bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dielectric Properties of Polypeptide Solutions. IV. Several Problems on the Electric Dipole Moment of the α-Helix
Authors: Wada Akiyoshi 
Published: January 2005

Relating to the dielectric properties of the α-helical molecule described in a previous report, the following problems have been studied from the standpoint of the confirmed structure of this molecule.
1. The electric dipole moment of the α-helix has been estimated considering the dipole moment in the side chain besides that in the backbone chain.
2. The dielectric constant of the solution of α-helices has been obtained in terms of the dipole moment and polarizability of the solute molecules. The reaction field, which will be induced in such a cylindrical molecule immersed in the dielectric media, has also been examined.
3. It was found that the deviation of the observed dielectric dispersion and absorption curve from Debye's theoretical one of single relaxation time could satisfactorily be explained when the polydispersity of the molecular weight was taken into account.
Kinetics and Mechanism of Ethylene Oxide Decomposition at High Temperatures
Authors: Crocco L. , Glassman I. , Smith I. E. 
Published: January 2005

In a new flow reactor designed for the study of reaction kinetics at high temperatures, the rates of decomposition of ethylene oxide were measured to temperatures approaching its adiabatic decomposition point (∼1200°K). This device is unique in that it follows the reaction process, not by a freezing technique usually employed in flow systems, but by tracing the temperature history of the reaction.
The ethylene oxide decomposition study showed that the kinetics followed an over-all first-order mechanism and the over-all activation energy was 42±2 kcal/mole. The results were found to be independent of the amount of fuel injected, the velocity of the inert carrier gas, and the inert gas itself. A free radical decomposition mechanism consistent with the experimental results is postulated.
Exploratory Study, by Low-Temperature X-Ray Diffraction Techniques, of Diborane and the Products of a Microwave Discharge in Diborane
Authors: Bolz L. H. , Mauer F. A. , Peiser H. S. 
Published: January 2005

It has been suggested that atomic hydrogen may form a loose, one-electron bond with stable electron-deficient molecules such as diborane (B2H6). Such bonding might make possible the stabilization of quasi-atomic hydrogen at higher temperatures or in higher concentrations than have been attained previously. To test this theory, diborane and the products of a microwave discharge in diborane have been studied by x-ray diffraction in the temperature range 4.2° to 100°K.
Two structurally related phases have been distinguished in ordinary diborane. The low temperature or α phase is formed by deposition from the gas at 4.2°K. It transforms slowly to β diborane above 60°K. The β phase is also obtained by depositing at 77°K and annealing above 90°K to eliminate traces of the α phase.
An additional phase is found in specimens formed by freezing at 4.2°K the products of a microwave discharge in diborane. It is probably a boron-hydrogen compound with a triple-point temperature of about 60°K. It may be BH3. This compound is not known definitely, but some evidence for its existence has been reported.
In each experiment with ``discharged'' diborane, warm-up began with a sudden increase in temperature from 4.2° to about 33°K while there was still helium in the Dewar. The source of heat has been traced to hydrogen frozen out with diborane and other products of the microwave discharge. The temperature rise, which may have been initiated by a process such as recombination of atomic hydrogen trapped in the solid, was sustained by heat transferred from the Dewar walls by hydrogen gas released from the sample.
Since the heat release occurred spontaneously at a temperature near 4.2°K it cannot be concluded that diborane helped appreciably to stabilize atomic hydrogen in the solid.
Bond Energies and the Interactions between Next-Nearest Neighbors. I. Saturated Hydrocarbons, Diamond, Sulfanes, S8, and Organic Sulfur Compounds
Authors: Allen Thomas L. 
Published: January 2005

Interaction energies of atoms which are next-nearest neighbors have been determined from thermodynamic data for a number of carbon and sulfur molecules. When these interactions are taken into account, bond energies are found to be constant to a high degree of precision.
Additional factors which have been considered include thermal and zero-point energies, interactions of more distant neighbors, trigonal interactions, and ring strain.Simple equations for the prediction of unknown heats of formation are developed.
Dislocation Type Defects in Glass
Authors: Levengood W. C. , Vong T. S. 
Published: January 2005

