. The method makes use of internuclear attractive and repulsive potential functions which have been derived from a quantum mechanical delta-function model. The energy of activation of the ortho-para hydrogen reaction was calculated and found to have a value of 8.5 kcal in agreement with the experimental value. The model predicts the presence of a slightly stable H3 complex. This complex, however, is asymmetric, located at a minimum in the potential curve just before the barrier, and is stable by an energy of about 1 kcal.
The method may be classified as semiempirical. However, all parameters used are obtained theoretically from the proposed model. One advantage of the method is that the main points of interest on the potential energy surface may be calculated without calculating a complete potential energy surface.
Spectroscopic Study of the Monotropic Forms of Monochloracetic Acid
Authors: Barceló José R. , Jorge M. Pilar , Otero Clara 
Published: January 2005

Monochloracetic acid (CClH2–COOH) is a trimorphic substance. Only one of the three forms is stable, viz.: the α form; whereas the β and γ forms are metastable. The infrared spectrum of the forms α and β has been studied; that of the γ form has not been studied because of its extreme instability.
It has been seen that the spectrum of the α form is different from that of the β form. The fundamental frequencies of monochloracetic acid have been assigned, bearing in mind the assignments made by the present authors in another paper for di- and trichloracetic acids.
This assignment makes it possible to determine that the displacements which are observed when passing from form α to β chiefly affect the frequencies bound up with the carboxyl group and more especially those in the OH group. This has been confirmed by the preparation of the deuterated derivatives which likewise present themselves in α and β forms, the same relative differences in frequencies being observed.
It is inferred from this study that the two crystalline forms differ in the structure of the intermolecular dimers (or polymers). The α form is the conventional dimer with two hydrogen bonds. In the β form this intermolecular bond is probably not the double hydrogen bond, since the OH groups show a greater mobility.
Enhancement of Infrared Absorption Bands of Charge Transfer Complexes
Authors: Ferguson E. E. , Matsen F. A. 
Published: January 2005

An enhancement of infrared absorption bands is shown to be inherent in charge-transfer theory due to change in vertical ionization energy or change in vertical electron affinity during the course of molecular vibration. A semiquantitative calculation of the intensity enhancement of the symmetric ring stretching vibrational mode of benzene in the benzene-iodine complex agrees well with the experimentally observed value.
This result shows that previous investigators' assumptions of charge-transfer complex asymmetry, based on observed infrared absorption bands may not be valid.
Electron Spin Resonance in Transition Metal Chelates. II. Copper(II) Bis-Salicylaldehyde-Imine
Authors: Maki A. H. , McGarvey B. R. 
Published: January 2005

The electron spin resonance at 3.2 cm has been observed for single crystals of copper(II) bis-salicylaldehyde-imine diluted to ½ mole percent with the corresponding nickel chelate. Analysis of the spectrum by methods given in the preceding article indicate that the sigma bonding and in-plane II-bonding are appreciably covalent, whereas the out-of-plane π bonding is ionic. Hyperfine interactions in addition to that resulting from the copper nucleus were observed and shown to be attributable to interactions with the nitrogen nuclei adjacent to the copper ion and with the two protons bonded to the carbon atoms directly adjacent to the nitrogen atoms. The two protons bonded directly to the nitrogen atoms do not contribute to the hyperfine interactions. Bonding information obtained from the magnitude of the hyperfine interaction due to the nitrogen nucleus agrees with that obtained from the g tensor and hyperfine interaction of the copper nucleus.
In addition structural information about nickel(II) bis-salicylaldehyde-imine is obtained. The Ni-O distance is 1.92±0.07 A while the Ni-N distance is 1.94±0.05 A. The angle between these bonds is found to be 93±3°.
Free-Radical Stabilization in Condensed Phases
Authors: Golden Sidney 
Published: January 2005

