bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Thermal Stabilization and Sintering of Gold Smoke Deposits
Authors: Harris Louis , Jeffries David , Siegel Benjamin M. 
Published: January 2005

Gold smokes made by evaporation in an inert gas atmosphere are initially in a thermodynamically unstable state. A theory based on diffusion of vacant sites to the surface of the crystallites has been developed to describe the process by which the deposit approaches equilibrium. Measurement at different temperatures of the change of resistance associated with the loss of vacant sites gives a value of 23.5 kcal./g atom for the activation energy of this process.
When heated above 100°C the deposits sinter rapidly and undergo pronounced changes in optical properties. However, a gold smoke deposit can be stabilized, by heat treatment at 70°C, so that sintering proceeds at an appreciably slower rate.
Some Studies in Molecular Orbital Theory I. Resonance Structures and Molecular Orbitals in Unsaturated Hydrocarbons
Authors: Longuet-Higgins H. C. 
Published: January 2005

The predictions of qualitative resonance theory, as to the electronic structures of unsaturated hydrocarbons, are analyzed in terms of LCAO molecular orbital theory. The following results are proved for ``alternant'' hydrocarbons, that is, hydrocarbons containing no odd-membered unsaturated rings:
(1) The number of unpaired electrons present in the ground state is at least as great as the number of carbon atoms having a deficiency of valence bonds in any principal resonance structure.
(2) With a few special exceptions, these odd electrons are distributed over just those atoms which have a deficiency of valence bonds in one or more of the principal resonance structures.
(3) In singly charged hydrocarbon anions or cations the ionic charge is located on just those atoms which bear charges in the various principal resonance structures.
It follows that enumeration of the principal resonance structures of a hydrocarbon molecule or ion gives much valuable information as to its electronic structure; and in particular, an alternant hydrocarbon possessing no normal Kekulé-type structure must have a paramagnetic ground state, and behave as a radical or multiradical.
These results do not depend on the neglect of overlap, or the assumption of a constant carbon-carbon resonance integral.
Hindered Rotation in Methyl Alcohol with Note on Ethyl Alcohol
Authors: Halford J. O. 
Published: January 2005

The potential barrier to the internal rotation in methyl alcohol is recalculated from the entropy with the aid of new molecular dimensions generously provided by Burkhard and Dennison. The barrier calculation is examined for temperature dependence and checked for reliability by recalculation with the Clapeyron equation substituted for parts of the data. The result is 1600±700 cal./mole, which includes the new spectroscopic barrier of Burkhard and Dennison at 326 cm−1. Within the range covered by the result, a residual entropy up to 0.50 cal./mole deg. is possible, and the retention of 0.46 e.u. by the crystal is consistent with a reasonable simple assumption about the distribution of hydrogen bonds.
It is suggested, by analogy, that the barrier to the hydroxyl group rotation in ethyl alcohol should be about 1000 cal./mole.
Molecular Motion in Certain Solid Hydrocarbons
Authors: Andrew E. R. 
Published: January 2005

An investigation has been made of the variation of the nuclear resonance absorption line width with temperature for four long chain aliphatic compounds and eight aromatic hydrocarbons. The aliphatic compounds are dimorphous; in the lower temperature modification it is concluded that the molecules are rigid at the lowest temperatures, but that an increasing number of molecules rotate about their length as the temperature increases; in the upper temperature modification all the molecules rotate. The naphthalene crystal lattice is found to be rigid up to the melting point. Benzene and anthracene, however, show sharp line-width transitions at about 110° and 190°K, respectively. It is suggested that in benzene this is due to tunnelling or rotation of the molecules about their hexagonal axes. The explanation for anthracene is less clear, but it is suggested that each molecule rotates about its long diad axis. The xylenes, mesitylene, and hexamethylbenzene show internal rotation of the CH3 groups at all temperatures above 95°K. In addition, hexamethylbenzene has a line-width transition over the range 135–210°K, attributed to tunnelling or rotation of the molecules about their hexagonal axes.
A calculation is made of the reduction of the intramolecular contribution to the resonance line second moment caused by rotational oscillation of molecules in a crystal lattice. The effects of certain types of molecular motion on the intermolecular contribution are also calculated.
Light Scattering in the Critical Region. I. Ethylene
Authors: Cataldi H. A. , Drickamer H. G. 
Published: January 2005

