Showing papers in "Journal of Chemical Physics in 1936"

Viscosity, Plasticity, and Diffusion as Examples of Absolute Reaction Rates

Abstract: Since to form a hole the size of a molecule in a liquid requires almost the same increase in free energy as to vaporize a molecule, the concentration of vapor above the liquid is a measure of such ``molecular'' holes in the liquid. This provides an explanation of the law of rectilinear diameters of Cailletet and Mathias. The theory of reaction rates yields an equation for absolute viscosity applicable to cases involving activation energies where the usual theory of energy transfer does not apply. This equation reduces to a number of the successful empirical equations under the appropriate limiting conditions. The increase of viscosity with shearing stress is explained. The same theory yields an equation for the diffusion coefficient which when combined with the viscosity and applied to the results of Orr and Butler for the diffusion of heavy into light water gives a satisfactory and suggestive interpretation. The usual theories for diffusion coefficients and absolute electrical conductance should be replaced by those developed here when ion and solvent molecule are of about the same size.

The Diamagnetic Anisotropy of Aromatic Molecules

Abstract: Values of the diamagnetic anisotropy of benzene and other aromatic hydrocarbon molecules are calculated on the basis of the assumption that the p_z electrons (one per aromatic carbon atom) are free to move from carbon atom to adjacent carbon atom under the influence of the impressed fields. When combined with the assumed values for the contributions of the other electrons (‐2.0×10^(‐6) for hydrogen, ‐4.5×10^(‐6) for aromatic carbon, ‐6.0×10^(‐6) for aliphatic carbon) these lead to principal diamagnetic susceptibilities of molecules in approximate agreement with the available experimental data. The diamagnetic anisotropy of graphite is also discussed.

On the Theory of Dielectric Polarization

Abstract: The polarization of a nonpolar dielectric in a homogeneous field is investigated from a molecular point of view. A statistical calculation of the average local field in a molecule shows that fluctuations in the induced molecular moment give rise to a deviation from the Lorentz field. As a result, small but significant deviations from the Clausius‐Mosotti formula are to be expected. A series expansion for (e—1)v/3 of the following form is obtained (e−1)v/3=P0[1+(1+γ+σ)P0/v+···], where e is the dielectric constant, v the molal volume and P0 the molecular polarization. The coefficients in the corresponding expansion of the Clausius‐Mosotti formula are all equal to unity. The correction γ, arising from translational fluctuations, is about 0.1 for most substances. The correction σ depends upon the optical anisotropy of the molecule and its shape.

The Vibration‐Rotation Energy Levels of Polyatomic Molecules I. Mathematical Theory of Semirigid Asymmetrical Top Molecules

Abstract: The exact classical kinetic energy for a system of point masses is obtained. From this the correct form for the quantum‐mechanical Hamiltonian operator is derived. If the assumption of small vibrations is applied to this operator, the familiar approximation of a rigid top plus normal coordinate vibrator is obtained. In order to secure better approximations, in which larger amplitudes of vibration are admitted, a perturbation method is introduced which permits the change of moment of inertia with vibration, the coupling of rotation and vibration, and the centrifugal stretching effects to be taken into account. If the stretching terms alone are neglected, it is possible to reduce the secular equation for the rotational energy levels to the Wang form, except that ``effective moments of inertia'' must be used whose magnitude depends on the vibrational quantum state. The relation of these quantities to the equilibrium moments of inertia or to the instantaneous moments of inertia averaged over the vibrational motion is not simple, although the numerical deviation from them may not be great. In addition, for molecules with less than orthorhombic symmetry there is the further possibility that the orientation of the principal axes of inertia will vary with the vibrational quantum number. It is also pointed out that the Wang equation should not fit the data when a nearby vibrational state perturbs the state under examination or when the centrifugal effects are large. A method is indicated whereby the latter terms may in principle be calculated.

The Theoretical Treatment of Chemical Reactions Produced by Ionization Processes Part I. The Ortho‐Para Hydrogen Conversion by Alpha‐Particles

Abstract: The possible individual processes that may occur in a gaseous system under irradiation from alpha‐particles have been examined from the theoretical standpoint. The ionization, clustering and the fate of the ions have been studied. The ortho‐para hydrogen conversion under the influence of alpha‐particles has been chosen as an example with which to illustrate the method of treatment. Recent experimental data by Capron have been analyzed to confirm his conclusion that atomic hydrogen is responsible for the large ratio of molecules converted to ions produced (M/N = (700 to 1000)/1). It is also shown that clustering is unimportant in this case and that the paramagnetism of the ions is of negligible importance in producing the spin‐isomerization. The role of mercury atoms in removing atomic hydrogen from the system is found to be negligible. Removal of atoms by three body collision of two atoms with molecular hydrogen is slow compared with removal at the walls of the reaction vessel. Analysis of this latter pro...