The formation of stabilized free-radical mixtures by the low-temperature condensation of gases containing such species is considered. A primary concern is the amount of free radicals resulting from such a process.
The over-all process of formation of condensed phase stabilized free-radical mixtures involves the original means of their production as gases, the recombination of free radicals as the gaseous mixtures are transported to the seat of condensation, and the recombination which occurs in the immediate vicinity of and within the condensed phase which is formed. For the present purpose only the latter aspect is considered in any detail, the effects of production and prior recombination being summarized in a stated composition for the condensing gas. For simplicity, only mixtures consisting of a single species of atomic free radicals, diatomic molecules which may be formed from their recombination, and inert atomic species are treated.
The basis for stabilization is taken to be isolation. Thus, those condensed phase mixtures are regarded as stable which do not permit free radicals to come in contact with one another. It is assumed, therefore, that condensation occurs at a temperature sufficiently low to render the effect of diffusion negligible. Such recombination which does occur is presumed to do so as a result of the juxtaposition of the atomic free radicals.
Several models of the stabilization process are considered from a statistical viewpoint. In each instance no explicit reference is made to the kinetics of the recombination process. The effects of coordination number, surface condensation versus bulk condensation, condensation coefficient and clustering are treated. In each of the models the dependence of the condensed phase composition upon the gas phase composition and the statistical properties of the constituents is determined.
Theory of Dilute Polymer Solution. II. Osmotic Pressure and Frictional Properties
Authors: Kurata Michio , Yamakawa Hiromi 
Published: January 2005

The osmotic second virial coefficient of flexible polymer solutions is calculated on the basis of the pearl-necklace model with continuous medium approximation. Proper account is taken not only of the intermolecular interaction but also of the intramolecular interaction of segments or the so-called ``excluded volume effect.'' Evaluation is carried out to the triple contact approximation. The results show that the intramolecular interaction has a marked influence on the molecular weight dependence of the coefficient.
Then, theories of the intrinsic viscosity and frictional coefficient are developed on the same model as above, following the Kirkwood and Riseman scheme. The results show that, if α is the linear expansion factor of the polymer coil, the intrinsic viscosity is asymptotically proportional to α2 for the free-draining case and α2.43 for the impermeable case. This implies that even in the limit for impermeable molecule, the hydrodynamic radius of the polymer coil is not proportional to its statistical radius.
Finally a thorough comparison of the present theories with experimental data is made, taking solutions of polystyrene in cyclohexane as an example. The results prove that the theories are very fitted for structural interpretation of experimental data.
Additivity Rules for the Estimation of Molecular Properties. Thermodynamic Properties
Authors: Benson Sidney W. , Buss Jerry H. 
Published: January 2005

A general limiting law is proposed which can be used to systematize the various laws of additivity of molecular properties. This can be stated as follows: ``If φ is a molecular property, then for the disproportionation reaction: RNR+SNS⇄2RNS, Δφ→0 as the separation between R and S becomes large compared to their dimensions.
It is shown that the zero-order approximation is equivalent to the law of additivity of atomic properties, the first-order approximation to the law of additivity of bond properties, the second-order approximation to the law of additivity of group properties, and so forth. It is shown that for Cp and S° (ideal gases), the additivity of atomic properties works to about ±2 cal/mole-°K, while the additivity of bond properties is usually good to about ±1 cal/mole-°K. The latter also estimates ΔHf° to about ±3 kcal/mole. The group additivity relation is generally obeyed to within ±0.5 cal/mole-°K for Cp and S° and about ±0.6 kcal/mole for ΔHf°. Tables are presented for each of the partial properties at 25°C.
The agreements found for the various additivity rules is examined from a molecular point of view and certain extensions and limitations indicated. The application and utility of the rules in estimation of thermodynamic properties is discussed.
The estimation of bond dissociation energies is possible with the additivity rules as are the thermodynamic properties of free radicals. An application of the rules to species NR2 and NS2 show that R and S may be ordered according to their general bond-weakening or bond-strengthening properties. For systems where N is C2H4 it is shown that the first and second bond dissociation energies for RC2H4R is very likely a constant = 59.5 kcal, the excitation energy of C2H4.
Microwave Studies of the Structure of Cyclopropyl Derivatives
Authors: Friend James P. , Dailey B. P. 
Published: January 2005