1. In the neighborhood of the critical point, light scattering reveals the presence of four regions: a. A region where the light scattering depends on the inverse fourth power of the wave-length. b. A region of increasing scattering and decreasing dependence on wave-length, beginning about a degree above the critical temperature, and extending about a degree. The maximum scattering in this region is of the order of 100 times the initial value. c. An abrupt decrease in scattering, accompanied by absorption which sets in at a higher temperature for the shorter wave-length. d. A large and erratic increase in scattering, apparently resulting from condensation.
2. The scattering observed upon cooling and heating are identical, provided the temperature does not drop below the temperature for zero scattering or condensation.
3. The wave-length dependence of light scattering is not completely described by any existing theory.
4. Applying the Ornstein-Zernike equation where it is possible, one calculates clusters of about 20 molecular diameters more than a degree above the critical temperature. These clusters increase rapidly with decreasing temperature.
The Primary Quantum Yield of Dissociation of Iodine in Hexane Solution
Authors: Zimmerman Joseph , Noyes Richard M. 
Published: January 2005

The primary quantum yield for the photo-dissociation of iodine in degassed hexane at 25° has been calculated from measurements of the mean lifetime of the chains involved in the exchange of iodine atoms with trans-diiodoethylene. The primary quantum yield to an accuracy of ±15 percent is 0.59 at 436 mμ and 0.37 at 578 mμ. The deviation of this quantity from unity is affected both by the ``primary recombination'' of atoms which fail to escape from the original ``cage'' of solvent molecules, and by the ``secondary recombination'' of the original atoms by diffusion during a time which is very short compared to that in which either is apt to encounter an atom from another molecule.
The specific rate constant for the recombination of iodine atoms in hexane solutions has been determined and has been shown to be about one fifth of the rate constant for collision in the gas phase.
The presence of air decreases the rate constant for the photochemical exchange of iodine with diodoethylene by a factor of four and increases the apparent mean lifetime of iodine atoms by a factor of one hundred.
The Vibrational Spectra and Structure of Inorganic Molecules. I. The Infra-Red Spectrum of F2O from 2.5 to 25μ
Authors: Bernstein H. J. , Powling J. 
Published: January 2005

The infra-red spectrum of gaseous F2O has been obtained from 2.5 to 25μ at pressures of 10 mm to 600 mm Hg in a 10-cm cell and at 600 mm Hg in a meter cell.
All three fundamentals have been observed and identified.
The fine structure of a ⊥ band was resolved and gave an estimate of the bond distance and apex angle as 1.38±0.03A and 101.5±1.5°, respectively.
The upper and lower limits of the constants of a quadratic potential function with all possible interaction constants have been obtained.
On the Electrical Conductivity of Violanthrone, Iso-Violanthrone, and Pyranthrone
Authors: Akamatu Hideo , Inokuchi Hiroo 
Published: January 2005

Violanthrone, iso-violanthrone, and pyranthrone have electrical conductance to a certain degree. This is due to the molecular structure of these compounds, which are made of the network planes of carbon atoms, and to the assumption that the π-electron contribute to the electrical conduction.
The electrical resistivity of violanthrone, iso-violanthrone, and pyranthrone was measured. The values at 15°C are as follows; 2.3×1010 ohm-cm, 5.7×109 ohm-cm, and 3.9×1015 ohm-cm respectively. The resistivity decreases with increasing temperature in every case, and a good linear relationships is observed between the logarithm of the resistivity and the reciprocal of the temperature. As the activation energy of the electrical conductance, the following values were observed; 0.39 ev, 0.375 ev, and 0.53 ev respectively. The values for violanthrone and iso-violanthrone suggest that they can be assumed to be intrinsic semi-conductors.
Thermal Diffusion in the Critical Region. II
Authors: Giller E. B. , Duffield R. B. , Drickamer H. G. 
Published: January 2005