Flaws formed on freshly broken surfaces of glass reacted to various types of applied stress in a manner suggestive of dislocation type defects. Localized shear stresses caused existing defects to disappear and created new flaws which formed a cyclic pattern between parallel scratches made on newly created surfaces. These flaws formed behind the scratching tool and appeared to be associated with harmonically moving stress waves in the glass. Thermally induced stress energies were also found to increase the probability of flaw formation.
Matching flaws were produced by nonuniform cohesional forces between internal crack surfaces. This effect was interpreted as the result of limited moisture penetration causing zones of reaction products and localized stress concentrations. The morphology of the defects indicated a dislocation within the glass which produced slip lines on the surface. The critical shear stress found to affect the flaws was determined by loading with spherical indenters.
Molecular Dissociation and Reconstitution on Solids
Authors: Ehrlich Gert 
Published: January 2005

The dependence of heterogeneous reactions on the nature of the solid surface is explored by analyzing the elementary rate processes involved. The relations between the rates of adsorption, surface diffusion, and evaporation, and the depth and distribution of binding sites on the surface are presented. Empirical generalizations concerning the binding energy of adatoms and the cohesive energy of solids are examined; Pauling's additivity rule is found to fail for most metal hydrides and thus does not provide a reliable base for estimating the covalent contribution to the heat of adsorption.
Rates of association of atoms and dissociation of molecules on solids are estimated from a knowledge of the experimental heat of adsorption — ΔH and the postulate that the activated complex for dissociative chemisorption of a diatom has a configuration resembling two noninteracting atoms, one in its equilibrium binding position on the surface, the other in the saddle-point position for surface migration. For chemisorption on clean metals, it is found that an activation energy can be expected only for systems in which the heat of adsorption is small (— ΔH &lt;10 kcal/mole), in agreement with experiment. Conversely, desorption of diatoms by combination of atoms deposited in excess of the equilibrium amounts on metals on which — ΔH &lt;0 is limited only by surface diffusion and therefore should occur rapidly, as is observed.
The mechanism of heterogeneous recombination of atoms is outlined; it is shown that for hydrogen atoms only small variations in the efficiency of this process on different metals are expected at pressures of the monatomic gas less than 10—3 mm, and that these are primarily dictated by the rate of direct recombination between gas phase and adsorbed atoms. For metals on which chemisorption from the molecular gas is endothermic, the recombination coefficient should approach unity above room temperature. In the converse process, the dissociation of diatomic molecules into atoms at a hot metal surface, variations in the rate of atomization may occur for different metals; for those on which adsorption is endothermic the rate should be small since it is the adsorption step which results in specificity. The rate of atomization is also shown to depend upon the first power of the pressure of the molecular gas p2 in the region of low pressures, changing to a dependence on p2½ at higher pressures where encounters between adsorbed atoms become limiting.
The same picture of the activated complex for chemisorption is applied to the interaction of gases with nonmetals. From the appreciable activation energy observed for adsorption of diatoms on nonmetals, it is concluded that binding sites on these surfaces are widely separated. This suggests that dissociation or excitation of the gas-phase molecule to a higher vibrational state should increase the rate of adsorption, and conversely that the recombination efficiency of nonmetals for atoms should be small. These expectations are found to be in agreement with experiment.
Infrared Absorption Spectrum of Lithium Hydroxide
Authors: Wickersheim Kenneth A. 
Published: January 2005

The polarized infrared absorption spectrum of crystalline lithium hydroxide in the region between 2500 cm—1 and 8000 cm—1 has been obtained with a grating spectrometer. The spectrum consists in part of a strong band at 3678 cm—1 polarized parallel to the c axis and bracketed in a nearly symmetric manner by five pairs of side bands polarized perpendicular to the c axis and by two pairs of side bands polarized parallel to the c axis. In addition an isolated band at 7172 cm—1 is observed polarized parallel to the c axis. Changes in the spectrum as the sample temperature is increased from room temperature to 400°C are described.
The hydrogen positions in lithium hydroxide have been deduced. It is shown, using the factor group selection rules as a guide, that the spectrum can be explained as consisting of an infrared active OH stretching fundamental surrounded by binary combinations of lattice fundamentals with the infrared and Raman OH fundamentals. The band at 7172 cm—1 is assigned as the binary combination of the two OH fundamentals. The vibrational modes of the crystal belonging to irreducible representations of the factor group have been constructed to within a good approximation. Tentative assignments of deduced lattice frequencies to constructed modes are presented. The present explanation of the lithium hydroxide spectrum is contrasted with the rotation-vibration explanation of Hexter.
Microwave Spectrum, Internal Barrier, Structure, Conformation, and Dipole Moment of Acetyl Fluoride
Authors: Pierce Louis , Krisher Lawrence C. 
Published: January 2005

