bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Electron Diffraction Investigation of the Structures of Neopentyl Chloride and Silico-Neopentyl Chloride: The Determination of Intensities through the Use of a Rotating Sector
Authors: Hastings J. M. , Bauer S. H. 
Published: January 2005

Constructional details and operational data on an electron diffraction apparatus, in which a rotating sector has been incorporated, are presented. Its range of application and limitations are listed, and methods for the reduction of microphotometer records are discussed.
Electron diffraction photographs of neopentyl chloride and silico-neopentyl chloride were taken with and without sectors. Their structures were deduced by a combination of the visual and photometric procedures. Attempts were made to estimate quantitatively the equivalent temperature factors for libration about the C–C and Si–C bonds. Best values for the interatomic distances and their possible interpretations are presented in the concluding section.
Ionization and Dissociation by Electron Impact: Cyanogen, Hydrogen Cyanide, and Cyanogen Chloride and the Dissociation Energy of Cyanogen
Authors: Stevenson D. P. 
Published: January 2005

The appearance potentials of CN+ in the mass spectra of HCN and (CN)2 have been remeasured and found to be 19.36±0.2 and 20.31±0.2 ev, respectively. Combination of the appropriate thermochemical data with the difference between these energies yields, D(NC–CN) = 6.88−2E(Z) ev where Z is the state of the CN radical either X2Σ+ or A2Πi, that accompanies CN+ from (CN)2, and E(X2Σ+) = 0.00 ev and E(A2Πi) = 1.13 ev. The appearance potential of Cl+ in the mass spectrum of ClCN has also been measured and found to be 17.81±0.2 ev, which value gives D(NC–CN) = 6.92−2E(Y) when combined with the spectroscopic ionization potential of the chlorine atom and the necessary thermochemical data. Here Y is the state of the CN radical that accompanies Cl+ from ClCN. In order that the two determinations of D(NC–CN) be consistent it is necessary that Y = Z and then the two permissible values of D(NC–CN) are 6.90±0.2 ev (Y = Z = X2Σ+) or 4.64±0.2 ev (Y = Z = A2Πi). These results do not permit a choice between White's determination, 6.3±0.2 ev, and Pauling's estimate, 3.9±0.6 ev, but do serve to eliminate from further consideration the determination by Kistiakowsky and Gershinowitz, 3.3 ev. Neither value is compatible with the 5.2 ev suggested by Glockler. However, electron impact data on ethylene and methylene radical give 5.6 ev as the upper limit to energy of dissociation of ethylene into two methylene radicals, and this can be taken as an upper limit to the dissociation energy of cyanogen, suggesting the lower of the two possible values of D(NC–CN) to be correct. Corresponding to this lower value of D(NC–CN), 4.64±0.2 ev, the dissociation energies of H–CN and Cl–CN are 4.80±0.1 and 3.66±0.1 ev, respectively, and the ionization potential of CN is 14.55±0.2 ev.
The specific intensities of the various ions in the mass spectra of (CN)2, HCN, and ClCN characteristic of 75-volt ionizing electrons are given with reference to that of A+ in the argon mass spectrum.
The Theory of Ionic Solutions
Authors: Mayer Joseph E. 
Published: January 2005

The virial development for the osmotic pressure of a solution may be used, if the potentials of average force of the solute molecules at infinite dilution are known, to compute the deviations from perfect solution behavior. The expression for the logarithm of the activity coefficient can thus be obtained as a sum of coefficients multiplied by powers of the concentration. For an ionic solution, with 1/R2 forces, the series is only conditionally convergent. By summing certain additive terms occurring in the coefficients over all powers of concentration convergence can be attained.
The integrations necessary to obtain terms correct up to and including c32 are performed. The results are given in terms of certain functions which can readily be computed.
Asymmetry of Inner Electron Distributions in Homonuclear Diatomic Molecules
Authors: Reiss Howard , Saltsburg Howard 
Published: January 2005