The previous measurements on thermal diffusion in the critical region for the system ethane-xenon are extended and completed, with the use of a modified radioactive tracer technique. A rough calculation of cluster size in the critical region is made. A mechanism of molecular motion in the dense gas above the critical point, consistent with the data is present. It is shown that the transformation between dense gas and liquid occurs without discontinuity as far as thermal diffusion is concerned.
The thermal diffusion columns operated in the region of turbulent heat transfer gave a separation as predicted by the modified theory of the column.
Thermodynamic Properties of the Internal Rotation in Methyl Alcohol Vapor from 200 to 500°K
Authors: Halford J. O. 
Published: January 2005

At ordinary and lower temperatures the thermodynamic properties of the methyl alcohol internal rotation are beyond the limits of available tabulations. For any internal rotator, of a given symmetry, with a fixed moment of inertia and potential barrier, two limiting values of each property can be calculated for any chosen temperature. Available tables are restricted to those cases for which the differences between the limiting values can be neglected. When, as with methyl alcohol, the differences are large, the representative values can be found by taking proper account of the symmetry and the dependence of the internal rotator energy levels upon the external rotations.
For methyl alcohol, the correct intermediate thermodynamic properties are obtained by using for the partition function and its derivatives the numerical mean of the limiting values of these sums obtained for the general rotator. This simple rule, however, is not necessarily applicable to other compounds.
Heat capacities and entropies, calculated from the spectroscopic potential barrier of 932 cal./mole and other molecular constants, are considered in relation to experimental data.
The Thermodynamics of Some Non-Isothermal Systems
Authors: Tuck L. Dallas 
Published: January 2005

The thermodynamic theory of non-isothermal systems of liquid solutions is treated by the method of Tolman and Fine, which method includes consideration of the irreversible processes in calculating the conditions of the steady state.
The concept entropy of transfer of a dissolved molecule is discussed in terms of the interaction of the molecule with the solution. The method of Tolman and Fine is then applied in the derivations of the Soret ``equilibrium'' and the e.m.f. of a thermocell. It is shown that the irreversible transport of heat down the temperature gradient has no effect upon the steady-state conditions, even for finite values of the gradient.
The C–Br Bond Dissociation Energy in Benzyl Bromide and Allyl Bromide
Authors: Szwarc M. , Ghosh B. N. , Sehon A. H. 
Published: January 2005

The pyrolysis of organic bromides in a stream of toluene is described as a method for the determination of the C–Br bond dissociation energies. The technique used makes it possible to discriminate between two mechanisms of decomposition: R.Br→R·+BrR.Br→olefin+HBr.It was found that both benzyl and allyl bromide decomposed according to mechanism (a), the bromine atoms reacting readily with toluene to give hydrobromic acid. The rate of the primary dissociation process was measured by the rate of formation of HBr. It was proved that the thermal decompositions of benzyl and allyl bromide were homogeneous gas reactions obeying first order kinetics. The activation energies were calculated at 50.5±2 kcal./mole and 47.5±2 kcal./mole, and identified with D(C6H5.CH2–Br) and D(CH2:CH.CH2–Br), respectively.
The fate of the allyl radical is discussed, and a rough estimate of the activation energy for the reaction CH2:CH. CH2·+C6H5. CH3→CH2:CH. CH3+C6H5CH2·leads to a value of 14–17 kcal./mole.
The problem of ionic contribution in the C–Br bonds is discussed.
The estimation of the dissociation energies of the C–Br bonds of various organic bromides is of great interest since the values for these dissociation energies, combined with the heats of formation of the relevant bromides in the gaseous state, make it possible to determine the heats of formation of various organic radicals. Furthermore, the latter data in conjunction with the heats of formation of hydrocarbons enable us to calculate the various C–H and C–C bond dissociation energies and the resonance energies of the relevant radicals.
Infra-Red and Ultraviolet Spectra of Sulphur Monoxide
Authors: Jones A. Vallance 
Published: January 2005

