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Showing papers in "Journal of Chemical Physics in 1939"


Journal ArticleDOI
TL;DR: In this paper, the theory of phase change is developed with the experimentally supported assumptions that the new phase is nucleated by germ nuclei which already exist in the old phase, and whose number can be altered by previous treatment.
Abstract: The theory of the kinetics of phase change is developed with the experimentally supported assumptions that the new phase is nucleated by germ nuclei which already exist in the old phase, and whose number can be altered by previous treatment. The density of germ nuclei diminishes through activation of some of them to become growth nuclei for grains of the new phase, and ingestion of others by these growing grains. The quantitative relations between the density of germ nuclei, growth nuclei, and transformed volume are derived and expressed in terms of a characteristic time scale for any given substance and process. The geometry and kinetics of a crystal aggregate are studied from this point of view, and it is shown that there is strong evidence of the existence, for any given substance, of an isokinetic range of temperatures and concentrations in which the characteristic kinetics of phase change remains the same. The determination of phase reaction kinetics is shown to depend upon the solution of a functional equation of a certain type. Some of the general properties of temperature‐time and transformation‐time curves, respectively, are described and explained.

9,458 citations


Journal ArticleDOI
TL;DR: In this paper, an extension of the Onsager theory of dielectric polarization is presented, which is applied to liquid water under the assumption of tetrahedral coordination and directed bonds between neighboring molecules.
Abstract: An extension of the Onsager theory of dielectric polarization is presented. The local dielectric constant is approximated by the macroscopic dielectric constant of the fluid in a region outside a molecule and its first shell of neighbors rather than in the entire region exterior to the molecule. In addition to the molecular dipole moment, the average value 〈cosγ〉Av of the cosine of the angle between neighbor dipoles is a determining factor. Hindered relative rotation of neighboring molecules produces a correlation between their orientations and prevents 〈cosγ〉Av from vanishing. The theory is applied to liquid water under the assumption of tetrahedral coordination and directed bonds between neighboring molecules.

1,660 citations


Journal ArticleDOI
TL;DR: In this paper, a method for obtaining the secular equation for the vibration frequencies of a molecule directly in expanded form, i.e. as an algebraic rather than a determinantal equation, is described.
Abstract: A method is described for obtaining the secular equation for the vibration frequencies of a molecule directly in expanded form, i.e. as an algebraic rather than a determinantal equation. The force constants occur literally and the masses may occur either literally or numerically, as desired. The symmetry may be employed as usual to factor the secular equation. Several methods of obtaining approximate roots are described for which the expanded form is particularly suitable. Finally, an example, the nonlinear general triatomic molecule, is worked out algebraically.

651 citations


Journal ArticleDOI
TL;DR: In this article, the free energy of a rigid body is calculated as a function of temperature, and of the six homogeneous strain components, for a regular (cubic) lattice.
Abstract: The Helmholtz free energy, A, of a rigid body is a function of temperature, and of the six homogeneous strain components. If the crystal is to be rigid, three inequalities must be satisfied for the derivatives of A with respect to the six strain components, for a regular (cubic) lattice. This enables one to limit the pressure‐temperature range for which the crystal is stable. The violation of the condition c44>0, that the crystal resist shearing, is interpreted as leading to melting. From a knowledge of the forces between the molecules the phase integral, and therefore the free energy, may be calculated as a function of T, V, and the six strain components. The numerical calculations are carried out for a body‐centered cubic lattice. The product of all the frequencies is calculated directly, so that the assumption that the Debye equation for the frequency distribution holds, is not necessary. The melting curve, pressure against temperature, is then determined.

