S. Sundaram

Potential Energy Constants, Rotational Distortion Constants, and Thermodynamic Properties for NH3, ND3; PH3, PD3; AsH3, and AsD3

Normal coordinate analyses have been made for ammonia (NH3), phosphine (PH3), and arsine (AsH3) by the Wilson FG matrix method. Using the data on anharmonicities, and the corresponding completely deuterated molecules, the constants of the most general quadratic potential energy function have been obtained for all these molecules. Based on the technique of Kivelson and Wilson, the rotational distortion constants of all the 6 molecules have been determined and compared with the results obtained from previous rotational spectral data. The molar thermodynamic properties, heat content, free energy, entropy, and heat capacity also have been calculated for temperatures from 100 to 1000°K for the ideal gaseous state at 1 atmos pressure and for a rigid‐rotor, harmonic‐oscillator approximation.

Substituted methanes: Part XXXIV. Raman and infrared spectral data and calculated thermodynamic properties for CH2Cl2, CHDCl2, and CD2Cl2☆☆☆

Raman displacements, semiquantitative relative intensities, and approximate depolarization ratios were obtained for liquid CH2Cl2, CHDCl2, and CD2Cl2; and wave numbers and estimated relative intensities for the infrared bands from 400 to 4000 cycles/cm were obtained for both the liquid and the gas. Vibrational assignments for the deuteriated compounds were made by comparison with the results for CH2Cl2, and by application of the complete isotopic substitution rules of Brodersen and Langseth. The results confirm the infrared work of Shimanouchi and Suzuki for these compounds, except for the σ2 fundamental of CD2Cl2 which was assigned to the 1052 cycles/cm Raman line. Thermodynamic properties (heat content function, free energy function, entropy, and heat capacity) were calculated for twelve temperatures from 100 to 1000°K to a rigid-rotor, harmonic-oscillator approximation.

Potential Energy Constants, Rotational Distortion Constants, and Thermodynamic Properties of Methylacetylenes

A special iterative method of obtaining the potential energy constants from vibrational and rotational spectra has been developed. The method has been applied to determine the potential energy constants of some methylacetylenes. The fundamental vibrational frequencies of the deuteriated and tritiated isotopic forms of the acetylenes have been calculated by transferring the force constants. The nonvanishing moments of the inertia tensor derivatives have been obtained for a CY3C≡CX type of molecule. Using a perturbation treatment, the rotational distortion constants DJ, DJK, and DK for these symmetric rotor molecules have been evaluated. These values have been compared with the values from microwave experiments where such data are available. The thermodynamic properties (heat capacity, heat‐content function, free‐energy function, and entropy) have been computed from the vibrational wave numbers for all the molecules. These calculations are based on a rigid‐rotor harmonic‐oscillator approximation for the ide...

Potential Energy Constants, Rotational Distortion Constants, and Thermodynamic Properties of B11H3CO, B11D3CO, B10H3CO, and B10D3CO

Potential energy constants have been obtained for the BH3CO molecule by use of the Wilson FG matrix method. The derivatives of the moments of inertia tensor components, with respect to the symmetry coordinates, of an axially symmetric ZX3YW molecule of C3v symmetry have been evaluated. With these derivatives and the elements of the potential energy matrices, the rotational distortion constants for B11H3CO, B11D3CO, B10H3CO, and B10D3CO have been calculated. The calculated values are in good agreement with the values obtained in the microwave experiments by Gordy et al. The heat content, free energy, entropy, and heat capacity have been calculated for the four molecules for the ideal gaseous state at 1 atmos pressure, with a rigid‐rotor harmonic‐oscillator approximation.

Wave numbers, rotational distortion, constants and thermodynamic properties for NT3, PT3, and AsT3

Abstract The harmonic wave numbers for NT 3 , PT 3 , and AsT 3 have been calculated by use of the potential energy constants obtained for the corresponding hydrides and deuterides in a previous investigation by the authors. The anharmonicity factors and therefore the expected spectral frequencies have been evaluated. A first-order perturbation calculation of the rotational distortion constants for the molecules has been made. The molar thermodynamic properties have been obtained from 100 to 1000°K for a rigid-rotor, harmonic-oscillator approximation at 1-atmos pressure.