The infra-red spectrum of sulphur monoxide, prepared by the method of Schenk, has been examined between 400 cm−1 and 2000 cm−1. Bands were observed at 679 cm−1 and 1165 cm−1.
The ultraviolet absorption band system discovered by Schenk in the region 3500A to 2500A has been obtained under high resolution (21-ft. grating). A very sharp predissociation occurs at 31,702 cm−1 leading to an upper value for a dissociation limit of 91 kcal. mole−1. A ground state vibration frequency of 679 cm−1 was deduced from a partial analysis of the electronic absorption band system.
It has been shown that the molecule cannot be diatomic SO, but probably has the formula S2O2, as suggested by Kondrat'eva and Kondrat'ev. The spectroscopic evidence supports the structure S=S S=O S=O.
Motions of Molecules in Condensed Systems. VII. The Infra-Red Spectra for Single Crystals of Ammonium Nitrate and Thallous Nitrate in Polarized Radiation
Authors: Newman Roger , Halford Ralph S. 
Published: January 2005

Infra-red spectra in plane polarized light for properly oriented, thin sections from single crystals of NH4NO3 (IV), NH4NO3 (III), and TlNO3 (γ) are described and interpreted. The selection of proper orientations for such work is indicated for crystals in general and potential difficulties with some types are noted.
Spectra for the first two crystals show (1) that absorptions by molecular modes of nitrate ion, and their combinations, are strongly polarized in directions predicted for these structures by the general theory of crystalline spectra; (2) that envelope structure resulting from combinations between molecular modes and lattice modes is present but not uniquely polarized, again in agreement with the general theory; (3) that absorptions by molecular modes of ammonium ion appear to be unpolarized, indicating that these ions are disordered from rotation or other causes.
Spectra for the third substance are used to complete the determination of its crystal structure. One band in this substance has a remarkable envelope consisting of a strongly polarized central branch and, at room temperature, three pairs of symmetrically distributed, virtually unpolarized satellites. The satellites become more numerous at lower temperature (see accompanying article).
The spectra for the several substances suggest that optical branches of their lattice mode distributions are located between about 35 and perhaps 200 cm−1.
The Mass Spectra of C1–C4 Monodeutero Paraffins
Authors: Stevenson D. P. , Wagner C. D. 
Published: January 2005

The magnetically scanned mass spectra of methane-d, ethane-d, propane−1-d, propane−2-d, n-butane−1-d, n-butane−2-d, i-butane−1-d, and i-butane−2-d, characteristic of 75-volt ionizing electrons and 75°C are given and compared with the mass spectra of the corresponding hydrocarbons.
A qualitative account of the origin of the isotope effects in mass spectra is given. It is shown that in a molecule containing equivalent isotopic species, the molecule-ion formed by electron impact will preferentially dissociate the lighter isotope and that the mass spectra of symmetrically substituted isotopic species (A′BA′) will be more like the mass spectra of the isotopically pure species (ABA) than are those of the unsymmetrically substituted isotopic species (ABA′). It is further shown that the equality (or lack thereof) of parent ion sensitivities of different isotopic preparations to the parent ion sensitivity of the natural substance is not a criterion of the purity (or lack thereof) of the preparations. Attention is called to the close relation between isotope effects in mass spectra and temperature effects in mass spectra.
The two-parameter empirical theory of isotope effects proposed by Evans, Bauer, and Beach is applied to the mass spectra of the methanes and ethanes and found to be inadequate for the prediction of mass spectra for accurate analysis of isotopic mixtures. It is found, however, that for certain electron impact induced processes, such as RH+ε−→R++H+2ε−, the effective values of the parameters, Γ and π, are essentially equal for the monodeutero C1 through C4 paraffins.
It is shown that for the process, RH+ε−→R++H+2ε−, the specific dissociation probability of secondary hydrogens is greater than that of primary hydrogens by a factor of 4 for propane and 10 for n-butane, while in isobutane the specific dissociation probability of the tertiary hydrogen is 30 times that of a primary hydrogen.
It is found that in certain states of the paraffin molecule-ions the hydrogens are sufficiently mobile that they undergo very extensive intramolecular redistribution in the short life of the molecule ion (half-life &lt;0.1–1.0 microseconds) before they dissociate. Such states are of less common occurrence among paraffins than among olefins.
Dielectric Constant of Benzene at 25°C by the Wyman Method
Authors: Brown A. S. , Levin P. M. , Abrahamson E. W. 
Published: January 2005