583 citations


Journal ArticleDOI
TL;DR: In this article, the free energies of hydration of the alkali and halide ions are found to agree reasonably well with the simple expression of Born (ΔF=(1−1/D)Ne2/2re) for solution of charged spheres in a dielectric medium, provided the crystal radii are suitably modified so as to correspond to the radii of the cavities in the dielectrics.
Abstract: The free energies of hydration of the alkali and halide ions are found to agree reasonably well with the simple expression of Born (—ΔF=(1–1/D)Ne2/2re) for solution of charged spheres in a dielectric medium, provided the crystal radii are suitably modified so as to correspond to the radii of the cavities in the dielectric medium. The results show that the dielectric constant of water remains large even in the intense field next to the ion. The entropies of hydration are also found to be consistent with these radii. Because of the simplicity of this calculation, the resulting free energies of solution of individual ions are considered to be a priori the most probable and are used to calculate a value of —0.50 volt for the absolute potential of the calomel half‐cell.

374 citations


Journal ArticleDOI
TL;DR: In this article, the normal coordinate theory for a molecular cluster such as X·6H2O (X=Ti, V, Cr) is examined and the Stark splittings in such fields, quite apart from the Jahn-Teller effect, are obtained as a corollary.
Abstract: The present article develops the mathematical theory needed in connection with the preceding paper, and with a study of paramagnetic relaxation to appear later. Jahn and Teller have shown that the normal coordinate theory for a molecular cluster such as X·6H2O (X=Ti, V, Cr) is materially different from usual if the X ion is degenerate. Namely, it is impossible to eliminate linear terms in the atomic displacements simultaneously from all substates of the degenerate level. Consequently, stability is achieved only if the degeneracy is lifted, and so the water group distorts itself so that it is not cubically arranged. A calculation is made of the magnitude of the effect, which has an important bearing on magnetic behavior. In order to allow for the disturbing effect of distant atoms, the cluster X·6H2O is not treated as free, but rather as embedded in a trigonal field of force. The Stark splittings in such fields, quite apart from the Jahn‐Teller effect, are hence obtained as a corollary.

342 citations


Journal ArticleDOI
TL;DR: In this article, a generalization of a preceding note on the statistical theory of condensation phenomena is presented, based on the idea that the macroscopic transition of a substance from a phase A to a phase B is preceded by the formation of small nuclei of the B phase within A, these nuclei being treated as resulting from ''heterophase'' density fluctuations or as manifestations of a generalized statistical equilibrium in which they play the roles of dissolved particles, whereas the A phase can be considered as the solvent.
Abstract: The present paper is a generalization of a preceding note on the statistical theory of condensation phenomena. It is based on the idea that the macroscopic transition of a substance from a phase A to a phase B is preceded by the formation of small nuclei of the B phase within A, these nuclei being treated as resulting from ``heterophase'' density fluctuations or as manifestations of a generalized statistical equilibrium in which they play the roles of dissolved particles, whereas the A phase can be considered as the solvent. The application of the general theory to premelting phenomena in crystals leads to a quantitative explanation of the abnormal increase of the specific heat of the thermal expansion coefficient (and of the electric conductivity, in the case of ionic substances) in the close neighborhood of the conventional melting point, with the result that the surface tension between a crystal and its melt must be of the order of 1 dyne/cm. This result is checked by a calculation of the temperature corresponding to the highest crystallization rate of an overcooled liquid. Transitions of higher order and Curie points are also briefly discussed from the same point of view.

263 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that the activation energy of a chemical reaction with an activation energy is a rapidly fluctuating function of the energy of the system, and the transmission coefficient is a function of this fluctuation.
Abstract: The activated complex or transition state method for calculating the absolute rate of a chemical reaction with an activation energy would be rigorously valid if classical mechanics applied to all degrees of freedom. In quantum mechanics, two kinds of limitations must be considered. First, because of Heisenberg’s uncertainty principle, the transition state itself can be defined only if the potential surface is sufficiently flat around the highest point of the reaction path. Second, even if this condition is fulfilled, the transmission coefficient can differ from the value expected on the basis of classical mechanics, because a wave packet can be reflected both on its way up, and also on its way down the potential barrier separating the initial and final states. In fact, the transmission coefficient is, in many cases, a rapidly fluctuating function of the energy of the system. If the temperature distribution of the energy is sufficiently broad to cover several periods of this fluctuation, an average transmission coefficient can be defined which nearly agrees with the classical value. For the crossing of a one-dimensional potential barrier, the quantum corrections are surprisingly small. In problems with several degrees of freedom, the transmission coefficient is affected by the interchange of translational and vibrational energy. However, if the vibrational motion is fast as compared with the motion along the reaction path, these degrees of freedom can be treated on a par with the electronic coordinates. In this case, the formulas of Eyring, with a mechanically sensible transmission coefficient, are satisfactory. On the whole, we conclude that quantummechanical considerations invalidate the transition state method to a much smaller extent than could be presumed and it is only in the consideration of the relative rates of reactions between isotopes and reactions at very low temperatures that these effects may be important.