On the Isotope Corrections in Molecular Spectra

Abstract: According to the simple theory of the rigid rotator and harmonic oscillator, the coefficients of J(J+1) and (v+½) in the energy should be inversely proportional to respectively the reduced mass and the square root thereof. Actually various small corrections, important only in compounds containing hydrogen or deuterium, make the mass dependence slightly different, and hence, at least in principle, explain why spectroscopic observations may yield slightly incorrect mass ratios for isotopes. The corrections are due to four causes (a) anharmonicity, (b) interaction between vibration and electronic motion even when perturbations between different electronic states are neglected, (c) L uncoupling or in other words perturbations between states differing by one unit in Λ, (d) interaction between states of equal Λ. The formulas for the various corrections are collected—some old, some new or more exact than previously. The relative magnitudes of the different effects are estimated. Incidentally, perturbations between states of equal Λ are studied in general. They should increase in intensity with the vibrational quantum number v, all other things being equal, in contrast to the perturbations due to L uncoupling, which increase with J. The electronic isotope shift, or displacement in the absolute value of the energy is also treated. Here the correction for the motion of the center of gravity of the molecule, usually neglected, is shown to be fully coordinate in importance with other terms. Shifts for ultraviolet lines of hydrogen are calculated with the Wang wave functions, and agree qualitatively with experiment. A concluding section is included on the mean square angular momentum of H2, which enters in connection with diamagnetism and the Stern‐Gerlach effect.

A Study of the Franck‐Condon Principle

Abstract: The validity of the Franck‐Condon principle has been investigated in connection with its application to the calculation of spectral intensities in the continuous radiation due to the transitions between the 1sσ2sσ 3Σg and the 1sσ2pσ 3Σu states of H2. For the latter state, a potential curve was constructed on the basis of the authors' theoretical calculations. For the former state, a curve was computed from spectral data by Dunham's method. Accurate wave functions for both states were determined by mechanical integration with the differential analyzer. Transition probabilities from the first four vibrational levels of the stable state were determined by mechanical integration, both for the case that the electric moment matrix element is constant (as assumed in the Franck‐Condon method) and for the case that it is a linear function of the nuclear separation. In addition integrals were determined which permitted the calculation of the probability of excitation of the several vibrational levels by electron im...

The Effect of Structure Upon the Reactions of Organic Compounds. Temperature and Solvent Influences

Abstract: The effect of a substituent upon the heat of ionization of an organic acid is far from identical with its effect upon the free energy of ionization In the case of benzoic acid derivatives the entropy of ionization varies with structure in a way which can be predicted from the temperature dependence of the dielectric constant of the solvent, and which is closely correlated with the effect of a change in the dielectric constant of the solvent upon the relative strengths of substituted and unsubstituted acids The behavior of aliphatic acids is more complicated, probably because of their less rigid structure Similar considerations apply to the effect of changes in structure of reactant upon other equilibria and upon reaction rates

The Application of the Three‐Dimensional Patterson Method and the Crystal Structures of Proustite, Ag3AsS3, and Pyrargyrite, Ag3SbS3

Abstract: It is shown that the three‐dimensional Patterson method can be so simplified by the use of the symmetry properties of the crystal under consideration that its use in determining the positions of atoms in crystals is practicable. This method is then used to determine the positions of the heavy atoms in proustite, Ag3AsS3. The positions of the sulfur atoms are found by the use of the covalent atomic radii and assumptions concerning bond directions. The structure so derived is found to be compatible with the observed data. Proustite is found to contain pyramidal AsS3′′′ groups and silver atoms forming two bonds to sulfur in almost opposed directions. Pyrargyrite, Ag3SbS3, is found to have almost the same structure as proustite. The analytical statement of the structures is as follows:— The space group, C3v6 — R3c, is common to both proustite and pyrargyrite. The special positions of C3v6 are (in hexagonal axes) (2a)0,0,Z;0,0,12+Z;(6b)X,Y,Z;Y¯,X−Y,Z;Y−X,X¯,Z;Y¯,X¯,12+Z;X,X−Y,12+Z;Y−X,Y,12+Z; and positions der...