Apparatus and techniques are described for obtaining reliable absolute dielectric constants by the Wyman resonance cell method.
Calcium hydride has been shown to be a drying agent for benzene far more satisfactory than sodium wire, reducing drying time from the six-month period demonstrated in the literature to an interval approximating one day.
At 25°C the values for benzene's dielectric constant were 2.2747±0.0003, but the higher limit is presently preferred. These results fall within the range of the best recent values obtained in other laboratories. The reasons for the discrepancies appear explicable in view of the findings of this investigation.
LCAO Molecular Orbital Computation of Resonance Energies of Benzene and Butadiene, with General Analysis of Theoretical Versus Thermochemical Resonance Energies
Authors: Mulliken Robert S. , Parr Robert G. 
Published: January 2005

The decrease in πx-electron energy for the change from a Kekulé to a proper benzene structure is computed purely theoretically by the method of antisymmetrized products of MO's (molecular orbitals), in LCAO approximation, using Slater 2pπx AO's (atomic orbitals) of effective charge 3.18, and assuming a carbon-carbon distance of 1.39A. The result (73.1 kcal/mole) is a theoretical value for the gross (vertical) resonance energy of benzene taken for constant C–C distances of 1.39A. In order to make a comparison with the net or ordinary empirical resonance energy, several corrections to the latter are required. The principal one is for the ``compression energy'' required to compress the single and stretch the double bonds of the Kekulé structure from normal single and double-bond distances to 1.39A. The others (not hitherto clearly recognized) involve hyperconjugation and related effects. The corrections are discussed and their magnitudes estimated, but a reliable value can be obtained only for the compression energy. Allowing for this alone, the computed net resonance energy is 36.5 kcal. This agrees, within the uncertainties due to the omitted correction terms, with the value (41.8 kcal) of the ``observed'' resonance energy Δ based on thermochemical data.
Here Δ is the departure of the actual heat of formation ΔHf0 of benzene from the value given by a standard formula for nonresonating hydrocarbons. A new standard formula containing corrections for the mutual effects of neighboring carbon-carbon bonds is given; this is of interest also for itself, and its significance is briefly discussed.
The analysis given in the paper serves to clarify hitherto existing obscurities in what is meant by ``resonance energy.'' An analysis of the nature and significance of ``nonresonating'' structures (like for example Kekulé benzene) is also included, using He2, 1,3 butadiene, and benzene as examples. Repulsion terms in the LCAO MO theory occur for nonresonating structures, which appear to be the counterpart of exchange repulsions of the valence-bond theory. When resonance occurs, it more or less overcomes these repulsions.
The gross resonance energies of cis- and trans−1,3-butadiene are computed by the same method. For transbutadiene, the computed value corrected for compression is 3.7 kcal/mole, while the ``observed'' thermochemical value Δ is 6.5.
Sum Rules for the Vibration Frequencies of Isotopic Molecules
Authors: Decius J. C. , Wilson E. Bright 
Published: January 2005

The squares of the frequencies of isotopically related molecules obey certain simple sum rules. Whenever there exists a chemical exchange reaction involving only isotopic variations of a single type of molecule, such that the reaction is balanced at each atomic position of the molecule, then a relation of identical form exists between the sums of the squares of the frequencies. Thus Σν2(H2O)+Σν2(D2O)=2Σν2(HDO)  and  Σν2(N14H3)+Σν2(N15D3)=Σν2(N14D3)+Σν2(N15H3).If, as in the latter example, the molecules all have the same symmetry, the sum rule may be applied separately to each factor of the secular equation. When forms of lower symmetry appear (as in the example involving the water molecule), symmetry factoring may or may not be possible. In such cases it is necessary to employ certain group-theoretical considerations; the possible factoring is not in general identical with that appropriate for the product rule.
Examples of the application of the sum rule are given, involving the acetylene, water, methane, and hydrocyanic acid molecules. The existence of higher order isotope rules, intermediate between the sum and product rules, is pointed out.