Vibrational spectra of 3,5-dialkylbenzoic acid derivatives

A comparative vibrational spectra study of 2- and 4-CH₃, −NO₂ and Br-derivatives of some 3,5-dialkylbenzoic acids (R:-Me, −Et, −Prⁱ, −Bu^t) is carried out. We propose an explanation of its molecular structure.     

Vibrational spectra and molecular force field of N-methylpyridinium ion and some deuterated derivatives

The vibrational spectra of N-methylpyridinium iodide and three of its selectively deuterated derivatives have been recorded in the crystalline as w     

Vibrational spectra of diacetylene and its deuterated species

Infrared and Raman spectra of diacetylene-d₀, -d₁, and -d₂ have been recorded and a complete vibrational analysis is proposed for each of these three species.     

Vibrational analysis of tellurophene and its deuterated derivatives

The i.r. and Raman spectra of tellurophene, tellurophene-2-d₁, tellurophene-2-5-d₂, tellurophene-3-4-d₂, tellurophene-2-3-4-d₃ and tellurophene-2-3-4-5-d₄ have been studied. A vibrational assignment of the fundamental frequencies of all these molecules has been carried out on the basis of i.r. vapor band contours and depolarization states of Raman lines. Such an assignment conveniently fits the isotopic “sum” and “product” rules. A comparison of the vibrational behaviour of tellurophene and that of the other congeners is made and a rationalization of some frequency shifts is attempted.     

Vibrational spectra of hypophosphite ion and its deuterated species

The infrared and Raman spectra of the H₂PO₂^?, HDPO₂^? and D₂PO₂^? ions have been measured in aqueous solutions. The assignment of bands to the fundamental vibrations proposed is based on experimental tests, band polarisation measurements, application of all known isotopic rules and the construction and analysis of all the physically admissible assignments. The thermodynamic functions of the studied ions are calculated in the rigid rotator and harmonic vibrator approximation.     

Vibrational analysis of polyethylene terephthalate and its deuterated derivatives

The Vibrational analysis of polyethylene terephthalate, polyethylene-d₄ terephthalate, and polyethylene terephthalate-d₄ has been carried out using a valence force field calculated from the infrared and Raman spectra of a series of low molecular weight aromatic esters. The Raman spectra for polyethylene-d₄ terephthalate and polyethylene terephthalate-d₄ are presented and band assignments for these compounds and polyethylene terephthalate are discussed.     

Vibrational spectra of trinitromethane derivatives

Spectroscopic parameters of trinitromethane derivatives RC(NO₂)₃ (R = F, Cl, Br, I, NC, NF₂, N₃) were determined. Vibrational frequencies and modes were calculated and the assignment of experimental spectra was performed. Spectral features due to the mutual influence of the C(NO₂)₃ group and other atomic groups and particular atoms were revealed.     

Vibrational and conformational analysis of chloromethylacetate and some deuterated derivatives

The i.r. spectra of gaseous, amorphous and crystalline solid and the Raman spectra of liquid and amorphous solid chloromethylacetate, CH₃COOCH₂Cl, and three deuterated derivatives, CH₃COOCD₂Cl, CD₃COOCH₂Cl and CD₃COOCD₂Cl, were obtained and an assignment proposed. Only one conformer of CMA was found to be present in all phases. Band contour simulation of the i.r. vapour phase bands showed this to be the s-cis gauche conformer. This was confirmed by a study of the partially deuterated compound CD₃COOCDHCl, of which the separate transitions originating from the antiperiplanar and synclinal isolated CH stretches were observed in the i.r. spectra of the vapour and crystalline solid and in the Raman spectrum of the vapour.     

Vibrational spectra and normal coordinate analysis of p-cresol and its deuterated analogs

I.r. and Raman spectra of p-cresol and its seven deuterated analogs were investigated in dilute solutions of hydrophobic solvents. Assignments of the observed i.r. and Raman bands were made on the basis of isotopic frequency shifts, Raman polarization properties, i.r. intensifies and normal coordinate calculations. The calculated normal frequencies are in good agreement with the experimental ones: the average error below 1700 cm⁻¹ is 3.8 cm⁻¹ for 164 in-plane vibrations and 3.3 cm⁻¹ for 59 out-of-plane vibrations. The calculated vibrational modes may be useful in analysing the vibrational spectra of tyrosine. It is suggested that several doublets due to Fermi resonance and a trio of Raman bands in the 1260-1160 cm⁻¹ region are potential probes for the micro-environments of tyrosine side chains in proteins.     

Vibrational spectra and structures of 1,2,4-triazole derivatives

The frequencies and forms of the normal vibrations of a number of azido derivatives of 1,2,4-triazole [3-bromo-5-azido-(I), 1-methyl-3razido-(II), and 3-azido-5-nitro-1,2,4-triazole (III)] were calculated. The inverse spectral problem for the parameters of the azido group was solved by the method of least squares. A similar method was used to calculate the potential energy constants of the triazole ring with the aid of data on the force fields of the previously investigated nitrotriazoles. It is shown that the introduction of electron-donor or electron-acceptor substituents in the triazole ring does not affect the force constants of the CN and NN bonds of the azido group. Transmission of the electronic effects in the ring as a function of the nature and position of the substituent was investigated.See [1] for communication V.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 839–842, June, 1977.     