241 citations


Journal ArticleDOI
TL;DR: The neglected problem of the theory of the absolute intensities of electronic transitions in molecular spectra is discussed in this paper, where general equations for dipole strength, Einstein coefficients, mean lifetimes of excited states, f values, and so forth are collected in forms convenient for use in later papers where the theory for various types of transitions will be developed and applied.
Abstract: The neglected problem of the theory of the absolute intensities of electronic transitions in molecular spectra is discussed. General equations for dipole strength, Einstein coefficients, mean lifetimes of excited states, f values, and so forth, are collected in forms convenient for use in later papers where the theory for various types of transitions will be developed and applied.

235 citations


Journal ArticleDOI
TL;DR: In this paper, the van der Waals theory of corresponding states is derived on the basis of certain assumptions concerning the properties of the molecules, and by using classical statistics, the Van der Waal theory is derived.
Abstract: On the basis of certain assumptions concerning the properties of the molecules, and by using classical statistics, the van der Waals theory of corresponding states is derived. No mathematical approximations are involved. Argon, krypton and xenon, which conform closely to the assumptions, show the expected correspondence in behavior and are taken as standards. The name perfect liquid is suggested for this behavior. In a second part, the deviations from perfection are discussed for a wide variety of substances. Particularly considered are heat capacities and entropies of vaporization which should be compared at points where the vapor to liquid volume ratio has the same value. The observed deviations are explained in a general way.

235 citations


Journal ArticleDOI
TL;DR: In this article, two related types of high intensity molecular spectra are discussed: charge resonance spectra and charge transfer spectra, which involve transfer of one electron from a bonding to the corresponding antibonding molecular orbital.
Abstract: Two related types of high intensity molecular spectra are discussed. These are designated as charge‐resonance spectra and charge‐transfer spectra. In the molecular orbital approximation, both these types usually involve transfer of one electron from a bonding to the corresponding antibonding molecular orbital. In the atomic orbital approximation, charge‐resonance spectra involve a transition from a symmetrical to a corresponding antisymmetrical state, the wave function of each of these two states being a linear combination of two wave functions representing two hypothetical states of a molecule that are equivalent or nearly so but different in charge distribution. Charge‐transfer spectra in the atomic orbital approximation involve a transition from a state having a non‐ionic to one having an ionic wave function (N→V transition). Theoretical equations for dipole strengths and f values for both these types are given, in each case calculated according to each of the two approximations. The equations are very...

Journal ArticleDOI
TL;DR: In this paper, the theory of rotating axes and polyatomic molecules is extended in a form applicable to linear and anomalous molecules, and applied to a linear tetratomic molecule and to an anomalous ammonia-like molecule, to obtain a Hamiltonian kinetic energy lacking first-order terms.
Abstract: The theory of rotating axes and polyatomic molecules is extended in a form applicable to linear and anomalous molecules. It is applied to a linear tetratomic molecule and to an anomalous ammonia‐like molecule, to obtain, in each case, a Hamiltonian kinetic energy lacking first‐order terms. A second‐order perturbation calculation yields the energy of interaction between rotation and vibration for the linear molecule. The relationship to Howard's theory of ethane is also given.

