D.N. Sathyanarayana

Raman and polarized infrared spectra of pyridine-2-thione

Polarized i.r. spectra of oriented polycrystals and the i.r. and Raman spectra of polycrystalline samples of pyridine-2-thione have been obtained. The Raman spectra of a solution of pyridine-2-thione has also been measured and the polarization of many lines determined. The i.r. spectra of S-methyl and N-deuterated compounds have also been investigated. A complete assignment of all the observed peaks has been possible. The results are correlated with the assignments available for related systems.

Molecular vibrations of pyridine-2-thione and pyrimidine-2-thione

Molecular vibrational analyses of two biochemically important molecules, namely pyridine-2-thione and pyrimidine-2-thione, have been made for all the fundamentals employing the Urey-Bradley potential function supplemented with valence force function for the out-of-plane vibrations. The spectra of N-deuterated molecules have also been utilized. The results of the vibrational analyses are discussed in relation to the assignments in structurally related molecules to note the consistency in the assignments

Ab initio study of the force field, geometry and vibrational assignment of urea

The optimized goemetry and the complete harmonic force field or urea have been calculated at the ab initio Hartree—Fock level using 3–21G as well as 6–31G basis sets. On this basis, a thorough discussion is presented on the previously observed infrared spectra of urea and urea-

A theoretical study of the vibrational spectra, geometry and force field of thiourea

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Vibrational spectra of imidazoline-2-thione and imidazoline-2-one

in an argon matrix. The accuracy of the force constants was tested by calculating the

1H and 13C NMR study of pyridylamides and thionamides

^{15}N

Vibrational assignments of five-membered heterocyclic compounds. Normal vibrations of oxazolidine-2-one and -2-thione

-isotopic shifts for the vibrational frequencies of urea and urea-

Molecular conformation of 1,3-pyridylphenylureas by 1H and 13C NMR study

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Conformation of some N,N′-arylalkyl thioureas by 1H-NMR and infrared spectral analysis

, and the agreement between the calculated and observed shifts is remarkably good. The calculated force fields are utilized to critically examine the published experimental assignments of urea and some revisions are suggested. Evidence is presented for large frequency shifts in carbonyl and hydrogen-involving vibrations due to intermolecular hydrogen bonding in the solid state. The theoretical geometry and the ab initio force constants of urea are compared with the results of the experimental study. The theoretical infrared and Raman intensities of the normal modes together with qualitative experimental band intensities are presented. The predicted relative intensities compared well qualitatively with experiment for the matrix isolated species.

Proton NMR and infrared investigations of secondary dithiocarbamate ester: molecular conformation and vibrational assignment of S-methyl N-methyl dithiocarbamate

A theoretical force field for the molecular vibrations of thiourea has been determined from ab initio calculations at the Hartree-Fock level using the 3-21G* basis set. The reliability of the force field is analyzed by calculating the vibrational frequencies for the deuterated and