Reactions Involving Hydrogen Molecules and Atoms

Abstract: The criticisms of Coolidge and James of activation energy calculations are discussed. It is pointed out that their criticisms of the original London proposal do not apply to the semi‐empirical method which in its present form has little more than a formal resemblance to the original scheme. Until a satisfactory quantum‐mechanical derivation of the semi‐empirical method is provided, it must depend for acceptance on its usefulness and the fact that it is a reasonable interpolation formula for calculating the energies of polyatomic molecules from diatomic ones. The best surface for three hydrogen atoms is constructed and from it the rates of all the possible hydrogen‐deuterium reactions are calculated by means of the general theory of absolute rates, these rates are found to be in excellent agreement with the experimental values. The transmission coefficient for reactions on this surface is investigated. Diagrams showing the angular dependence of the potential energy for an H and for a Cl atom approaching a hydrogen molecule are given.

The Far Ultraviolet Absorption Spectra and Ionization Potentials of H2O and H2S

Abstract: The absorption spectra of H2O and H2S in the region below 1600A have been found to consist of various electronic series accompanied by comparatively little vibrational structure. The electronic series conform fairly well to Rydberg formulas the limits of which give 12.56±0.02 and 10.42±0.01 volts, respectively, for the ionization potentials of these molecules. The analysis fits in very well with Mulliken's prediction that the bands should be due to the excitation and removal of a nonbonding electron localized near the oxygen or the sulphur atom. A tentative rotational analysis given for some of the bands in H2S indicates that the moments of inertia suffer little change by the excitation. Suggestions with regard to plausible atomic term series related with the molecular series are put forward.

The Far Ultraviolet Absorption Spectra and Ionization Potentials of the Alkyl Halides. Part II

Abstract: The absorption spectra of the ethyl and higher halides have been examined in the region 2000–1000A. It has been found that they are essentially similar to those of the methyl halides. The ionization potentials of ethyl iodide are given as 9.30 and 9.88 volts and those of ethyl bromide as 10.24 and 10.56 volts. The ionization potentials of the higher halides cannot be determined exactly because of the presence of continuous absorption from the C–C and C–H bonds, and of the diffuseness of the bands themselves. However there is strong evidence that the ionization potentials of consecutive members of the homologous series diminish asymptotically to a limiting value, the diminution from methyl to ethyl being by far the greatest. A comparison of the way the ionization potentials diminish and the dipole moments of the carbon‐halogen bonds increase as we ascend the homologous series indicates a definite connection between the two phenomena.

Raman Spectra of Amino Acids and Related Compounds I. The Ionization of the Carboxyl Group

Abstract: Raman spectra have been determined for four amino acids and their hydrochlorides; for three fatty acids and chloracetic acid, and their sodium salts; and for several related compounds. The influence of the solvent water on the Raman spectra of aqueous solutions is discussed. The ``carbonyl'' frequency, lying near 1670 cm—1 in the pure fatty acids, shifts to 1720 cm—1 when they are dissolved in water. No shift is found for the corresponding frequency in methyl acetate or acetone. The presence of a charged NH3+ group on the carbon α to the carboxyl increases this frequency by about 20 cm—1. On ionization of the carboxyl group it is found that: (1) The ``carbonyl'' frequency vanishes in all cases investigated. The behavior of the amino acids in this respect is entirely consistent with their structure as zwitterions. (2) A group of lines in the region 1200–1420 cm—1 undergoes characteristic changes in position and intensity. (3) In most cases there is a powerful line in the region 750–930 cm—1 whose frequency increases by 20–40 cm—1 on ionization. The frequency of this line is decreased by about 50 cm—1 for each additional methyl group on the carbon atom adjoining the carboxyl. (4) Ionization markedly decreases the C–H frequency in formic acid, and also certain strong frequencies in methyl and ethyl amine.

I. Calculation of Energy of H3 Molecule

Abstract: The potential energies for linear symmetrical configurations of the triatomic hydrogen molecule have been calculated by the variational method with hydrogen‐like 1s atomic orbitals by varying the ``effective charge'' and the amount of all polar and homopolar states in the eigen‐function. The lowest energies (in kcal./mole = 1/23.06 ev) and corresponding separations between neighboring atoms (in Bohr radii) are given in the table. The activation energies are for the reaction H+H2→H2+H, and are calculated with the same type of approximation for H2 and H3. All of the difficult three‐center integrals for the repulsions between pairs of electrons were calculated explicitly in ellipsoidal coordinates without the use of infinite series. Heithler−LondonH.L. plus PolarWangWang plus PolarExperimentEH3−3EH−53.11−60.39−56.16−67.09−103.rH32.002.001.891.84Act. Energy19.0713.6330.6825.157.

