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Journal ArticleDOI

Acetyl halides—I

TL;DR: In this paper, the infrared and Raman spectra of acetyl chloride, d3 and d1 have been studied and a vibrational assignment has been made on the basis of an approximate normal-coordinate calculation with a Urey-Bradley field.
About: This article is published in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy.The article was published on 1961-01-01. It has received 57 citations till now. The article focuses on the topics: Acetyl chloride.
Citations
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Journal ArticleDOI
TL;DR: In this paper, the Urey-Bradley force field is not satisfactory unless it is augmented with some valence-force interaction constants, and the most probable force field indicates a decrease in the value of KCO in going from formaldehyde to acetaldehyde.
Abstract: Normal‐coordinate calculations have been carried out for the molecules acetone, acetone‐d6, acetaldehyde, acetaldehyde‐d4, acetaldehyde‐d1, formaldehyde, and formaldehyde‐d2. Infrared and Raman spectra for acetone, acetone‐d6, and acetaldehyde‐d4 were measured and assigned. Together with experimental data and assignments taken from the literature for the other molecules, these yield an almost complete set of fundamental frequencies.These frequencies were used to derive approximate force fields for these molecules and to investigate the transferability of the force constants. Calculations were carried out with both the Urey—Bradley force field (UBFF) and the valence‐force field (VFF) with selected interaction constants. The Urey—Bradley force field is not satisfactory unless it is augmented with some valence‐force interaction constants. In the valence‐force approximation it is not possible to make an unambiguous choice of the nondiagonal constants. However, a most probable force field is indicated, which on the one hand reproduces the experimental frequencies and on the other hand shows reasonable values for diagonal and nondiagonal force constant.The CO stretching constant, KCO, and the force constants around the CO group appear to be nontransferable among these molecules. The most probable force field indicates a decrease in the value of KCO in going from formaldehyde to acetaldehyde, to acetone. It is noted that the choice of interaction constants has a great influence on the values of the diagonal force constants and on the normal coordinates. Anharmonicity effects are also found to influence the values of the force constants and may affect the resulting conclusions.

190 citations

Journal ArticleDOI
TL;DR: In this article, the spectral properties of monomeric acetic acid [CH3COOH(D) and CD3COF] isolated in Ar and N2 matrices near 4°K are reported.
Abstract: Infrared spectra of monomeric acetic acids [CH3COOH(D) and CD3COOH(D)] isolated in Ar and N2 matrices near 4°K are reported. A large anharmonic potential‐energy contribution is evident from the observed isotopic frequency shifts. It is proposed that this arises primarily from the double‐minimum potential‐energy curve for tunneling of the H atom between O atoms via the COH angle bending coordinate. In all cases, important coupling between the COH angle bending and C–O stretching coordinates is observed, with a strong addition of CD3 (umbrella) angle deformation in the case of CD3COOH. Exceptional matrix effects are observed for the coupled vibrations of the –OH molecules. A complete assignment is proposed for these acetic acids on the basis of the new data. As additional supporting evidence, the spectrum of matrix‐isolated CH3COF and of acetic acid vapor at low pressure and long path length are reported.

81 citations

Journal ArticleDOI
TL;DR: In this paper, the infrared and Raman spectra of gaseous and solid propenoyl bromide, CH2 CHCBrO, have been recorded and qualitative depolarization values have been measured.
Abstract: The infrared and Raman (3500–30 cm−1) spectra of gaseous and solid propenoyl bromide, CH2 CHCBrO, have been recorded. The Raman spectrum of the liquid has been obtained and qualitative depolarization values have been measured. The fundamental asymmetric torsion for both the s‐trans and s‐cis conformers has been observed along with several hot transitions. From these transitions the potential function governing the internal rotation has been determined and the s‐trans to s‐cis barrier is 1861 cm−1 (5.32 kcal/mol), the trans conformer being more stable by 158±20 cm−1 (452±57 cal/mol). All normal modes have been assigned for the s‐trans conformer and many of those for the s‐cis conformer, based on band contours, depolarization values, and group frequencies. A normal coordinate calculation has been carried out by utilizing a modified valence force field to calculate the frequencies and the potential energy distribution for both conformers. Temperature studies of the Raman spectra of gaseous propenoyl fluoride...