Disturbances in the distributions of inner shell electrons due to bond formation in homonuclear diatomic molecules have been investigated using a Fermi-Thomas type statistics. In the majority of molecules examined the disturbance seems to penetrate only to the shell directly beneath the valence shell.
Plots of the number of electrons disturbed versus atomic number are periodic, the disturbance being less for the alkali molecules than for the halogens. In any one group, these plots are remarkably linear. This behavior has permitted us to calculate the bond distance in Rb2. It is found to be 4.28A. This value is to be compared with the distance 4.32A between nearest neighbors in the metal.
The Infra-Red and Raman Spectra of Cyclopentane, Cyclopentane-d1, and Cyclopentane-d10
Authors: Miller Foil A. , Inskeep Richard G. 
Published: January 2005

The infra-red and Raman spectra of cyclopentane, cyclopentane-d1, and cyclopentane-d10 have been determined for the purpose of establishing the symmetry of cyclopentane. D5h selection rules are found to hold very well. This does not constitute a rigorous criterion for structure in this case, however, because drastic alteration of the symmetry by substituting groups such as D, OH, CH3, or Cl for a hydrogen atom does not appreciably increase the complexity of the spectra. The data have provided two strong arguments against a D5h structure. (1) An assignment could not be made which simultaneously satisfied the product rule and the expected band contours. (2) The entropy of the vapor demands a low frequency (near 140 cm−1 for the assignment in this paper) if the symmetry is D5h. This is completely incompatible with the heat capacity of the solid.
It is concluded that cyclopentane definitely does not have D5h symmetry. The actual geometry of the molecule is still not known. It is shown that a rigid structure of symmetry Cs, C2, or C1 is consistent with the available data. A decision between this and Kilpatrick, Pitzer, and Spitzer's model with a puckered ring and a pseudorotation in place of one of the genuine normal vibrations cannot be made at this time.
Analogous spectroscopic results for perfluorocyclopentane are mentioned briefly for comparison. This molecule is definitely non-planar.
The method of preparation of the deuterium compounds is given. A Pd-on-charcoal catalyst is described which promises to be useful in other hydrogen-deuterium exchange reactions.
Structural Investigations by Means of Nuclear Magnetism. II. Hindered Rotation in Solids
Authors: Gutowsky H. S. , Pake G. E. 
Published: January 2005

The experimental absorption line widths, for nuclei with spin 1/2, at nuclear magnetic resonance are given as a function of temperature for a number of molecular crystals. Temperatures ranged from 90°K to the melting points of the compounds. In some cases it has been possible to relate observed line structure and transitions in the line width to the existence and frequency of certain types of hindered rotational motion in the solid state. These deductions are based on mathematical considerations of the quantitative effect of such motions on the structure and second moment of an absorption line. It is emphasized that relatively low frequency motion of the order 105 cycles/second suffices to narrow the width of an absorption line from its value in the absence of that motion.
1,2-dichloroethane, 1,1,1-trichloroethane, and perfluoroethane were found to have line-width transitions coinciding with changes in crystal form and anomalies in the heat capacity. In 1,2-dichloroethane and perfluoroethane these transitions correspond to rotational motion about the long axis of the molecule. 1,1,1-trichloroethane has a line-width transition corresponding to this type of motion, but the heat capacity anomaly and change in crystal form coincides with a further small decrease in the line width to that characteristic of the liquid. A number of molecules including acetonitrile, methyl iodide, nitromethane, dimethyl mercury, and ammonia have absorption lines at 90°K corresponding to molecular rotation about the C3 figure axis. Various other data and interpretations are presented for 2,2-dimethyl propane, methanol, ethanol, acetone, methylamine, and the ethyl halides. The possibility of estimating the potential barriers hindering rotation in solids from the line-width transitions is discussed.
Primary Step in the Mercury Photo-Sensitized Decomposition of Propane and of Hydrogen
Authors: Masson C. R. , Steacie E. W. R. 
Published: January 2005

An attempt has been made to obtain resonance emission of HgH bands in propane-mercury mixtures illuminated with λ2537. It is concluded that if HgH is formed in the primary step in the photo-sensitized decomposition of paraffins, it must possess excess energy and largely dissociate immediately.
Further experiments with mercury-hydrogen mixtures illuminated with λ2537 have also been made, and the mechanism of the production of excited HgH molecules is discussed.
Rotation-Vibration Spectra of Diatomic and Simple Polyatomic Molecules with Long Absorbing Paths III. The Spectrum of Cyclopropane (C3H6) from 2.3 to 0.6μ
Authors: Sinha S. P. 
Published: January 2005