Relation of the States of the Carbon Atom to Its Valence in Methane

Abstract: An extended Heitler‐London‐Pauling‐Slater calculation is given for methane. In addition to the usual quadrivalent configuration of the carbon atom, divalent and other configurations with which it may ``resonate'' are considered, in order to ascertain whether or not s2p2 carbon plays a more important part than usually is supposed. The mathematical formulation, an example of the use of the vector model, leads to a seventh degree secular equation, which is solved for empirical values of the integrals. The influence of resonance upon the energy is found to be small, but not negligible, and increases the stability of the molecule about 1.2 volts over the value for the usual Pauling‐Slater configuration. The state of the carbon atom when it forms four electron‐pair bonds is obtained explicitly in terms of the atomic states, and is found to comprise 5S, 3D and 1D of sp3, together with 3P and 1D of s2p2 and of p4. This, the ``valence state'' of Van Vleck, is 7 volts above the ground state of the carbon atom; resonance lowers it about 2.5 volts. The resonance causes a greater modification in the wave function and in the valence state than it does in the energy. In the final section the relative energies of CH, CH2, CH3 and CH4 are examined under the approximation of electron pairing, and are shown to have the regularly graded values of 4.0, 8.0, 12.1 and 17.0 volts when the experimental values for CH and CH4 are used to determine the unknown integrals. There is no indication that CH2 occupies a favored position, and the valence of four for carbon remains understandable in the light of the theory.

The Limiting High Temperature Rotational Partition Function of Nonrigid Molecules I. General Theory. II. CH4, C2H6, C3H8, CH(CH3)3, C(CH3)4 and CH3(CH2)2CH3. III. Benzene and Its Eleven Methyl Derivatives

Abstract: I. The method given by Eidinoff and Aston for calculating the limiting high temperature rotational partition function has been further simplified. An important special case, comprising molecules which may be represented by a rigid framework to which symmetrical tops are attached in any position is developed. II. The methods of the preceding part are applied to the series of methyl derivatives of methane, and to the completely nonrigid molecule n‐butane. The calculated entropies at 25°C show the same general variation with chain length and number of branches as has been found experimentally from the third law. III. The entropies of all the isomeric methyl derivatives of benzene are calculated. Comparison with third law values for the liquids is hampered by lack of reliable vapor pressure data and of vibration frequencies, but there are no major discrepancies which must be attributed to either the calculated or the observed entropies.

The Vibration‐Rotation Energy Levels of Polyatomic Molecules II. Perturbations Due to Nearby Vibrational States

Abstract: The use of the Wang secular equation for the interpretation of the rotational structure of a vibration‐rotation band of an asymmetrical top molecule is not justified if either of the vibrational states involved in producing the band is perturbed by another vibrational state of nearly the same energy. The present paper discusses the conditions under which such a perturbation is to be expected and gives the secular equation which should be used instead of the Wang determinant in case the perturbation is important. This equation assumes a somewhat simpler form when applied to orthorhombic molecules, in which case it involves only one parameter in addition to the three moments of inertia.

The Ultraviolet Absorption Spectra of Simple Hydrocarbons III. In Vapor Phase in the Schumann Region

Abstract: Absorption spectra measurements between λ = 2300A and 1500A were made for fourteen ethylenic hydrocarbons, which included four butenes, five pentenes, one hexene, two heptenes and two octenes. A comparative study of these results together with those from the earlier papers in the series has shown the existence of certain general relationships between the absorption spectra of all ethylenic derivatives. The number of alkyl groups bound to the carbon atoms of the C=C bond determines the wave number of the first absorption band; there is a progressive shift toward the visible with increasing number of alkyl groups but the nature of the alkyl group has almost no influence on the position of the first band; where two alkyl groups are bound to the same carbon atom (unsymmetrical substitution) or to different carbon atoms (symmetrical substitution), the wave number of the first band is very slightly different. The first band of these derivatives is tentatively assigned to an electronic excitation corresponding t...