The microwave spectra of eight isotopic species of acetyl fluoride are reported. Interaction of internal and over-all rotation splits the rotational lines into doublets. From the doublet separations of CH3COF the height of the threefold (sinusoidal) barrier to internal rotation was calculated to be 1041 cal/mole. Splittings in the spectra of C13H3COF, CH3CO18F, and CD3COF gave barriers of 1041, 1055, and 1031 cal/mole, respectively.
With the assumption of a symmetrical methyl group, the following structural parameters were determined from the observed rotational constants: C–C1.503 ACCF110∘18′C–F1.348CCO128∘21′C–O1.181HCH109∘30′C–H1.084If the requirement of methyl group symmetry is dropped, the best fit to all the data is obtained with the following methyl group parameters: In−plane hydrogenOut−of−plane hydrogensC–H1.082 A1.096 ACCH110∘24′108∘48′HCH110∘51′107∘16′The observed rotational constants of CH2DCOF and CHD2COF were found to require the H(in-plane)-F trans-equilibrium conformation.
From Stark effect measurements on CH3COF and CH3CO18F the dipole moment was calculated to be 2.96 D. The dipole moment makes an angle of 9°30′ with the C–C bond axis and is directed toward the oxygen atom.
Microwave Spectrum of Acetyl Cyanide
Authors: Krisher Lawrence C. , Wilson E. Bright 
Published: January 2005

The microwave spectra of eight isotopic species of acetyl cyanide have been investigated in the region 8000 to 34 000 Mc. The hindered internal rotation of the methyl group splits some of the rotational lines into doublets. Analysis of these splittings for four isotopic species gives a barrier to internal rotation of 1270±30 cal/mole.
From the rotational constants of CH3COCN, C13H3COCN, CH3COC13N, CH3CO18CN, CD3COCN, and CD3C13OCN the following structural parameters were determined: C–H1.086±0.005 A∠HCH108∘44′±30′C=O1.226±0.005∠CmethylCO124∘3′±1∘C≡N1.164±0.005∠CCC114∘59′±1∘Cmethyl–Ccarbonyl1.490±0.010∠CCN180∘ (assumed)Ccarbonyl–Ccyanide1.466±0.010.A study of CH2DCOCN and CHD2COCN shows that in its equilibrium configuration, the acetyl cyanide molecule has a methyl hydrogen opposite the oxygen atom.
A dipole moment of 3.45D was obtained from Stark effect measurements.
Activity Concept in Radiation Chemistry
Authors: Mahlman H. A. 
Published: January 2005

The decomposition of aqueous solutions by ionizing radiations has been interpreted by assuming an initial solvent decomposition into H atoms and OH radicals. Radical recombination gives rise to the observed molecular products H2 and H2O2. Substantiating this hypothesis, it has been demonstrated that reaction of solutes with the radicals depress the yields of the molecular products. The linear dependence of the molecular yields on the cube root of the solute molarity applies very well for dilute solutions of strong electrolytes, i.e., where the molarity and the activity are essentially equal; however, in more concentrated solutions considerable deviation is observed. It is in this region that the activity of an electrolyte manifests itself, and therefore the cube root of the activity is the criterion rather than the molarity.
For this study particular attention was addressed to the depression of hydrogen yields by aqueous sodium nitrate solutions. Alteration of the molecular hydrogen yield was demonstrated by varying the scavenging solute concentration and the activity of the scavenging solute. The addition of three different salts representing uni-univalent, di-univalent, and tri-univalent electrolytes was used to alter the ionic strength of the solutions.
Hydrates of the Tetra n-butyl and Tetra i-amyl Quaternary Ammonium Salts
Authors: McMullan Richard , Jeffrey G. A. 
Published: January 2005

