Arnold G. Meister

Substituted Methanes. III. Raman Spectra, Assignments, and Force Constants for Some Trichloromethanes

Raman displacements, semiquantitative relative intensities, and precise depolarization factors for trichloromethane, fluorotrichloromethane, and bromotrichloromethane were obtained in the liquid state. Several overtones and combination bands hitherto unreported are given and frequency assignments are made. The Raman data in the literature for CCl3H, CCl3D, CCl3F, CCl4, and CCl3Br in the liquid state have been collected and the probable values ascertained. Force constants in modified valence force potential functions containing all possible interaction constants were calculated for the five molecules.

Substituted Methanes. X. Infrared Spectral Data, Assignments, Potential Constants, and Calculated Thermodynamic Properties for CF3Br and CF3I

Infrared wave numbers, relative intensities, and percent transmission curves have been obtained for CF3Br and CF3I in the region 400–2200 cm−1. Assignments are given for the observed bands, in which the assignments of Plyler and Acquista for ν2 and ν3 are interchanged. Potential constants were calculated for both molecules by the Wilson FG matrix method. And, finally, the heat content, free energy, entropy, and heat capacity for the ideal gaseous state at 1 atmos pressure were calculated for 12 temperatures from 100°to 1000°K, using a rigid rotator, harmonic oscillator approximation.

Substituted Methanes. I. Raman and Infra‐Red Spectral Data, Assignments, and Force Constants for Some Tribromomethanes

As a part of a systematic investigation of the vibrational spectra of substituted methanes and ethanes, Raman displacements, semiquantitative relative intensities, quantitative depolarization factors, and infra‐red absorption frequencies in the region 700–5000 cm−1 have been obtained for CBr3H, CBr3Cl, and CBr4. Details about the design of the infra‐red spectrograph are given. The Raman and infra‐red spectral data in the literature for CBr3H, CBr3D, CBr3F, CBr3Cl, and CBr4 have been collected, tabulated, and critically examined in comparison with the present results and a decision was made as to the probable values of the Raman and infra‐red data at the present time. Assignments of the observed Raman and infra‐red bands, consistent with the selection rules, were made for all of the molecules. Finally, force constants were calculated for the five molecules, using a potential energy function containing all possible second degree terms.

Substituted Methanes. VIII. Vibrational Spectra, Potential Constants, and Calculated Thermodynamic Properties for Dibromodichloromethane

Raman displacements, semiquantitative relative intensities, and quantitative depolarization factors for the liquid, and infrared absorption wave numbers and percent transmission curves for both the liquid and the gas, have been obtained for CBr2Cl2. The present and previous data were critically examined and probable values of the wave numbers corresponding to the fundamental vibrational frequencies were determined. Assignments were made for all observed Raman and infrared bands. As a check on the assignments, a normal coordinate treatment was undertaken, using a potential function containing all possible quadratic interaction constants. A reasonable set of potential constants was obtained. The observed fundamentals then were used to calculate to a rigid rotator, harmonic oscillator approximation the heat content, free energy, entropy, and heat capacity for 12 temperatures from 100° to 1000°K, for the ideal gaseous state at 1‐atmos pressure.

Substituted Ethanes. III. Raman and Infrared Spectra, Assignments, Force Constants, and Calculated Thermodynamic Properties for 1,1,1‐Trichloroethane

Raman displacements, semiquantitative relative intensities, and quantitative depolarization factors for liquid 1,1,1‐trichloroethane, and infrared wave numbers and percentage absorption for both the liquid and gaseous states in the region 400–5000 cm−1 were obtained and compared with previous data. A normal coordinate treatment, using the Wilson FG matrix method, was carried out, and a reasonable set of force constants was determined. Assignments were made for all observed bands of the infrared and Raman spectra. The heat content, free energy, entropy, and heat capacity at constant pressure were calculated for 9 temperatures in the range 298.16° to 1000°K. A comparison of calculated and observed entropy values indicated that the potential barrier hindering the internal rotation is about 2840 cal/mole, which leads to a value of 205±20 cm−1 for the torsional frequency and to 0.786×10−12 erg/radian for the torsional force constant.