The absorption spectrum of cyclopropane has been investigated under high resolution (21-ft. grating) in the photographic infra-red and under low resolution (with a photoelectric infra-red spectrometer) in the region 1.2 to 2.3μ with absorbing paths up to 1760 meters. A large number of overtone and combination bands, about 150, have been found. Provisional vibrational assignments of nearly all the strong bands from 2.3 to 1.3μ are given. For the weaker bands no unique assignments are possible.
The parallel band at 10970A has been resolved and its rotational structure has been analyzed. The moment of inertia in the lower state is found to have the value IB=42.15×10−40 g cm2.
The Absorption Spectrum and the Dissociation of H2O2
Authors: Edse Rudolph 
Published: January 2005

Although Holt, McLane, and Oldenberg state that they were unable to observe a sharp cut in the absorption spectrum of hydrogen peroxide vapor, it is shown that their measurements indicate a rather abrupt increase of the absorption coefficient at 1920A.
It is doubtful that the dissociation energy of hydrogen peroxide can be derived from its absorption spectrum. However, it seems possible that the photo-chemical decomposition of hydrogen peroxide gives an upper limit for its dissociation energy.
Our measurements of the absorption coefficient of hydrogen peroxide agree well with the results of Holt, McLane, and Oldenberg.
Some Studies in Molecular Orbital Theory III. Substitution in Aromatic and Heteroaromatic Systems
Authors: Longuet-Higgins H. C. 
Published: January 2005

It is shown that LCAO molecular orbital theory, when combined with first-order perturbation theory, provides a very simple procedure for estimating how far electronic effects will modify the transition state energies for substitution reactions in alternant molecules. This procedure is shown to lead to the same qualitative predictions as resonance theory, but has the advantage that it gives at the same time quantitative information as to the relative effects of substitution at different points in a complex system. The theoretical results agree well with experiment as far as can be ascertained at present.
The approximations involved, and their relation to those of resonance theory, are discussed in detail.
Dissociation and Exchange Equilibria of the Tritium Halides
Authors: Bigeleisen Jacob 
Published: January 2005

The ratios of the partition functions of the tritium halides to their respective protium halides have been calculated. These are combined with one another to give the exchange equilibria between the six pairs of tritium and protium halides. The exchange equilibria with water are calculated. From the exchange equilibria between the tritium halides and protium and the free energy of dissociation of the protium halides, the dissociation equilibria of the tritium halides have been calculated.
The experimental data on the dissociation of HI are reviewed and it is shown that the data of Taylor and Crist on DI and HI are self-consistent as well as in good agreement with theory. The heat of formation of HI at absolute zero, ΔH00, is found to be − 1007±10 calories per mole.
The Absorption Spectra of Manganese Fluoride, Zinc Fluoride, and Manganese-Activated Zinc Fluoride
Authors: Parkinson W. W. , Williams Ferd E. 
Published: January 2005

Thin films of MnF2, ZnF2, and ZnF2:Mn have been prepared by evaporation, and their optical absorption spectra have been measured from 1500 to 2600A. The absorption coefficient of MnF2 has a maximum of 8.64×104 cm−1 at 1613A, corresponding to an oscillator strength of 0.042; while there appears to be a maximum of lower value at 1470A for ZnF2. An unresolved weaker band at 2050A is also evident for MnF2. For the phosphor, ZnF2:Mn, the absorption coefficient is intermediate between those of ZnF2 and MnF2, but the peak characteristic of the Mn++ activator is shifted to 1666A and the oscillator strength of the transition is increased to 1.2.
The relative excitation spectrum of ZnF2:Mn was determined, and maximum response occurred between 1600 and 1670A, indicating that radiation in the strong absorption band characteristic of the activator is most effective in exciting luminescence. Less efficient excitation occurs to 2200A.
It is concluded that a transition to an excited atomic state of the activator, rather than an electron transfer process, is responsible for the first absorption peaks in MnF2 and ZnF2:Mn.
Surfaces of Solids XIX. Molecular Interaction between Metals and Hydrocarbons
Authors: Harkins William D. , Loeser E. H. 
Published: January 2005

