E. F. Barker

The Infra‐Red Absorption Spectrum of Methyl Alcohol

Using a grating spectrometer having a KBr foreprism the spectrum of methyl alcohol vapor was studied in the region from 2.5 to 26μ. This molecule has bands at 3683, 2978, 2845, 2054, 1477, 1455, 1340, 1034.18 cm—1 and a very broad band extending from 860 to beyond 380 cm—1. These bands are typical perpendicular and parallel bands and indicate that the molecule is only slightly asymmetric.From the fine structure of the 1034.18 cm—1 parallel band and from certain assumptions about the structure of the molecule the two largest moments of inertia, A and B, were found to be 35.18 and 33.83×10—40 g cm2, respectively. It was not possible to measure C directly but it was estimated to be approximately 6.8×10—40 g cm2.The low frequency band is probably due to the vibration of the hydroxyl hydrogen atom perpendicular to the O–H bond and perpendicular to the figure axis of the molecule. The presence of this band indicates that the hydroxyl group is not free to rotate, at least in the ground state. There is evidence o...

The Infra‐Red Absorption Spectra of Ethylene and Tetra‐Deutero‐Ethylene under High Resolution

The fine structure of several infra‐red absorption bands of C2H4 and C2D4 have been resolved. From the rotational constants so found, the C–C and C–H distances in this molecule were calculated to be 1.353 and 1.071A, and the H–C–H angle to be 119°55′. An assignment of fundamental frequencies has been made which is consistent with the observed data.

The Infra‐Red Absorption Spectrum of Boron Trifluoride

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.

The Infrared Spectrum of Heavy Water

Samples of water vapor containing 90 and 40 percent of deuterium have been examined in the infrared, and the absorption bands v2 and v3 for D2O and v2 and v1 for HDO have been located. The position of v1 for D2O is known from Raman scattering. Of the nine fundamental frequencies for the three varieties of water, eight have now been observed. The ninth, v3 for HDO, should lie very close to the corresponding band for H2O and is apparently completely masked. Computed values of these frequencies already available agree very well with the measured ones. A fair degree of resolution is obtained in the bands v2. The fine structure observed agrees approximately with that predicted by using the molecular dimensions obtained by Mecke, viz., OH distance ∼0.95×10—8 cm and apex angle ∼105°. The magnitude of the interactions is so great, however, that precise determinations of these constants must await a more complete solution of the mechanical problem.

The Infra‐Red Absorption Spectrum of Diborane

The infra‐red absorption spectrum of diborane has been examined under high resolution from 3.7μ to 30μ with automatic recording grating spectrometers. The rotational fine structure in two bands of each of the three types characteristic of asymmetric top molecules has been measured. All results and observations are consistent with the conclusion that diborane has the bridge structure, and belongs to the same symmetry point group, Vh, as ethylene. The observation and structure of the band with center at 368.7 cm−1 provides spectroscopic evidence that the molecule is non‐planar, and makes more definite the assignment of fundamental frequencies. Data on all bands fit quite well the symmetric top approximation, since accidentally two principal moments of inertia are approximately the same, and calculations yield accurate values for certain rotational constants.

On the Infrared and Raman Spectra of Methyl Compounds

An analysis of the resonance interaction between the vibrations v1 and 2v4 in the methyl halide molecules explains the appearance of the very intense extra band in the infrared and Raman spectra of these molecules. This degeneracy is evidently characteristic of the methyl group. A number of molecules involving the methyl group and exhibiting the phenomenon of the extra band are listed.

The Infrared Absorption Spectrum of Methyl Deuteride

The six fundamental vibrational frequencies of methyl deuteride were observed and the fine structure of the bands resolved. The frequencies are v6 = 1156.3, v5 = 1306.8, v4 = 1477.1, v3 = 2205.25, v1 = 2983.0, v2 = 3031.0. From the fine structure of the bands, the moments of inertia are found to be IA=7.166×10−40 g cm2,IC=5.298×10−40 g cm2 and the internuclear distances are C–H=1.093×10−8 cm,  H–H=1.785×10−8 cm. From the four previously known frequencies of methane and each of the frequencies of this molecule, the values of the five potential constants are computed. Three of the sets are consistent and agree well with the values found by Dennison and Johnston, but the other three sets have either negative or imaginary values. The frequencies from which these are calculated are the ones which take part in a resonance interaction which was not included in the theory. From the observed spacings of the zero branches of the perpendicular bands, extreme ranges of the rotation‐vibration interaction factors are c...

The Infra‐Red Absorption Spectrum of Methyl Amine

The parallel type methyl amine band at 10μ has been resolved. Its center is at 1045.27 cm—1, and the very regular structure of its P and R branches indicates a close approximation to axial symmetry. The mean of the two largest moments of inertia is 37.43 × 10—40 g·cm2. Assuming angles and distances for NH2 as in ammonia, and for CH3 as in methane, the C–N distance is computed to be 1.48 × 10—8 cm. Certain enhanced lines suggest a superposed perpendicular band. The 13μ band is partially resolved, and assigned to a motion corresponding to v3 in NH3. The bands arising from vibrations characteristic of the amino and methyl groups have been examined but could not be resolved.

The Infra‐Red Absorption Spectra of CH3OD and CH2DOD

The infra‐red absorption spectra of CH3OD and CH2DOD between 2.5μ and 24μ have been examined with a KBr prism spectrometer, and with appropriate gratings. The observed bands represent all of the fundamental vibrations except the one of lowest frequency which is associated with torsional vibrations about the C–O bond. Since these molecules depart only slightly from axial symmetry, the bands, with the exception of three due to the hydroxyl radical, correspond in position and appearance to those of the methyl halides. The rotational structure for the 10μ band (v5) of CH3OD has been resolved, and partial resolution is obtained in some other bands. The band v5 in CH2DOD has two components arising probably from two forms of the molecule in which the hydroxyl D atom occupies different valleys of the threefold potential. The deformation vibration (v7) is single for CH3OD but has four components in CH2DOD, indicating a separation of levels which for the former molecule are degenerate. A comparison of the frequenci...

The Infra‐Red Absorption Spectrum of Propane

Of the twenty‐seven internal degrees of freedom of propane, all nondegenerate, twenty‐two may appear as fundamental absorption bands. These bands fall into three symmetry classes, designated A1, B1 and B2, and distinguishable by their characteristic contours. Because of overlapping, however, it is impossible in many cases to determine their positions precisely. This is especially true in the regions of the C–H valence and deformation frequencies. Some ten or twelve fundamental bands may be identified with confidence as well as a number of combinations. An A1 band at 870 cm—1 and a B2 band at 748 cm—1 have been partially resolved, the line spacing being about 1.47 cm—1 in agreement with predictions based upon electron diffraction measurements. The fine structure of the B1 bands has not been observed (the predicted spacing is 0.5 cm—1) but the interval between maxima of the P and R branches is approximately 26 cm—1 as expected. With 24 cm‐atmospheres of gas no bands were observed between 15μ and 35μ, althou...