The compounds [(n−C4H9)4N+]nXn−·nyH2O have been prepared where X is F-, Cl-, Br-, CH3CO2-, CrO42-, WO42-, C2O42-, HCO3-, HPO42-, and y is approximately 32. They form an isomorphous crystal series which is tetragonal with a=23.65±0.15 A, c=12.40±0.15 A.
A similar series of the type [(i−C5H11)4N+]nXn−⋅ny′H2O has been prepared where X is F-, Cl-, CrO42-, WO42-, and y′ is approximately 40. They also form an isomorphous group which is orthorhombic with a=12.10±0.10 A, b=21.50±0.15 A, c=12.65±0.15 A.
These compounds are believed to be of the clathrate type, similar in general character to the gas hydrates.
Electrical Conductivity of Single Crystals of MgO
Authors: Mitoff S. P. 
Published: January 2005

The electrical conductivity of magnesium oxide at temperatures in the region of 1300°C is observed to depend upon the partial pressure of oxygen surrounding the sample. The conductivity increases at oxygen pressures both higher and lower than 10—5 atmospheres. At this pressure the conductivity is a minimum. This effect is increased as the iron content is increased and is almost absent in the purest samples.
The conductivity is electronic rather than ionic and the number of charge carriers is controlled by the number of lattice vacancies. The dependence of conductivity on oxygen pressure may be satisfactorily explained by changes in stoichiometry and thus lattice defects in magnesium oxide. These changes in stoichiometry are larger when the magnesium oxide is contaminated with a variable valence impurity like iron than when it is pure.
If an explanation based on iron changing valance state is accepted, then it may be demonstrated by an analysis of the chemical equilibria involved that anion deficiencies must appear at low oxygen pressures, cation deficiences at high oxygen pressures, and that all defects must lie close to the variable valence impurity ions.
C13 Splittings in Proton Magnetic Resonance Spectra. II. Bonding in Substituted Methanes
Authors: Muller Norbert , Pritchard Donald E. 
Published: January 2005

We have measured indirect spin-spin couplings between protons and C13 nuclei in a variety of substituted methanes. As found earlier for hydrocarbons, the coupling constants, JC–H, appear to be linearly related both to the percent s character of the carbon atomic orbital participating in the C–H bond and to the bond length. On the basis of the large variations of the JC–H values and of the C–H bond lengths in these compounds we conclude that the state of hybridization of the carbon atom cannot be reliably inferred from the observed, essentially tetrahedral valence angles. This means that the bonds must in many cases be considered as somewhat bent.
We investigated the dependence of the C–H bond hybridization in compounds of type CH3X upon the properties of the substituent group. The results can be correlated on the assumption that the effective electronegativity and the size of the atom directly attached to the methyl carbon primarily determine the hybridization.
Electron Affinities of Some Halogen Molecules and the Charge-Transfer Frequency
Authors: Person Willis B. 
Published: January 2005

In an attempt to fix the value of the vertical electron affinity of the iodine molecule EI2v the potential curve for I2— has been constructed from semiempirical considerations. From this curve the value of EI2v is estimated to be 1.7±0.5 eV, in apparent contradiction to the value around 0 eV indicated by the electron-capture experiments. It is suggested that the electron-capture experiment may measure the vertical energy for capture to give an excited state of the I2— ion, thus explaining the discrepancy.
Having fixed the value for EI2v, the relationship predicting the charge transfer frequency for iodine complexes is reexamined critically. By fitting curves to the data for three different types of complexes (π donors with I2, amine donors with I2, and complexes with I atoms), three sets of empirical constants required to force the fit are determined. An attempt is then made to calculate these sets of constants from a priori considerations. The success of this treatment supports the general theory, indicating especially that no major terms have been omitted from the estimation of the energy difference, W1—W0. Furthermore, the general argument supports the value of EI2v obtained in the earlier part of the paper as well as the reliability of the estimation of the other parameters. The analysis supports the perpendicular model for the geometry of the complexes between I2 and π donors.
Finally, similar analyses are presented for other halogens; Br2, Cl2, and ICl. Estimates of the vertical electron affinity for these halogens from the empirical potential curves agree reasonably well with estimates from the charge transfer frequency, in support of the results for I2.
Viscosity of Nitrogen, Helium, Neon, and Argon from —78.5° to 100°C below 200 Atmospheres
Authors: Flynn G. P. , Hanks R. V. , Lemaire N. A. , Ross J. 
Published: January 2005