The energy of interaction between a hydrocarbon and a metal increases rapidly in the order copper, silver, lead, and iron (Fig. 8), and with the value of P/P0. Tables Ia and Ib give the values of the energy at p/p0=1; i.e., at saturation of the vapor. The values of the work of adhesion WA at 25°C for the clean metals are copper 69, silver 77, lead 89, iron 93. For the oxide coated metals the values are only slightly higher (Table Ib). These increase with decrease of temperature. For n-hexane they are essentially the same at 0°C as for n-heptane at 25°C. Isotherms for n-heptane are given for both 25°C and 15°C. Figure 7 illustrates a common phenomenon: a first-order change at 0.02-mm Hg on clean silver.
The method in general use for calculation of the work of adhesion from the adhesion tension is absurd, since for the usual case in which the liquid wets the solid the work of adhesion is given as twice the free surface energy of the liquid. Thus this states that the nature of the solid has nothing to do with the work of adhesion. Unfortunately, all of the books on surface chemistry give this entirely fallacious method of calculation. On this account it is recommended that the use of adhesion tension should be abandoned, since it is one of the most prolific sources of error in Surface Science.
The Asymmetric Rotor. VIII. The Hydrogen Sulfide Band at 6300 Cm−1
Authors: Allen Harry C. , Cross Paul C. , Wilson M. K. 
Published: January 2005

The absorption spectrum of hydrogen sulfide in the region 6140 to 6420 cm−1 has been measured and the rotational fine structure analyzed through the use of published energy tables for the rigid rotor and a classical correction for centrifugal distortion. The excited state constants giving the best fit are A* = 10.39, B* = 8.90, and C* = 4.55 cm−1. The band center is located at 6289.5 cm−1.
The value of IC—IA—IB and the strong Q branch, indicating the non-vanishing electric moment derivative to be along the least inertial axis, show the upper vibrational level to be the (111) state.
Markoff Chains and Excluded Volume Effect in Polymer Chains
Authors: Montroll Elliott W. 
Published: January 2005

In most of the theoretical work on statistical properties of polymer chains one includes (for mathematical simplicity) configurations which correspond to several monomers located at the same point. Here a mathematical method based on the theory of Markoff chains is used to eliminate short-range excluded volume effects in polymer chains formed on space lattices. Those aspects of the theory of Markoff chains which are important in this problem are briefly reviewed.
If as(s=j—k) is the correlation coefficient between the x component of the position of the jth monomer and that of the kth, then the root-mean-square distance between ends of a chain of degree of polymerization N is proportional to N½ (as N→∞) provided that as→0 more rapidly than A/s1+ε (as s→∞). Here A is a constant and ε is an arbitrarily small positive constant. This condition is satisfied in a chain in which any group of n0 successive monomers do not overlap each other or any monomers in neighboring groups of n0 provided n0≪N.
A detailed analysis of a polymer chain on a square lattice is given.
Self-Quenching and Sensitization of Fluorescence of Chlorophyll Solutions
Authors: Watson W. F. , Livingston Robert 
Published: January 2005

The intensity of fluorescence of solutions of chlorophyll (either a or b) is sensibly independent of concentration, for values less than 2×10−3m. At higher concentrations, the fluorescence decreases with increasing concentration, conforming to the empirical equation, If,max/If=1+4300m2. The absorption spectrum of chlorophyll a is the same at 0.02m as it is for very dilute solutions. These results, as well as the observed temperature coefficient of the fluorescent intensity, indicate that the self-quenching of chlorophyll solutions is not due to the formation of non-fluorescent dimers nor to collisions of the second kind, but is very probably related to the resonance exchange of excitation (16, 17) between an excited and normal chlorophyll molecule.
Measurements of the fluorescence intensity of solutions containing mixtures of chlorophylls a and b indicate that chlorophyll b can sensitize the fluorescence of chlorophyll a, and that the fluorescence of chlorophyll b is more strongly quenched by a than it is by itself.
Statistical Mechanics of Dilute Polymer Solutions. II
Authors: Flory P. J. , Krigbaum W. R. 
Published: January 2005