Journal ArticleDOI
TL;DR: In this paper, the spectra of cyclopentadiene, 1,3-cyclohexadiene and 1, 3-cycloenadiene were considered and the theoretical explanations of their departures from the spectras of open-chain conjugated dienes were given.
Abstract: The spectra of cyclopentadiene, 1,3‐cyclohexadiene, thiophene, furan, and pyrrole are considered. Theoretical explanations of their departures from the spectra of openchain conjugated dienes are given. The cause of these departures in the cases of cyclopentadiene and cyclohexadiene is designated hyperconjugation. This is a mild sort of conjugation, apparently not recognized as such hitherto, between saturated groups and double or triple bonds or even other saturated groups. Observed displacements of spectra toward longer wave‐lengths, and corresponding effects in the refractivities (cf. VI), when alkyl groups are substituted for hydrogens in ethylene, butadiene, benzene, or other double‐bonded compounds, are attributed to hyperconjugation. Further, the decreasing heat of hydrogenation observed with increasing alkyl substitution in these compounds may indicate increasing stability caused by hyperconjugation. However, it is likely according to the theory that appreciable energy effects caused by hyperconjugation are usually restricted to excited states, and so should affect mainly ultraviolet spectra and refractivities. If this is correct, heats of hydrogenation ought not to be much influenced by hyperconjugation, since they depend on the energies of molecules in their normal states. Hence, it is likely that the above‐noted variations in heats of hydrogenation are caused partly or mainly by other causes. Conjugation of triple bonds is briefly discussed, and it is also pointed out that in ethane there must be hyperconjugation which is analogous to the triple‐bond conjugation in cyanogen. It is shown that this hyperconjugation in ethane should not appreciably hinder free rotation. Likewise, hyperconjugation in propylene should produce no barrier to free rotation of the methyl group. It is possible, however, that hyperconjugation may help to restrict free rotation in some cases. Carbon to carbon single bond distances should be slightly shortened by hyperconjugation. The unusually small C–C distance in methylacetylene as determined spectroscopically by Herzberg and co‐workers may perhaps be explained in this way, although in other cases no appreciable effects are apparent. It is helpful to classify examples of hyperconjugation according to various types, which may differ in the magnitudes of their effects. Possibly only first‐order hyperconjugation (between a double or triple bond and a saturated group) is important. Second‐order hyperconjugation (between two saturated groups, as, for example, in ethane) very likely produces smaller effects.

Journal ArticleDOI
TL;DR: In this article, the absorption spectrum of benzene at 2800-2200A was analyzed and the vibrational structure of the system was found to be in agreement with the selection rules for a forbidden transition (1A1g→1B2u).
Abstract: The absorption spectrum of benzene at 2800–2200A has been analyzed. The vibrational structure of the system has been found to be in agreement with the selection rules for a forbidden transition (1A1g→1B2u). The transition becomes possible when vibrations of type Eg+ distort the molecule. Only carbon frequencies have been found to be effective. The interpreted data are collected in series on page 211. The analysis is corroborated by comparison with the absorption of solid benzene at —259°C, with the absorption spectrum of heavy benzene and with the fluorescence spectra of both benzenes.

Journal ArticleDOI
TL;DR: In this article, the applicability of the Born, Karman and Blackman method as a means of approximating the skeletal frequencies of the normal paraffin hydrocarbons is investigated.
Abstract: The method of Born, Karman and Blackman, designed for the determination of the normal modes of crystals, offers interesting possibilities in the case of certain polyatomic molecules possessing structural periodicity. The applicability of the method as a means of approximating the skeletal frequencies of the normal paraffin hydrocarbons is investigated. Although the calculations are not carried beyond the qualitative stage, they provide rather illuminating results.

Journal ArticleDOI
TL;DR: The relation due to Boltzmann between entropy and thermodynamic probability is enunciated in a precise form in this paper and generalized in such a way that each of the other thermodynamic potentials is related in a similar manner to a ''thermodynamic probability'' for which a more suitable name is a ''partition function''.
Abstract: The relation due to Boltzmann between entropy and ``thermodynamic probability'' is enunciated in a precise form. This relation is generalized in such a way that each of the other thermodynamic potentials is related in a similar manner to a ``thermodynamic probability,'' for which a more suitable name is a ``partition function.''