A new capillary-flow viscometer has been developed for the measurement of the absolute viscosity of gases as a function of temperature and pressure. In the viscometer a steady flow of gas is maintained through a capillary of known dimensions, and the pressure difference developed across the capillary is measured as a function of the flow rate. From these measurements there are obtained by extrapolation to zero flow rate the absolute viscosity and information on the deviation from Poiseuille flow.
The viscosities of nitrogen, helium, neon, and argon have been determined in this viscometer from —78.5° (—50° for helium and neon) to 100°C and up to 200 atm. The experimental results are believed to be accurate within 0.1%. Agreement with previous results, where available, is generally satisfactory. All the viscosity data for each gas can be represented adequately by the sum of two functions, one dependent on temperature only, the other dependent on density only.
Diffusion Coefficients of the Systems CO–CO and CO–N2
Authors: Amdur I. , Shuler L. M. 
Published: January 2005

Self-diffusion and mutual diffusion coefficients in the range 195° to 373°K have been measured for the isostere systems, CO–CO and CO–N2. The self-diffusion coefficients are consistently higher than the mutual diffusion coefficients, with differences two- to fourfold greater than the experimental error. On the assumption that the classical Chapman—Enskog transport relations are applicable, parameters have been obtained for intermolecular potentials of the Lennard-Jones (12–6) and the exp-six types.
Parameters derived from diffusion measurements have been compared with those obtained from measurements of viscosity, compressibility and crystal properties. It was not possible, for either system, to reproduce both the transport and equilibrium properties with a single set of parameters. It is concluded that the failure may be attributed mainly to the use of average spherically symmetric potentials instead of potentials which are functions of both relative molecular orientation and internuclear separation.
Crystal Structures of KCuCl3 and NH4CuCl3
Authors: Willett Roger D. , Dwiggins Claudius , Kruh R. F. , Rundle R. E. 
Published: January 2005

The crystal structures of the isomorphous garnet-red copper salts, KCuCl3 and NH4CuCl3, have been determined. Each compound contains discrete, planar, Cu2Cl6= dimers. These dimers are stacked above each other along the crystallographic a axis. The cation exhibits a ninefold coordination.
KCuCl3 is antiferromagnetic below 30°K. Both KCuCl3 and NH4CuCl3 are pleochroic with maximum visible absorption when the electric vector is parallel with the Cu–Cu vector of the dimer.
YH3 and YD3: Heat Capacities and Thermodynamic Functions from 15° to 350°K and Infrared Absorption Spectra
Authors: Flotow Howard E. , Osborne Darrell W. , Otto Klaus , Abraham Bernard M. 
Published: January 2005

The heat capacities of YH3 and YD3 were determined in an adiabatic calorimeter from 15° to 350°K. The heat capacity, entropy, enthalpy, and Gibbs free-energy function for YH3 at 298.15°K are 10.363±0.021 cal deg—1 mole—1, 10.019±0.020 cal deg—1 mole—1, 1613.3±3.2 cal mole—1, and —4.608±0.009 cal deg—1 mole—1, respectively. The corresponding quantities for YD3 are 13.727±0.028, 12.028±0.024, 2024.8±4.0, and —5.237±0.010.
The infrared absorption spectra of YH3 and YD3 were taken in the range 400 to 4000 cm—1. Maxima in the absorption bands of YH3 were observed at 1295, 920, and 640 cm—1 and in the absorption bands of YD3 at 1295/√2, 920/√2, and 640/√2 cm—1. A reasonable assignment of these frequencies to Y—H and Y—D vibrations satisfactorily accounts for the difference between the heat capacities of YH3 and YD3 in the temperature range 50° to 350°K. The lattice parameters as determined by x-ray diffraction for the hexagonal close-packed trihydrides were a0 = 3.672±0.002 Å and c0 = 6.625±0.018 Å for YH3 and a0 = 3.659±0.002 Å and c0 = 6.586±0.019 Å for YD3.