New thermodynamic relationships applicable to dilute solutions of heterogeneous high polymers are derived. The function previously given to express the interaction between two polymer molecules of equal size is modified to include chemically similar polymer molecules differing in size. With the aid of this more general pair partition function the mutually excluded volume for a pair of polymer molecules is easily computed. The osmotic pressure for a dilute solution of a heterogeneous polymer may be expressed in virial form through the application of conventional methods for treating imperfect gases. The second virial coefficient in the series expansion for the osmotic pressure is readily obtained but it is necessary to resort to the hard sphere approximation for estimation of the third coefficient. The third coefficient is much larger than was indicated by earlier theories now known to be inapplicable to dilute solutions, and plots of π/c vs. c must be appreciably curved if the slope is great. Similar expressions are derived for Hc/τ obtained from light scattering measurements.
For a dilute solution of a homogeneous polymer the value of the second coefficient in either the osmotic pressure or light scattering expression is not entirely independent of molecular weight, as predicted by earlier theories. The effect of heterogeneity on the second coefficient in these expressions is investigated for the special case of a dilute solution of two polymers differing only in molecular weight, from which it follows that the ratio of the second coefficients in the light scattering and osmotic pressure relations may be either equal to two, or greater or less than that value, depending on the heterogeneity ratio.
At the critical miscibility temperature Θ, the excluded volume vanishes and the present treatment becomes identical with previous theories. The latter should be valid for all concentrations only at the unique temperature T=Θ. The primary parameters κ1 and ψ1 governing the heat and entropy of interaction between polymer segments and solvent molecules are difficult to evaluate solely from thermodynamic measurements on dilute solutions except at T=Θ.
The Recombination of Iodine Atoms in Solution
Authors: Noyes Richard M. 
Published: January 2005

A simple theory involving jumps between lattice sites has been used to treat the recombination of atoms produced in solution by photo-chemical dissociation. The results have been applied to experimental data obtained previously on the photo-dissociation of iodine in hexane at 25°C.
The treatment indicates that if a pair of atoms is separated by one molecular diameter in the dissociation process, then the probability is 0.40 to 0.50 that these atoms will recombine by diffusion in a period of 10−6 second or less. The experimental data for light of 436 mμ indicate that if some of the atoms undergo ``primary recombination'' without escaping from the cage of solvent molecules in which they are formed, then a larger number of atoms must become separated by two or more molecular diameters as a result of the photo-dissociation.
For light of 578 mμ the data and calculations indicate that about 35 percent of the atoms become completely separated and ultimately combine with atoms from other molecules, about 30 percent become separated by a molecular diameter but recombine rapidly by diffusion, and about 35 percent either fail to undergo predissociation or recombine without escaping from the cage of solvent molecules in which they are formed.
On the Mass Spectra of Propanes and Butanes Containing C13
Authors: Stevenson D. P. 
Published: January 2005

A mass spectrometric method of analysis of C13 enriched samples of paraffins, both with respect to the gross concentrations of —C013, —C113, and —C213 species and the concentration of C13 isomeric species is described, with particular reference to samples of propane−1—C13, propane−2—C13, n-butane−1—C13, n-butane−2—C13, i-butane−1—C13, and i-butane−2—C13 prepared in connection with tracer studies of certain paraffin reactions. With respect to the analysis, the necessary a priori assumptions and a posteriori checks of the assumptions are described.
The relative intensities of certain C1 and C2 ion fragments characteristic of the 75-ev mass spectra of propane—C013, propane−1—C113, and propane−2—C113, and certain C1, C2, and C3 ion fragments characteristic of the 75-ev mass spectra of the six similar butanes are tabulated. The isotope effects on the dissociation probabilities of certain states of the propane and butane molecule-ions are discussed in terms of a simple qualitative model.
Of particular interest is the observation that in the states of C3H8+ which dissociate into C1 ion fragments, and the states of i-C4H10+ which dissociate into C1 or C2 ion fragments the carbon atoms become essentially indistinguishable, and the mass spectra of the isomeric C113 compounds become essentially identical as far as the relative intensities of these fragments are concerned.