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1 Dec 1936

Volume 4, Issue 12, pp. 751-784


The Ultraviolet Absorption Spectra of Simple Hydrocarbons I. n‐Heptene‐3 and Tetramethylethylene

Emma P. Carr and Margery K. Walker

J. Chem. Phys. 4, 751 (1936); http://dx.doi.org/10.1063/1.1749786 (5 pages) | Cited 14 times

Online Publication Date: 22 December 2004

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The ultraviolet absorption spectra of n‐heptene‐3 and tetramethylethylene were measured in liquid and hexane solution phase, between 4000A and 2100A and in vapor phase between 2300A and 1500A. Curves showing the logarithm of the molecular extinction coefficient as a function of the wave number are given for the measurements in the quartz region and tables giving the regions of absorption together with the wave‐lengths of the centers of bands for the measurements with the fluorite vacuum spectrograph. Comparison with earlier work shows the progressive shift toward the visible of the absorption bands in the Schumann region as the hydrogen atoms of ethylene are replaced by alkyl groups, and the parallelism between the spectra of different hydrocarbons having the same configuration with respect to the double bond.

The Ultraviolet Absorption Spectra of Simple Hydrocarbons II. In Liquid and Solution Phase

Emma P. Carr and Gertrude F. Walter

J. Chem. Phys. 4, 756 (1936); http://dx.doi.org/10.1063/1.1749787 (5 pages) | Cited 7 times

Online Publication Date: 22 December 2004

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Molecular extinction coefficients for twelve olefine hydrocarbons have been determined between λ = 3300A and 2100A and are given in the form of curves showing the logarithm of the extinction coefficient as a function of the wave number. The beginning of absorption, as measured by log ϵ = — 2.0, is quite characteristic of the number of alkyl groups bound to the carbon atoms of the double bond and is only very slightly affected by the nature of the alkyl group.

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

Emma P. Carr and Hildegard Stücklen

J. Chem. Phys. 4, 760 (1936); http://dx.doi.org/10.1063/1.1749788 (9 pages) | Cited 45 times

Online Publication Date: 22 December 2004

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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 to the transition 1A1→1B1, predicted for the ethylene molecule. Usually one, but never more than three bands of this system could be seen because of overlapping with another group of bands of higher intensity. All of the sixteen olefines have this same intensity change, showing the existence of another electronic excitation. A third group of bands corresponding to a third electronic excitation can be seen clearly in the spectra of four hydrocarbons and may possibly be present but overlapping the lower frequency group in the other compounds. The bands are too broad and diffuse to admit of analysis of vibrational structure but certain recurring separations, which are probably related to the 1350 cm—1 vibrational frequency of ethylene, are evident. In the molecules of higher symmetry, where fewer transitions are permitted by the selection rules, there is less overlapping and therefore more discrete bands can be seen.

The Infrared Absorption Spectra of Dioxane‐Water Mixtures

Walter Gordy

J. Chem. Phys. 4, 769 (1936); http://dx.doi.org/10.1063/1.1749789 (3 pages) | Cited 11 times

Online Publication Date: 22 December 2004

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The absorption spectra of various dioxane‐water mixtures have been studied in the region 2.5μ to 6.5μ. Dioxane was found to produce marked changes in the water spectrum. The observed variations are more pronounced for low water concentrations. Association of the water and dioxane molecules is suggested as a possible explanation of the observed effects.

Vibration Spectra and Molecular Structure I. General Remarks and a Study of the Spectrum of the OH Group

R. B. Barnes, L. G. Bonner, and E. U. Condon

J. Chem. Phys. 4, 772 (1936); http://dx.doi.org/10.1063/1.1749790 (7 pages) | Cited 5 times

Online Publication Date: 22 December 2004

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A brief survey is given of the ideas underlying the interpretation of molecular vibration spectra in connection with molecular structure problems. This is followed by a discussion of the reasons for the appearance or nonappearance in the spectrum of the characteristic frequency at 3400 cm—1 for various molecules containing the OH group. In certain alcohols and glycols this frequency has not been reported in the Raman effect, but it is concluded that this must be due to experimental difficulties. In the carboxylic acids, on the other hand, as well as in certain aromatic compounds containing OH, the characteristic frequency is definitely absent from both the Raman and infrared spectra, and the role of the hydrogen bond in association and chelation is discussed in connection with these cases.

The Relative Atomic Weight of Oxygen in Water and in Air II. A Note on the Relative Atomic Weight of Oxygen in Fresh Water, Salt Water and Atmospheric Water Vapor

Malcolm Dole

J. Chem. Phys. 4, 778 (1936); http://dx.doi.org/10.1063/1.1749791 (3 pages) | Cited 1 time

Online Publication Date: 22 December 2004

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Purified Lake Michigan water appears to be nearly exactly intermediate in density between purified Atlantic Ocean water and water condensed from the atmosphere. Within the experimental error the entire difference in density between fresh and salt water appears to be due to differences in the oxygen isotopic ratios. The bearing of these results on theories explaining the relatively large concentration of O18 in the atmosphere is discussed.

Kinetics of OH Radicals as Determined by Their Absorption Spectrum II. The Electric Discharge Through H2O2

A. A. Frost and O. Oldenberg

J. Chem. Phys. 4, 781 (1936); http://dx.doi.org/10.1063/1.1749792 (4 pages) | Cited 9 times

Online Publication Date: 22 December 2004

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In order to study the kinetics of OH radicals in H2O2 the concentration of OH as a function of time is measured by the decay of the intensity of the OH absorption bands after interrupting an electric discharge through H2O2. For each snapshot a new supply of H2O2 is introduced into the absorption tube and partly decomposed into OH+OH by an electric discharge of brief duration. OH radicals disappear in H2O2 much more rapidly than in H2O. This indicates a bimolecular reaction OH+H2O2. The emission spectrum of OH shows abnormal rotation of OH even more strongly when excited in H2O2 than in H2O, the rotation being determined not by the temperature but by the simultaneous dissociation and excitation producing the OH radicals observed.

Solvent Action on Optical Rotatory Power

Charles O. Beckmann and Karl Cohen

J. Chem. Phys. 4, 784 (1936); http://dx.doi.org/10.1063/1.1749793 (1 page) | Cited 19 times

Online Publication Date: 22 December 2004

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A general theory of the optical rotatory power of liquids is developed. The method of C. G. Darwin, supplemented so that the fundamental quantities Sαβγ...† which appear there are related to the properties of the molecules comprising the medium, is followed. The optical properties of a molecule are given by a set of tensors σ′ αβγ.... The concept of deformation leads naturally to a simple relation between the σ′ αβγ...'s and the field acting on the molecule. The electrostatic field of the dipoles of the surrounding molecules is computed for the limiting cases of imperfect gases and dilute solutions, for molecules of simple geometrical configuration. This field is identified with the solvent field. For these idealized systems, the rotatory power of a molecule in various solvents is determined in terms of quantities characteristic of the solvents. The resulting equations are controlled by comparing with the behavior of actual liquids.
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