The microwave spectra of cyclopropyl chloride and cyclopropyl cyanide have been studied and rotational constants for the Cl35 and Cl37 molecules of the chloride and for the normal molecule and two deuterated species of the cyanide have been determined. The two deuterated species are the cis and trans forms of C lim |H2–CHD–C lim |¯H–CN.
For C3H5Cl35, A = 16 625±145 Mc, B = 3905.4±0.3 Mc, and C = 3622.5±0.3 Mc. For C3H5Cl37, A = 16085±415, B = 3810.4±0.5 Mc, and C = 3540.8±0.5 Mc. The following structure fits the rotational constants within the experimental errors: dC–C = 1.5131 A, dC–Cl = 1.7780 A, dC–H = 1.105 A, ≰HCH = 114°36′, ≰HCCl = 120°52.9′.
For C3H5CN, A = 15 917 Mc, B = 3465.06 Mc, and C = 3286.22 Mc. For cis C3H4DCN, A = 14 543 Mc, B = 3419.34 Mc, and C = 3229.15 Mc. For trans C3H4DCN, A = 15 367 Mc, B = 3358.79 Mc, and C = 3161.26 Mc.
The following structure fits the rotational constants B and C to an average of 1.5 Mc: dC–C(ring) = 1.5131 A, dC–C(CN) = 1.4679 A, dC–H = 1.112 A, dC≡N = 1.1574 A, ≰H–C–H = 115°35′, and ≰C(CN)−C−−H=119∘35′.
Analysis of the quadrupole structure in C3H5Cl shows that eqQ along the C–Cl bond axis is —71.7 Mc for Cl35, indicating 23% ionic character. The asymmetry η = 0.156 for Cl35 indicates a double bond character of 4%.
Overhauser Effect in Manganese Solutions in Low Magnetic Fields
Authors: Codrington R. S. , Bloembergen N. 
Published: January 2005

The sign of the Overhauser effect for protons in Mn++ aqueous solutions in external fields between 5 and 20 gauss is such, that the dominant relaxation mechanism is scalar coupling between the protons and electron spins.
The electronic ΔF = 0, ΔmF = ±1 transitions in the hyperfine multiplet were saturated and the enhancement of the proton resonance signal with increasing electronic saturation was observed up to a factor of about 300 times. The dependence of the proton and electron relaxation times on external field agree well with a theory which takes due account of the hyperfine multiplet in the Mn++ ion.
Determination of Molecular Structures from Ground State Rotational Constants
Authors: Costain C. C. 
Published: January 2005

Kraitchman has shown that a single isotopic substitution on an atom is sufficient to determine directly the coordinates of that atom with respect to the principal axes of the original molecule. Kraitchman's formulas represent exact solutions of the equations for the equilibrium moments of inertia. However, the effects of the zero-point vibrations are such that the coordinates obtained by substitution from the ground state moments of inertia I0 are systematically less than r0. These coordinates have here been called r (substitution) or rs, and it is found that rs≃(r0+re)/2, and Is= ∑ imirsi2≃(I0+Ie)/2.
In the usual method of solution, the coordinate of one atom is determined from the equation for I0, and therefore the difference I0—Is must be made up by this one coordinate. This introduces a large error in the structures normally determined from ground state constants, and results in variations of 0.01 A in structures determined from different sets of isotopic species. If instead, we obtain the structure only from the rs coordinates and make no attempt to reproduce the I0 values, the structure is virtually independent of the isotopic species used in the determination. The variation in the structures obtained from different sets of isotopic species appears to depend only on the uncertainties in the rotational constants. In addition, the accuracy is independent of the mass of the substituted atom, and therefore H atoms are located just as accurately as the heavier atoms.
The rs structures of HCN, N2O, OCS, CH3CCH, CH3CN, CH3NC, and the methyl halides have been determined by the isotopic substitution method. For the first three molecules comparisons can be made with equilibrium data, and it is found that the rs bond lengths are no more than 0.002 A greater than the re. The primary interest in the other molecules studied is in the structure of the methyl group. The anomalous separation of the H and D coordinates previously found is readily explained and does not appear in the rs structures. The consistency of the results is such that comparisons between molecules can be made with confidence.
Concerning Reconstructive Transformation and Formation of Glass
Authors: Turnbull David , Cohen Morrel H. 
Published: January 2005