Journal ArticleDOI
TL;DR: In this article, a theory of the radial distribution function in nonpolar liquids composed of spherical molecules is developed and the characteristic features of experimentally determined radial distribution functions are reproduced by the theory.
Abstract: A theory of the radial distribution function in nonpolar liquids composed of spherical molecules is developed The characteristic features of experimentally determined radial distribution functions are reproduced by the theory A single parameter, the work of formation of a cavity of of molecular size, determines the approximate form of the distribution


Journal ArticleDOI
TL;DR: In this article, it was shown that the spin-only formula requires that the ratio of the fourth-to-second-order part of the noncubic portion of the crystalline potential have a certain critical value.
Abstract: As Siegert has shown, the fact that the susceptibilities of both titanium and vanadium alum conform to the ``spin‐only'' formula demands that the ratio of the fourth‐to the second‐order part of the noncubic portion of the crystalline potential have a certain critical value. The present paper investigates whether such a ratio can result from (I) the direct effect of the ``distant'' charges, i.e., the atoms more remote than the six waters immediately surrounding the paramagnetic ion, (II) the indirect action of the remote atoms in distorting or polarizing the water cluster so that it is no longer octohedral, or (III) the Jahn‐Teller effect, whereby the degeneracy of the cation has repercussions on the arrangement of the surrounding waters, so that they are not cubically grouped. It is concluded that (I) does not yield a sufficiently large splitting. That the mechanism (III) cannot alone be effective is shown by Gorter's relaxation experiments, as well as by the existence of a small splitting of the basic quartet of chrome alum which cannot be due to (III), but which is revealed by adiabatic demagnetization experiments. On the other hand, (II) does give a ratio of fourth‐ to second‐order terms of the proper size and sign, and the corresponding departures from octohedral symmetry in the water cluster need not be large enough to contradict x‐ray data. The total splitting is materially amplified by the superposition of (III) on (II). It is gratifying that a model can be found which will thus yield the rather peculiar type of crystalline potential required if the basic orbital states of titanium and vanadium are both nondegenerate, but trigonal, as shown by the susceptibility data. Furthermore, it is shown in Section IV that the model gives a splitting in chrome alum of the order of magnitude 10‐1 cm‐1 and sign deduced by Hebb and Purcell from the magnetization at low temperatures.

Journal ArticleDOI
TL;DR: In this article, the spectral properties of conjugated double-bonded dienes were investigated and it was shown that their ultraviolet spectra should be similar to those of alkenes (C2H4 and derivatives).
Abstract: This paper is the first of a series on the application of intensity calculations to the spectra and related properties of organic compounds containing conjugated or resonating double bonds. It is concluded that in most cases the characteristic strong absorption of such compounds (giving color if the number of conjugated double bonds is large enough) is due to an N→V transition (homopolar normal state→ionic excited state) similar to those already identified in paper II for I2, O2, C2H4, and other molecules.The present paper is devoted primarily to conjugated dienes. Unconjugated dienes and polyenes are treated incidentally, and it is shown theoretically that their ultraviolet spectra should be similar to those of alkenes (C2H4 and derivatives). There should be no strong absorption peak above λ2000, and the intensity per double bond should be about the same as in alkenes. These conclusions are in agreement with the rather scanty experimental data (examples, diallyl, rubber).Detailed calculations are made on...

Journal ArticleDOI
TL;DR: In this paper, the gaseous, liquid, mesomorphous and solid states in monolayers are defined and their close connection with the corresponding states in three dimensions rigorously established.
Abstract: The gaseous, liquid, mesomorphous and solid states in monolayers are defined and their close connection with the corresponding states in three dimensions rigorously established. This involves a new treatment of the two‐dimensional liquid and of its transformation to the mesomorphous state. The properties of the three‐dimensional vitreous state of fatty substances are shown to be particularly important in connection with the behavior of monolayers. The different critical and transformation temperatures are also defined and their significance explained. From this is derived a systematic classification of the different types of isotherms observed. By determining the variations of the compressibility, viscosity and apparent dipole moment with change of area, higher order transformations are detected in monolayers. These transformations occur at the same areas as those at which ordinary phase transformations occur at lower temperatures.

