scholarly journals Intrachain Force Field and Normal Vibrations of Polyethylene Glycol

1968 ◽  
Vol 41 (8) ◽  
pp. 1798-1808 ◽  
Author(s):  
Hiroatsu Matsuura ◽  
Tatsuo Miyazawa
Keyword(s):  
Polyethylene Glycol ◽  
Force Field ◽  
Normal Vibrations

scholarly journals The absorption spectra and photochemistry of poly­atomic molecules containing alkyl radicals - V—Vibration frequencies and structure

1937 ◽  
Vol 160 (903) ◽  
pp. 539-562 ◽  
Keyword(s):  
Force Field ◽  
Degrees Of Freedom ◽  
A Priori ◽  
Ultra Violet ◽  
Force Constants ◽  
Molecular Structures ◽  
Vibration Frequencies ◽  
Complex Molecules ◽  
Normal Vibrations ◽  
Alkyl Radicals

One of the most important properties of a molecule is its ability to vibrate. A complete knowledge of the normal vibrations of a polyatomic molecule not only provides valuable indications of its structure, but also may eventually be of value in elucidating the mechanism of reactions in which the molecule takes part, for it is largely among such vibrational degrees of freedom that energies of activation may be stored. The vibration frequencies of molecules are usually determined by spectroscopic methods, and considerations based on known Raman, infra-red, or ultra-violet spectral data often make it possible not only to determine their magnitudes but also to assign observed vibration frequencies to the specific vibrational types. It is, however, also possible, provided some knowledge of the force field existing in a molecule is assumed, to calculate the normal vibration frequencies of molecules, and at the same time to deduce the directions of the atomic amplitudes. Such calculations (Bjerrum 1914; Dennison 1926; Yates 1931; Radakowicz 1930, 1932; Lechner 1932; Howard and Wilson 1934; Sutherland 1936; Howard 1935; Sutherland and Dennison 1935) often serve to test previous empirical assignments, and may also help in deciding or confirming the molecular structures. If the vibration frequencies of a molecule are known from experimental data, both in regard to magnitude and assignment, we can, conversely, calculate the properties of the force field existing in the molecule, this being customarily expressed by the magnitudes of the various “force constants”. We might then, a priori at least, expect to be able to use these deduced force constants in calculating the vibration frequencies of more complex molecules of the same type and involving similar linkages. An example of this procedure is discussed in the present paper, and the extent of its limitations is revealed.

Transfert du champ de forces de l'isothiazole: étude des vibrations moleculaires des dérivés de l'isothiazole monosubstitués en position 3, 4 ou 5

1976 ◽  
Vol 54 (24) ◽  
pp. 3850-3856 ◽  
Author(s):  
Gilbert Mille ◽  
Jacques Chouteau ◽  
Thierry Avignon ◽  
Luc Bouscasse
Keyword(s):  
Experimental Data ◽  
Force Field ◽  
Normal Vibrations ◽  
Valence Force ◽  
Valence Force Field

The study of normal vibrations of 3-, 4-, or 5-monosubstituted isothiazole derivatives, assuming transferability of the valence force field of isothiazole, gives results which agree with the experimental data and which permit the assignment of the various vibrations.

Valence Force Constants and Normal Vibrations of Methanol

1970 ◽  
Vol 25 (11) ◽  
pp. 1729-1731 ◽  
Author(s):  
A. Timidei ◽  
G. Zerbi
Keyword(s):  
Force Field ◽  
Molecular Spectroscopy ◽  
Harmonic Approximation ◽  
Force Constants ◽  
Least Square ◽  
Vibrational Modes ◽  
Normal Vibrations ◽  
Valence Force ◽  
Valence Force Field

Abstract The possibility of reproducing the normal vibrations of methanol, CH3OH, and its deutero-derivatives CH3OD, CD3OH, CD3OD using a valence force field has been critically analyzed. A 13 parameter valence force field has been determined by least square calculations. The meaning of the obtained numbers and their validity in molecular spectroscopy are discussed and compared with the information already available in the literature. It is concluded that the vibrational modes of this molecule are fairly well known within the harmonic approximation.

scholarly journals The vibration spectrum and molecular configuration of 1:4-dioxane

1947 ◽  
Vol 190 (1023) ◽  
pp. 562-574 ◽  
Keyword(s):  
Raman Spectrum ◽  
Force Field ◽  
Vibration Spectrum ◽  
Vibration Frequencies ◽  
Molecular Configuration ◽  
Normal Vibrations ◽  
The Third ◽  
Symmetry Properties ◽  
Infra Red ◽  
Low Symmetry

The symmetry properties and selection rules for the normal vibrations of 1:4-dioxane have been derived for all possible symmetries of the molecule. The numbers of frequencies observed in the infra-red spectrum of the vapour and Raman spectrum of the liquid are shown to be inconsistent with structures of low symmetry. While the number of observed Raman frequencies do not distinguish between the ‘chair’ and planar configurations, the number of observed infra-red frequencies slightly favours the ‘chair’ structure. The twelve vibration frequencies of the ring have been calculated for the ‘chair’ structure using a simple valency force field with four force constants. Seven of the calculated frequencies agree with the observed frequencies to within 1%, and two frequencies agree to within 3 to 4%. Of the three remaining frequencies, two are active in the infra-red spectrum but are too low to be observed with prism spectrometers, while the third is active in the Raman spectrum but has not been experimentally observed. These three frequencies, however, agree satisfactorily with the corresponding assignments for cyclohexane. The stretching constants of the C-C and C-O bonds, viz. 3.7 x 10 5 and 4.45 x 10 5 dynes/cm., were found to be the same as for cyclohexane and dimethyl ether respectively.

Sign in / Sign up

Export Citation Format

Share Document