81 citations

Journal ArticleDOI
TL;DR: In this paper, normal coordinate calculations have been carried out for methyl formate and formic acid on the basis of three different simplified harmonic force fields, and the infrared spectra of DCOOCD3 were obtained and the fundamental modes were assigned.

59 citations

Journal ArticleDOI
TL;DR: The Raman spectrum of liquid CF 3 COCl and the infrared spectra of the gas and the condensed solid have been studied, and fundamental frequencies assigned as discussed by the authors, and it was shown that the barrier to internal rotation in CF3 COCl is 400-500 cm −1, which would put the torsional vibration at 37-43 cm − 1, thus either the barrier is surprisingly low or the band is so weak that it has escaped detection.

54 citations

References
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Journal ArticleDOI
TL;DR: In this article, a general treatment of internal rotation is given for molecules whose moments of inertia for over-all rotation are independent of internal rotational coordinates, provided the potential energy can be expressed as a sum of terms of this type.
Abstract: A general treatment of internal rotation is given for molecules whose moments of inertia for over‐all rotation are independent of internal rotational coordinates. Tables are presented for the various thermodynamic functions which are accurate for molecules with one internal rotation and for the potential energy (V/2) (1 — cos nφ). The tables are shown to be a good approximation for molecules with several internal rotational coordinates, provided the potential energy can be expressed as a sum of terms of this type. Methods are suggested for treating problems where cross terms involving more than one internal coordinate are present in the potential energy. The energy level expressions are developed for the more general case with the potential energy expressed by a Fourier series. Although a few specific cases were worked out with different shape potential barriers, it appears that the simple form assumed above will be satisfactory for many purposes.

834 citations

Journal ArticleDOI
TL;DR: An algorithm for the systematic calculation of Urey-Bradley force constants has been programed for a digital computer (the Datatron 204) as mentioned in this paper, where the potential energy being transformed from Urey•Bradley space to internal coordinate space by a matrix Z. This same matrix is also used to transform the Jacobian of λ with respect to the force constants from internal coordinate to Urey • Bradley space.
Abstract: An algorithm for the systematic calculation of Urey‐Bradley force constants has been programed for a digital computer (the Datatron 204). The secular equation is set up and solved in internal coordinates, the potential energy being transformed from Urey‐Bradley space to internal‐coordinate space by a matrix Z. This same matrix is also used to transform the Jacobian of λ with respect to the force constants from internal‐coordinate to Urey‐Bradley space, thereby allowing the direct determination of Urey‐Bradley force constants. A method is described whereby the Z matrix and Wilson's G matrix may be set up by the computer from the geometrical parameters of the molecule.

188 citations

Journal ArticleDOI
TL;DR: In this paper, the Urey Bradley field for various chemical structures, stretching, bending and repulsive force constants were determined so as to give the best fit with the observed vibration frequencies.
Abstract: Assuming the Urey‐Bradley field for various chemical structures, stretching, bending and repulsive force constants were determined so as to give the best fit with the observed vibration frequencies The magnitude of these force constants, especially of repulsive constants, was discussed

139 citations

Journal ArticleDOI
TL;DR: The Raman spectra of liquid CH3CHO and CH3CDO were obtained photo-electrically and depolarization ratios measured in this paper, and a vibrational assign was also obtained.
Abstract: The Raman spectra of liquid CH3CHO and CH3CDO were obtained photo-electrically and depolarization ratios measured Infrared spectra of the vapors and solids were also obtained A vibrational assign

75 citations

Journal ArticleDOI
TL;DR: In this article, Urey-Bradley force constants have been fitted to the observed vibrational frequencies of COF2, COCl2, and COBr2 by the method described in the previous paper.
Abstract: Urey‐Bradley force constants have been fitted to the observed vibrational frequencies of COF2, COCl2, and COBr2 by the method described in the previous paper. These force constants have been used to calculate the frequencies of COClF, COBrF, and COBrCl. Normal coordinates and the potential energy distribution among the various Urey‐Bradley coordinates have also been calculated. It is found that, despite the fact that the carbonyl stretching frequencies fall over a range of 100 cm—1, the carbonyl stretching force constant is essentially the same for all molecules in the carbonyl halide series.

75 citations