Calculation of rotational distortion constants for some axially symmetric ZX3Y molecules

Abstract The changes of the moment of inertia with respect to the symmetry coordinates of an axially symmetric ZX3Y molecule are evaluated. With these derivatives and formulas in the literature, explicit equations can be written for the rotational distortion constants DJ, DJK, and DK in terms of the masses, internuclear distances, interbond angles and (F−1)ij the elements of the matrix inverse to the potential energy matrix. Rotational distortion constants are then calculated for CCl35H3, CBr79H3, CHF3, CCl335H, CBr79F3, and CIF3. The agreement with previously reported experimental data is fair, except for CCl335H.

Force Constants and Frequency Assignments for Some Substituted Methylacetylenes

Force constants have been determined for methylacetylene using the Wilson FG matrix method. It was found that of the thirteen force constants required for the potential energy function for methylchloroacetylene, methylbromoacetylene, and methyliodoacetylene, eight could be transferred from the set obtained for methylacetylene. Since only four of the ten fundamental frequencies of the methylhaloacetylenes were used in establishing the force constants, all the frequencies were calculated to see if the sets of force constants for the methylhaloacetylenes were reasonable. With the exception of one frequency, the agreement between the calculated and observed values was within two percent. As the calculations served to identify the fundamental frequencies for the methylhaloacetylenes, it was found that previous assignments by Cleveland and Murray of the observed Raman frequencies for methylbromoacetylene and methyliodoacetylene had to be modified. New assignments are given for some of their observed values for ...

On the “redundant coordinate” problem in the rotational-vibrational spectra of polyatomic molecules

Abstract A consistent method is described for treating redundant coordinates in the Wilson treatment of the rotational-vibrational problem of polyatomic molecules. This method furnishes a unique set of potential constants for molecules having redundant internal coordinates. Techniques are developed which permit the calculation of the rotational distortion constants by use of the internal coordinates. A method is given for obtaining the partial derivatives of the moment of inertia tensor with respect to the internal coordinates which is applicable even when redundant coordinates are present. The results for a ZX 3 Y molecule are tabulated in matrix form.

Substituted Methanes. VI. Force Constants and Calculated Thermodynamic Properties for Some Trifluoromethanes

Using previous Raman and infrared data, force constants were calculated for CF4, CF3H, and CF3Cl, by means of the Wilson FG matrix method, with a potential energy function containing all possible second‐degree terms. Fundamental frequencies for CF3D were then determined by means of the force constants found for CF3H. Finally, the heat content, free energy, entropy, and heat capacity for the ideal gaseous state at 1 atmos pressure were calculated for these 4 molecules for 11 temperatures, from 100°K to 1000°K, with a rigid rotator, harmonic oscillator approximation.

Raman and Infrared Spectral Data, Assignments, Potential Constants, and Calculated Thermodynamic Properties for Oxalyl Chloride

Raman displacements, semiquantitative relative intensities, quantitative depolarization factors (single‐exposure method), and infrared wave numbers have been obtained for liquid oxalyl chloride (ClOC–COCl) at room temperature. A critical examination of the present and previous data has been made and probable values have been determined. Normal coordinate treatments have been made for both the cis‐ and trans‐forms. A satisfactory assignment of the present and previous Raman and infrared bands has been made, assuming the sample to be in the trans‐form. Only binary combinations and 1st overtones were used, except for the 2 highest bands at 3740 and 5140 cm−1. Fermi resonance occurs in 4 cases. Not more than 10 percent of the cis‐form can be present, and the presence of even this much rests solely upon Saksena and Kagarises reported temperature variation in the intensity of the 533‐cm−1 Raman band, though the normal coordinate treatment does indicate that the strongest trans‐Raman line at 620‐cm−1 could occu...