An explanation based on kinetic considerations is developed for the failure of some pure liquids to crystallize. The important parameters are (1) α, the ratio of the molar liquid-solid surface tension to the heat of fusion ΔHf, (2) β, the ratio of the entropy of fusion to R, (3) ΔG′, the kinetic barrier to nucleation, and (4) ΔG″, the kinetic barrier to the growth of the finite crystal. In the absence of foreign nucleating agents sensible crystallization will not occur if αβ⅓≲0.9 and ΔG′≤0, or if ΔG′ or ΔG″≤30(ΔHf/β) = 30 RTm.
In nonreconstructive crystallization the molecules incorporated into the crystal are the same as those existing in the liquid. In this case ΔG′ and ΔG″ are likely to be the same and of the order of magnitude of the free energy of activation for fluid flow, ΔGf. Usually, αβ13∼12 and ΔGf≪30 RTm, in nonreconstructive crystallization and the nucleation of crystals in clean liquids, is sensible at some undercooling. There are some organic liquids in which crystallization is nonreconstructive and that do not crystallize when clean. We have found that the ratio Tb/Tm of the normal boiling point to the melting point is abnormally large in these cases and near two or more for those compounds that clearly form glasses. Since β and ΔG′/RTm are both likely to increase with Tb/Tm, the difficulty of crystallization would increase with this ratio. It is probable that this correlation also holds for inorganic molecular liquids.
In reconstructive crystallization the molecular entities in the crystal differ from those which predominate in the liquid and bonds between atoms must be broken in order for nucleation to occur. Thus ΔG′ can be of the order of the bond energy, which often exceeds 30 RTm, and, excepting in network liquids, much greater than ΔGf.
Bonds between atoms also must be broken for the reconstructive growth of finite crystals. However, this process can be promoted by impurities and molecular fragments in ways not possible in homogeneous nucleation so that ΔG″ as well as ΔGf can be much less than ΔG′. The reconstructive growth of finite crystals at the expense of a different crystal phase can be enhanced similarly so that ΔG″ may be much less than ΔG′ in this case also.
Small-Angle X-Ray Scattering from Solutions of Aerosol OT in Nonaqueous Media
Authors: Siegel L. A. 
Published: January 2005

The small-angle scattering of solutions of di(2-ethylhexyl) sodium sulfosuccinate in n-dodecane has been investigated for the concentration range 6%—75%. The results agree with earlier work of Mattoon and Mathews and of Philippoff, in that a gradual decrease of scattered intensity with angle is found for the low concentrations, while a pronounced intensity maximum at a nonzero angle is found at the higher concentrations. The data further show that there is a gradual transition of the shape of the scattering curve between extremes as the concentration is varied.
It is proposed that the observed changes in shape of the experimental curves represent the transition from gas-type to liquid-type scattering. The x-ray data are consistent with the existence of only one type of micelle over the entire concentration range. It is not necessary to postulate any special intermicellar arrangement to explain the high-concentration scattering maximum.
While no detailed statement as to individual micellar structure can be made with the present data, they are consistent with an inverted structure in which the polar, more heavily scattering ends, are in the interior of the micelle.
It is suggested that the exponential scattering observed in the low-concentration limit may have been overlooked in some earlier investigations of colloidal systems; conclusions drawn in these cases as to inability of the systems to form micelles because of molecular shape may be incorrect.
Theory of Cold Crystallization of High Polymers
Authors: Wunderlich B. 
Published: January 2005

The nonequilibrium limit of random crystallization of linear high polymers is described in this article. Expressions for crystallite size, surface area, crystallinity, and amorphous sequence distribution of crystallizable repeating units in random copolymers after cold crystallization are derived. Melting points and change of crystallinity with temperature in the melting range are discussed. All partially crystallized polymers are found to fall between the two limits of equilibrium and random (or cold) crystallization.
For the system poly(ethylene terephthalate-sebacate) enough data (ΔHu, Tmo, crystal structure, and Cp as a function of temperature and composition) are available, so that the cold crystallization limit could be calculated with help of an IBM 650 electronic calculator.
The Mercury Photosensitized Reaction of Dimethyl Ether
Authors: Marcus R. A. , Darwent B. deB. , Steacie E. W. R. 
Published: January 2005

The mercury photosensitized reaction of dimethyl ether has been investigated at pressures between 28 and 500 mm and at temperatures between 25°C and 292°C. At 25°C the products consist almost entirely of hydrogen and 1,2-dimethoxyethane, and the initial step has been shown to be the abstraction of a hydrogen atom.
At higher temperatures CH2O, CH4, C2H6 and probably CH3OC2H5 become important products. They are derived from the decomposition of the methoxy methyl radical followed by subsequent radical recombination reactions. Carbon monoxide is produced in the later stages from the decomposition of formaldehyde.
By varying the light intensity and pressure it has been shown that ethane and dimethoxyethane are produced by second order recombination of methyl and methoxy methyl radicals respectively. The activation energies of the following reactions have been estimated: CH3+CH3OCH3→CH4+CH3OCH2E=9.0 kcal.  CH3OCH2→CH3+CH2OE=19 kcal.the only assumption being that methyl and methoxy methyl radicals recombine with zero activation energy.