Journal ArticleDOI
TL;DR: In this article, a theory of liquids is presented based on the assumption of the presence of holes in a lattice-like structure and using a method analogous to that used in treating order and disorder in alloys.
Abstract: A theory of liquids is presented based on the assumption of the presence of holes in a lattice‐like structure and using a method analogous to that used in treating order and disorder in alloys. This treatment provides an elementary theory of condensation and a clear and simple treatment of the critical phenomena of liquids and also yields a theoretical curve for the density of vapor and liquid as a function of temperature in agreement with the experimental curve. The existence of more than one phase arises as a consequence of the theory.

Journal ArticleDOI
TL;DR: In this paper, the authors compared the observed absorption spectra of conjugated polyenes and their derivatives with the results of theoretical calculations on various models of butadiene, octatetraene, and β-carotene.
Abstract: The observed absorption spectra of conjugated polyenes and their derivatives are compared with the results of theoretical calculations on various models of butadiene, octatetraene, and β‐carotene. In each case the unsaturation electrons give rise to a series of N→V electronic transitions which spread over an increasing range of the spectrum with increase in the number of conjugated double bonds. According to the theory, the greater part of the whole N→V intensity is concentrated in its longest wave‐length member N→V1, and the latter gets more and more intense as it shifts toward longer wave‐lengths with increase in the number of conjugated double bonds. Exactly this behavior has been observed experimentally in the spectra of the conjugated polyenes and their derivatives. Thus we obtain a satisfactory theoretical explanation of the existence of strong color in polyene pigments and related compounds, i.e. in the carotenoids. Quantitatively, the theory (when the rough Huckel molecular orbital approximation i...

Journal ArticleDOI
TL;DR: It is shown by means of the theory of absolute reaction rates that the current density I at an electrode is related to the overvoltage V by the expression I = I0eαVF/RT, where I0 is a constant for a given electrode, representing the current passing in each direction at the reversible potential.
Abstract: It is shown by means of the theory of absolute reaction rates that the current density I at an electrode is related to the overvoltage V by the expression I = I0eαVF/RT where I0 is a constant for a given electrode, representing the current passing in each direction at the reversible potential, and α is the fraction of the added potential V operating between the initial and activated states. Since α is about 0.5 for many electrodes, it appears that the energy barriers at the electrode surface is a symmetrical one. The quantity I0 is equal to Be—ΔH1‡/RT, where ΔH1‡ is the heat of activation of the rate‐determining process responsible for overvoltage, and B is C1(kT/h)F/N·eΔS1‡/R, where k, h, F, N and R are universal constants, T is the temperature, ΔS1‡ is the entropy of activation and C1 is the concentration, per unit area, of the species involved in the slow process. Since ΔH1‡ and I0 can be obtained from experimental data, it is possible to evaluate B, which is found to be independent of the nature of th...

Journal ArticleDOI
TL;DR: In this article, the authors attributed the intensification of ultraviolet absorption in substituted over unsubstituted benzene to the destruction of the sixfold symmetry of the benzene by the partial migration of an electron to the ring or out of it.
Abstract: The intensification of ultraviolet absorption in substituted over unsubstituted benzene is here attributed to the destruction of the sixfold symmetry of the benzene by the partial migration of an electron to the ring or out of it. Toluene, aniline, phenol, and fluorobenzene are treated. The electric moment produced by a migration of an electron from the radical into the benzene ring is calculated by the method of antisymmetric molecular orbitals and the extent of migration by a minimum condition. The results are in agreement with empirical data. It is concluded that a radical will produce a large intensification of the absorption if it has a low ionization potential, a pair of nonbonding P electrons, and a not too large ring‐radical distance. On this basis the SH group is predicted to be very effective.