The Far Ultraviolet Absorption Spectrum of N2O

Abstract: The absorption spectrum of nitrous oxide below 2200A has been reinvestigated. Much new material has been found, particularly below 1550A, including some discrete systems of bands, and some continuous regions of absorption. No bands are found below 997A, but only continous absorption down to about 850A, the limit of observation. A Rydberg series was found, converging to an ionization potential of 12.66 volts. Evidence was found for a total of ten electronic states including the members of the Rydberg series. The vibration frequency in the electronic transition around 1500A is 621 cm—1.

The Absolute Rates of Reaction of Hydrogen with the Halogens

Abstract: In this paper we apply the statistical‐mechanical method which has only recently been developed for reaction rates to three new groups of reactions. These are the reactions of I2, Cl and Br with the various kinds of hydrogen molecules. In the first type (I2+H2→2HI) symmetry properties enable one to divide the six internal modes of vibrations for the four coplanar atoms into three sets with one, two and three modes of vibration in each so that in obtaining the frequency nothing greater than a cubic is solved. This treatment of the frequencies will apply to a very broad class of reactions. The potential surfaces probably yield too high a zero‐point energy for the activated state. In spite of this result they give the right relative rates for the various isotopic reactions because mass enters very strongly into what in the past has been thought of as the collision factor. The study of isotopic reactions in conjunction with the new theory of rates gives a detailed knowledge of the potential in the activated state and can be carried much farther than has been done in this preliminary treatment. The treatment has been carried far enough however to show its general applicability to these types of processes.

Predissociation of the Oxygen Molecule

Abstract: In the emission spectrum of the oxygen molecule no bands in the Runge system, 3Σu—→3Σg—, having ν′>2 have ever been observed. The absence of these emission bands as well as evidence of broadened rotation lines in the ν′>2 absorption bands suggests that in the 3Σu— state vibration levels above the second undergo predissociation. Rassetti's observations of the fluorescence spectrum of oxygen as well as recent photochemical results support this conclusion. Although it cannot be said that any one of these lines of evidence provides rigorous proof that the oxygen molecule predissociates, collectively they present a convincing argument for the occurrence of predissociation. Radiationless transition from the 3Σu— state is doubtless to the 3IIu state formed from normal atoms. On the basis of the present interpretation the initial process in the photochemical reactions of oxygen caused by light in the region of Schumann‐Runge band absorption is the formation of normal 3P atoms as a result of the predissociation, r...

The Continuous Absorption Spectrum of Bromine: A New Interpretation

Abstract: The continuous absorption spectrum of bromine was investigated quantitatively at six temperatures from 293°K to 906°K, and the contributions of the vibrational levels v″ = 0 and v″ = 1 to the total continuum were deduced from the variation of the absorption coefficients with temperature Contrary to expectation, the absorption from the level v″ = 1 has three maxima and not two, and the absorption from v″ = 0 has a decided hump on the long wavelength side of the maximum These results can be explained if the bromine continuum is composed of two overlapping continua, the stronger one (A) with its maximum at λ4150, and the weaker (B) with its maximum at λ4950 Although it is possible to assign A to the transition 3Π0+u←1Σg+, and B to 3Π1u←1Σg+, better agreement with the Franck‐Condon principle is obtained if A is assigned to 1Πu←1Σg+, and B to 3Π0+u←1Σg+ The latter interpretation is also correlated with what is known of the chlorine and iodine continua On either assumption, the value of re for 3Π1u of brom

The Crystal Structure of Germanium Disulphide

Abstract: Crystals of GeS2 are orthorhombic. The unit cell contains 24 molecules and has dimensions: a=11.66A, b=22.34A, c=6.86A. Accuracy ½ percent. The space groups is Fdd (C2v19). Eight of the germanium atoms are situated on the twofold axes; all other atoms occupy general positions. The twelve parameters involved have been determined. Every germanium atom is tetrahedrally linked to four sulphur atoms, with an interatomic distance of 2.19A. The angle between the two sulphur bonds is 103°. A three‐dimensional network somewhat similar to the silica networks is formed.

The Heitler-London Repulsive State of Hydrogen

Abstract: A variational method has been used in the study of the 1sσ2pσ 3Σu state of H2. Two independent computations with formally different functions gave, for a nuclear separation of 1.5aH, energies which agreed to within 0.03 ev and functions with a root‐mean‐square fractional difference of about 2 percent. A study of the way in which the computed energies converged to a limit, as the complexity of the varied functions was increased, indicates that the interaction energy of the atoms at this distance is +5.145±0.02 ev. Computations were also made for nuclear separations of 1.6 aH and 1.87 aH. A potential curve passed through points thus determined and approaching the Heitler‐London curve asymptotically for large nuclear separations is believed to be accurate to 0.2 ev for nuclear separations greater than 1.35 aH. This curve is compared with the results of previous computations and the curve constructed by Finkelnburg and Weizel to account for the variation with wave‐length of the excitation potential of the con...