Vibrational spectra and structure of 1,2,4-triazole derivatives

The frequencies and forms of the normal vibrations of the anions of 1,2,4-triazole and 3-nitro-, 3-nitro-5-methyl-, and 3,5-dinitro-1,2,4-triazoles were calculated. The potential energy constants were calculated by solution of the reciprocal spectral problem, and the frequencies in the experimental spectra were assigned to the fundamental types of normal vibrations. It is shown that the nitro groups in the 3 and 5 positions in the anions of the triazoles are located in the plane of the triazole ring. The coordination of the metal in crystalline salts of nitrotriazoles was studied by the methods of vibrational spectroscopy, and an assumption is stated that the most probable position of the metal is near the oxygen atoms of the nitro group along the Me-O-N line. As a result of a theoretical analysis of the vibrational spectra of the anions it was ascertained that equalization of the lengths of the ring CN bonds does not occur during ionization of the covalent triazoles. Calculations by the MO LCAO SCF method are in agreement with the data from vibrational spectroscopy.See [1] for communication III.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1423–1431, October, 1973.     

Vibrational spectra of 1,3,5-hexatriene and methylated derivatives

The ground state vibrational spectra of E-hexatriene, Z-hexatriene, E,E-heptatriene, E,E,E-octatriene, and E-2,5-dimethyl-hexatriene are reported. For E- and Z-hexatriene complete vibrational assignments, and for heptatriene, octatriene, and dimethyl-hexatriene near-complete assignments are obtained. The effects of terminal and lateral methyl-substitution are compared.     

Vibrational spectra and structure of 1,2,4-triazole derivatives

From an analysis of the IR and Raman spectra and a calculation of the frequencies and forms of the normal vibrations of the nitrotriazoles, conclusions have been drawn on the structure of 3,5-dinitro-1,2,4-triazole and 1-methyl-3,5-dinitro-1,2,4-triazole. The nitro group in position 3 of the triazole ring is located in the plane of the molecule, and that in position 5 is rotated about the CN bond. The spatial nonequivalence of the nitro groups leads to the splitting of the absorption bands in the IR spectra that are characteristic for the anti- and synphase vibrations of the nitro groups.For Communication (II), see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1194–1198, September, 1973.     

Vibrational spectra and structure of 1,2,4-triazole derivatives

The frequencies and forms of the normal vibrations of 3-nitro-1,2,4-triazole, its 1-deuteroand 1-methyl derivatives, and 1-methyl-3-nitro-5-chloro(bromo)-1,2,4-triazole, which are classified as having C_S group symmetry, were calculated. The potential energy constants were refined by solution of the reciprocal spectral problem, and the frequencies in the experimental spectra were assigned to the principal types of vibrations.See [1] for communication I.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 707–712, May, 1973.     

Vibrational spectra and structures of 1,2,4-triazole derivatives

The vibrational spectra of 1,2,4-triazole and its 3-chloro and 3-bromo derivatives were calculated for the C_S point symmetry group. The potential energy constants were computed, and it is shown that the force field of the triazole ring has the additivity property; i.e., it remains practically constant when electron-acceptor groups such as chlorine and bromine are introduced into the 3 position. The force constants of interaction of the valence and angular coordinates of the ring have high values; this is a characteristic of the considerable rigidity of the triazole ring. The fundamental frequencies in the experimental spectra were assigned on the basis of an analysis of the calculated forms of the normal vibrations.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1567–1570, November, 1972.     

Vibrational spectra and structure of 1,2,4-trlazole derivatives

The frequencies and forms of the normal vibrations of 3-azido- and 3-azido-5-methyl-1,2,4-triazoles and their 1-deutero-substituted derivatives were calculated, the effect of the geometrical parameters of 3-azido-1,2,4-triazole on the vibrational spectra was investigated, and the most probable three-dimensional model of the molecule was selected. The solution of the inverse spectral problem was effected by the method of least squares, and the potential energy constants of the azidotriazoles were calculated. It is shown that the force constants of the azido group increase and the elastic constants of the ring decrease when an azido group is introduced into the 1,2,4-triazole molecule. The frequencies in the experimental spectra were assigned to the principal types of normal vibrations.     

Vibrational spectra of tetramethyleyclobutane-1-one-3-thione and the fully deuterated derivative

Raman and i.r. spectra of tetramethylcyclobutane-1-one-3-thione (TMCBOT) and the fully deuterated derivative TMCBOT-_d¹² have been recorded. A fairly complete set of vibrational frequencies and assignments are given for the two molecules. The CO stretching mode was observed as a very strong Fermi doublet in the infrared spectrum of TMCBOT at 1811/1782 cm⁻¹. For TMCBOT-d₁₂ a similar doublet was observed at 1808/1775 cm⁻¹. The CS stretching mode was assigned to bands at 1303 cm⁻¹ for TMCBOT and 1307 cm⁻¹ for the deuterated molecule.