Harmonic wave numbers, rotational distortion constants, and thermodynamic properties for partially deuterated and tritiated molecules of the type XYZ2 (X = N, P, or As; Y, Z = H, D, or T)

Abstract Using a harmonic potential energy function, the harmonic wave numbers for partially deuterated and tritiated molecules of the type XYZ 2 ( X = N, P, or As; Y , Z = H, D, or T) have been calculated by the Wilson FG matrix method. The rotational distortion constants for all these molecules also have been calculated on the basis of the first-order perturbation theory of Kivelson and Wilson. Further, with the calculated wave numbers, the molar thermodynamic properties have been obtained for 12 temperatures between 100 and 1000°K for the ideal gaseous state at one atmosphere pressure and for a rigid-rotor, harmonic-oscillator approximation.

Potential Energy Constants, Rotational Distortion Constants, and Thermodynamic Properties of H2C=C=O and D2C=C=O

As a check on the assignments of the fundamentals of ketene (H2C=C=O), a normal coordinate analysis has been carried out and the constants for the general quadratic potential energy function for this molecule have been obtained. Using these constants, the fundamental vibrational wave numbers for the deuteroketene have been calculated, and compared with the observed bands reported for this molecule. The moments of inertia tensor derivatives for the general X2YXW molecule have been obtained. The rotational distortion constants for H2C=C=O and D2C=C=O have been determined. The molar thermodynamic properties—heat content, free energy, entropy, and heat capacity—have been calculated for both molecules for various temperatures from 100° to 1000°K at atmospheric pressure for the rigid‐rotor, harmonic‐oscillator approximation.

Potential energy constants and vibrational amplitudes for thionyl tetrafluoride

Abstract A set of potential energy constants was obtained for the SOF4 molecule from the vibrational spectral data. The axial SF and equatorial SF stretching force constants are 5.5400 and 4.3950 md/A, respectively. The mean square amplitudes of vibration also were determined from the potential energy constants by use of Cyvins secular equation method. The root-mean-square amplitudes for the axial SF, equatorial SF, and SO distances are 4.060, 4.545, and 3.617 pm, respectively, (1 pm = 1 picometer = 10−2A).

Substituted methanes part XXXIII. Mean square amplitudes, rotational distortion constants, and shrinkage constants for CF4, CCl4, and CBr4☆

Abstract Using the potential energy constants obtained in previous investigations in this laboratory, the mean square amplitudes of vibration of CF 4 , CCl 4 , and CBr 4 were calculated by the secular equation method. The mean square amplitudes tudes σ r ( r = C X ; X = F, Cl, and Br) at 298.16°K for CF 4 , CCl 4 , and CBr 4 are, respectively: 18.76, 24.84, and 26.43 pm 2 (1 pm 2 = 10 −24 m 2 = 10 −4 A 2 ). The corresponding mean square amplitudes σ d ( d = X ⋯ X ) are 29.36, 46.36, and 58.77 pm 2 . For CCl 4 , the values of the root mean square amplitudes σ r 1 2 and σ d 1 2 , calculated at 295°K, are, respectively, 4.98 and 6.77 pm ( p = pico = 10 −12 ); the corresponding experimental values are 5.05 and 6.96 pm. The calculated values of the shrinkage constants δ for CF 4 , CCl 4 , and CBr 4 are, respectively, 0.20, 0.35, and 0.44 pm. The rotational distortion constants of CF 4 , CCl 4 , and CBr 4 are, respectively: D J -1650, 176.7, and 26.5 c/s; D Jr -1156, 132.9, and 21.1 c/s.

Substituted methanes: Part XXXVII. Raman and infrared spectral data, and calculated wave numbers for CD2BrCl and CHDBrCl

Abstract The Raman spectra for the liquid, and the infrared spectra for both the gas and liquid have been obtained for CD 2 BrCl and a mixture of CH 2 BrCl, CD 2 BrCl, and CHDBrCl. The vibrational spectral data for CHDBrCl were deduced by eliminating the known bands of CH 2 BrCl and CD 2 BrCl from the data for the mixture. The assignments for CD 2 BrCl and CHDBrCl were confirmed by potential energy constant calculations. The observed values for the fundamentals of CD 2 BrCl in the Raman spectrum are: a ′—226, 574, 702, 922, 1042, and 2196; a ″—667, 809, and 2305. In the infrared, the values are: liquid—574, 703, 923, 1041, 2195, 668, 2302; gas—582, 717, 936, 1050, 2208, 811. The calculated wave numbers are: a ′—227, 564, 693, 926, 1055, 2161; a ″—672, 810, and 2250. For CHDBrCl, in the Raman spectrum the observed values for the fundamentals are: 228, 586, 707, 743, 867, 1179, 1264, 2246, and 3024; and in the infrared they are: gas—711, 746, 868, 1188; liquid—706, 743, 865, 1183, 1262, 2252, 3031. The calculated wave numbers are: 227, 578, 704, 740, 878, 1155, 1283, 2205, and 3020.