The Effect of Rotational Distortion on the Thermodynamic Properties of Water and Other Polyatomic Molecules

Abstract: The classical mechanical expression for the energy of a non‐vibrating, rotating polyatomic molecule is obtained which includes a correction term arising from the centrifugal distortion of the molecule caused by the rotation. Since the rotational partition function closely approaches the classical phase integral for room temperatures or higher, the latter is used to calculate the effect of centrifugal distortion on the entropy, heat capacity and free energy. The correction terms —ρRT2, 2ρRT and 2ρRT must be added to F, S and Cv, respectively. ρ is a constant characteristic of each molecule. The values of ρ calculated are: H2O, 2.04 10—5; H2S, 1.62 10—5; NH3, 1.45 10—5; CH4, 1.72 10—5; C2H4, 0.79 × 10—5. For water this correction amounts to approximately ½ percent of the heat capacity at the boiling point, or +0.032 entropy unit.

Kinetics of Recombination of Iodine Atoms

Abstract: (1) The equilibrium I2+hv→I+I; I+I→I2 was studied in presence of different foreign gases by means of a sensitive optical arrangement. (2) The equilibrium is a ``heterogeneous'' one at low pressure, the atoms recombining mainly by diffusing to the walls. In this region, the dissociation increases with rising pressure. (3) At higher pressure (about 250 mm in He, 40 mm in CO2, etc.), the recombination becomes homogeneous. The transition is a sharp one, and practically no influence of the walls is observed at pressures above the transition point. (4) In the region of homogeneous recombination, the dissociation is exactly proportional to the square root of light intensity and to the inverse square root of pressure, in accordance with the theoretical formulae for the ``recombination by three‐body collisions,'' I+I+X→I2+X. (5) The velocity constants of these reactions are calculated for different gases X. The values are given in Table IV. The order of increasing efficiency in promoting recombination is He, A, H2, N2, O2, CH4, CO2, C6H6. One double collision I+I in 530 is a recombining one in helium, and one in 50 in carbon dioxide at atmospheric pressure. (6) The efficiency as third body is higher for the di‐ and polyatomic molecules than for the monoatomic ones, and increases with growing molecular size and the intensity of the molecular fields of the colliding particles.

Determination of Molecular Structure by Electron Diffraction

Abstract: (1) An apparatus has been designed and built for the purpose of determining molecular structure by electron diffraction using 6400 volt electrons. (2) The apparatus was checked with carbon tetrachloride whose structure is accurately known, and the interatomic distances in, and configurations of, a number of compounds determined. (3) Ethylene oxide was found to be a three membered ring with a carbon‐carbon distance of 1.56±0.05A, a carbon‐oxygen distance of 1.45±0.05A and a carbon‐hydrogen distance of 1.05±0.07A. (4) Sulfur monochloride was found to have the two chlorine atoms attached to different sulfur atoms, the sulfur‐sulfur distance was found to be 2.04±0.05A, the sulfur‐chlorine distance of 1.98±0.05A and an angle of 105±5° between bonds. (5) In acetaldehyde the carbon‐oxygen distance was found to be 1.20±0.05A, the carbon‐carbon distance 1.51±0.05A and the bond angle 122±5°. (6) Paraldehyde was found to have a puckered ring structure with a carbon‐oxygen distance of 1.41±0.05A, a carbon‐carbon distance of 1.52±0.05A and the tetrahedral angle of 109° between bonds.

Studies on Glass XIII. Glass Formation by a Hydrocarbon Polymer

Abstract: Polyisobutylene, with an average molecular weight of about 4900, is at room temperature a highly viscous liquid. When cooled, it has been found to form a glass, with the same transitions in thermal properties characteristic in the vitrification of substances of low molecular weight. The heat capacity of polyisobutylene has been measured from 118°K to 295°K. It increases by 32 percent between 192°K and 202°K. The thermal expansion coefficient of polyisobutylene has been measured from 160°K to 300°K. It increases by 200 percent between 185°K and 205°K. The mean temperature of transition corresponds to a viscosity of about 1013 poises, in agreement with a rule observed generally for glass‐forming materials. The factors on which the transition temperature depends are discussed.