Journal ArticleDOI
TL;DR: In this paper, a comparison of the proton attracting properties of different solvents was made, based on the magnitude of the shifts in the OD fundamental band of CH3OD, and the results gave proof of the wide occurrence of hydrogen bonding between unlike molecules.
Abstract: The use of isotopic hydrogen has made possible an extension of the study of hydrogen bonds between unlike molecules to include many new types of donor solvents. From the magnitude of the shifts which the different solvents produce in the OD fundamental band of CH3OD, a comparison of the proton‐attracting properties of the different solvents can be made. It is suggested that this method may be used as a practical means of comparing the intrinsic strength of organic bases. Solvents representative of the classes—nitro‐compounds, esters, aldehydes, ketones, ethers, nitriles and amines—were employed, and the results give proof of the wide occurrence of hydrogen bonding between unlike molecules.

Journal ArticleDOI
TL;DR: In this paper, the Raman spectrum of liquid triborine triamine has been studied, and the infra-red absorption of the gas measured from 2.5 to 24.5μ.
Abstract: The Raman spectrum of liquid triborine triamine has been studied, and the infra‐red absorption of the gas measured from 2.5 to 24.5μ. The molecule is assumed to be isoelectronic with benzene, belonging to the point group D3h, and an assignment of fundamental frequencies is given, based upon this structure. A normal coordinate treatment has been made, and used to calculate the three inactive frequencies and the isotope shifts due to the B10 isotope. The agreement between calculated and observed values is satisfactory except for the nonplanar frequencies, where strong interactions between bonds attached to the aromatic ring in metapositions are indicated. The fundamental frequencies of triborine triamine are compared with those of benzene; satisfactory correlation is obtained with the benzene frequencies given by Lord and Andrews. The frequencies of the triborine triamine are used together with structural data to calculate the thermodynamic properties of the substance.

Journal ArticleDOI
TL;DR: In this article, a modified valence force type potential function containing interaction terms between the two methyl groups is found to fit the fundamental frequencies of the light and heavy ethanes quite well, and it is concluded that the equilibrium configuration of ethane cannot be reliably determined from the analysis of the data available on the vibrational spectra of C2H6 and C2D6.
Abstract: The infra‐red spectrum of gaseous C2D6 has been investigated from 2 to 22μ, and the Raman spectrum of the liquid has been photographed. These data have been analyzed for both the symmetries D3d and D3h. It is concluded that the equilibrium configuration of ethane cannot be reliably determined from the analysis of the data now available on the vibrational spectra of C2H6 and C2D6. However, the ``uncertain frequency'' of C2H6 is determined by application of the product rule if the symmetry is D3d. A modified valence force type potential function containing interaction terms between the two methyl groups is found to fit the fundamental frequencies of the light and heavy ethanes quite well.

Journal ArticleDOI
TL;DR: The photolysis of acetone and of formaldehyde takes place principally through a free radical mechanism, and the primary processes consist in the splitting off of a methyl radical and a hydrogen atom, respectively.
Abstract: The photolysis of acetone and of formaldehyde takes place principally through a free radical mechanism. The primary processes consist in the splitting off of a methyl radical and a hydrogen atom, respectively. The primary process in the photolysis of methyl ethyl ketone also consists in the splitting off of either a methyl or an ethyl radical. The heat of dissociation of the first hydrogen in formaldehyde is shown to be as low as 78 kcal. Approximately 26 kcal. is required to remove the second hydrogen atom.

Journal ArticleDOI
TL;DR: In this article, the absorption spectrum of BF3 has been studied under high resolution from 400 cm to 3000 cm and the active fundamentals v2, v3 and v4 and the overtone 2v3 have been observed.
Abstract: The infra‐red absorption spectrum of BF3 has been studied under high resolution from 400 cm—1 to 3000 cm—1. The active fundamentals v2, v3 and v4 and the overtone 2v3 have been observed. The parallel fundamental v2 has been partially resolved and the value of the moment of inertia A found to be 79×10—40 g cm2. The B–F distance is 1.29×10—8 cm. The isotope effect due to the two isotopes of boron was observed in all bands. The appearance of the unresolved bands v4 and 2v3 is shown to be greatly influenced by the interaction between vibration and rotation.