Lyman G. Bonner

Vibration Spectra and Molecular Structure IV. The Infra‐Red Absorption Spectra of the Double and Single Molecules of Formic Acid

In the present study the absorption spectrum of formic acid vapor between 1 and 15.5μ has been investigated under a variety of temperature conditions. The spectrum at room temperature gives essentially the absorption of the double molecules alone, while that at 140°C gives the absorption of the single molecules. The results are interpreted in terms of the hydrogen bonding existing in the double molecule. In addition an attempt to prepare and investigate pure formic acid‐d is reported.

Vibration Spectra and Molecular Structure II. The Force Constants of the C–C and C–O Bonds in Organic Molecules

Force constants are calculated from known vibration frequencies for several of the simpler organic molecules by an approximate method involving neglect of the interactions between motions of hydrogen atoms and other atoms. Frequency expressions are given for several special forms of the triatomic molecule, and the C–C and C–O force constants are calculated for ethane, propane, cyclopropane, ethylene oxide, ethyl alcohol, isobutane, dimethyl ether, and methyl alcohol. The values obtained are, in general, in the neighborhood of 3.8 and 4.5×105 dynes/cm, respectively.

Vibration Spectra and Molecular Structure. III The Infrared Absorption Spectra of Cyclopropane and Ethylene Oxide

With a rocksalt prism spectrometer, the infrared absorption spectra of gaseous cyclopropane and ethylene oxide have been mapped in the region 1–15.5 μ. Cyclopropane shows bands at 6250, 4425, 3086, 2525, 2088, 1887, 1739, 1429, 1021, 860, and 671 cm‐1, while ethylene oxide absorbs at 6211, 4310, 3891, 3021, 2632, 2304, 2024, 1733, 1626, 1493, 1255, 1134, 862, 804 and 696 cm‐1. In addition to these infrared measurements, a redetermination was made of the Raman spectrum of liquid ethylene oxide. Raman lines appeared at 807, 867, 1123, 1269, 1488, 2914, 2958, and 3007 cm‐1.

Filters for the Infrared

A simple filtering system, involving the use of only two simply constructed selenium powder filters, is described, by the use of which it is possible to obtain a pure energy spectrum with a wire grating spectrometer in the region 40–130μ. In addition transmission curves are given for a number of substances in the regions 1–15μ and 35–130μ.

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

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.

Vibration Spectra and Molecular Structure

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.