Sándor Holly

Vibrational spectra of monothiocarbamates-II. IR and Raman spectra, vibrational assignment, conformational analysis and ab initio calculations of S-methyl-N, N-dimethylthiocarbamate

Abstract The IR (3200–30 cm−1) spectra have been recorded for S-methyl-N,N-dimefhylthiocarbamate, (CH3)2NC(O)SCH3, and its isotopomers, S-d3, N-d6 and N-d9, for the gas and liquid. Additionally, the Raman spectra (3200–10 cm−1) for the solid and liquid, with qualitative depolarization ratios, have been obtained for all the isotopes. These data are interpreted on the basis that the s-cis conformer (the S-methyl group oriented eis to the carbonyl group) with Cs symmetry is the only form existing in all three phases for this molecule. A complete vibrational assignment proposed for the -d0 molecule is facilitated by the availability of spectral data for five different isotopomers. A normal coordinate analysis has been carried out utilizing ab initio calculations with the 3–21G* basis set. The potential energy distributions and ab initio calculated frequencies have allowed a clarification of some of the corresponding results obtained from experiment. Structural optimizations and potential surface scan have also been carried out by ab initio calculations with the 3–21G* basis set. These results are compared with some previous studies on this molecule as well as on similar molecules.

A comparative study on the vibrational spectroscopy of pyridazine, pyrimidine and pyrazine

Abstract In this work, the authors deal with the vibrational spectroscopy of the three diazine parent compounds, i.e. that of pyridazine, pyrimidine and pyrazine. Infrared spectra were recorded in vapour and condensed phases, and Raman spectra were measured in condensed phase using both parallel and perpendicular polarization of light. The vibrational fundamental frequencies were calculated applying ab initio quantum-chemical methods: Moller–Plesset perturbation and local density functional methods. The results of the calculations were applied to the assignment of the vibrational fundamentals and the measured fundamental frequencies were used to refine the vibrational force constants. The main deviations between the recalculated and the measured frequencies are about 2.5% or smaller.

Ester type banana-shaped liquid crystalline monomers: synthesis and physical properties

New ester-type banana (bent-shaped) monomers, 1,3-phenylene bis[4′-(alken-1-yloxy)-biphenyl-4-carboxylate]s Ia–Vb, with different substituent(s) on the central phenyl ring (H, CH3, Cl or NO2) and alkenyl tails in the side arms (decenyl or undecenyl) were prepared. The analogues IIIa–IVb with 4-chloro- or 4,6-dichloro-substituents exhibited a nematic phase, while Va,Vb with 2-nitro-substituent showed a B7 phase at relatively low temperature. All the compounds were stable, no degradation or polymerization was observed under applied electric fields or heat treatments. Electro-hydrodynamic instabilities were observed in the nematic phase of each sample. In the B7 phase of Vb there was an electro-optical switching in the range 112–114.5 °C with a switching time of about 150 µs at 20 V µm−1 field. At lower temperatures no electro-optical switching occurred, but a ferroelectric-type spontaneous polarization of 22 nC cm−2 could be detected. The bend angle was calculated by the semiempirical CAChe/MOPAC/PM5 method.

INVESTIGATION OF THE MORPHOLOGICAL COMPOSITION OF CIMETIDINE BY FT-RAMAN SPECTROSCOPY

The Raman spectra of six polymorphic crystal forms of N-cyano-N′-methyl-N″-{2-[(5-methyl-1H-imidazol-4-yl)methylthio]ethyl}-guanidine (Cimetidine) have been studied to investigate the possibility of quantitative analysis of polymorphic mixtures. Characteristic Raman bands of the various polymorphs have been found, some of which proved to be appropriate for quantitative analysis. The applicability of various mathematical techniques has been investigated, of which partial least-squares (PLS) has been found to be the best.

Vibrational spectroscopic and quantum chemical study of the chlorine substitution of pyrazine

Abstract Vibrational spectroscopy of pyrazine and its two chlorine derivatives, the 2-chloropyrazine and the 2,6-dichloropyrazine have been investigated. The substituent effect and the chlorine isotopic effect were investigated, too. Infrared spectra were recorded in condensed and in vapour (pyrazine, 2-chloropyrazine) phase, Raman spectra in condensed one. In the case of pyrazine and 2-chloropyrazine the spectra were excited both with parallel and perpendicular polarised light. The optimised geometry and the force field of the investigated molecules were calculated using the density functional theory with the Becke3P86 functional and the 6-311G** basis set. The results of the calculations were applied to the assignment of the vibrational fundamentals. The measured spectral data were used to refine the vibrational force constants. The intermolecular interactions of the compounds shifted the fundamental frequencies of the isolated molecules.

The Effect of HCl on the Copper(II) Chloride/Pyridine/Water System: Synthesis, Properties and Crystal Structure of [(pyH)2CuCl4] and [(pyH)2Cu3Cl8(H2O)2]n

Bis(pyridinium) tetrachlorocuprate monomer 1 and bis(pyridinium) octachlorodiaquatricuprate polymer 2 were synthesized and their crystal structures were determined. Both complexes contain pyridinium cations with bifurcated H-bridges. These H-bridges stabilize the monomeric structure of the tetrachlorocuprate anion together with the steric demand of the relatively large pyridinium ions in the crystal lattice of 1. Conversely, at the lower pyridinium ion:copper(II) ratio of 2, the bifurcated hydrogen bonds reduce the electron density on the chloride ions in such a way that the electron repulsion decreases and coordination spheres with more ligand interactions develop. Obviously, water may be a successful competitor for ligand sites in 2 as well. The octahedral and square-pyramidal structural units condense into polymeric chains which are stabilized by the interchain hydrogen bond networks of the water molecules. The structure motif of SP-5-[OC-6-SP-5-SP-5]-OC-6 (−CuCl5-[CuCl4(OH2)2-CuCl5CuCl5]-CuCl4(OH2)2-) were observed in 2, and the two neighboring square-pyramidal units were found to be localized in a transoid position. The IR and ESR spectroscopical characterization of complexes was also performed.

Metabolism of mesocarb in the rat

1. Rats treated orally with [14C]mesocarb (I; 3-(1-methyl-2-phenyl[2-(14C]ethyl)-N-(phenylaminocarbonyl)sydnone imine) (50 mg/kg) excrete 35% of the radioactivity in 24 h urine and 51% in 48 h urine. 2. Only traces of unchanged drug were found in urine. Hydroxy-mesocarb (II), dihydroxy-mesocarb (III), amphetamine (VII) and the conjugates of II and III account for 86% of the urinary radioactivity. 3. Cannulated male rats excrete about 40% of the radioactivity in 30 h in bile, mainly as conjugates of II and III.

A chiral side-chain polymer with layered structure

Abstract A chiral side-chain polymer was synthesized and its chemical structure was proved by infrared spectroscopy. According to the X-ray diffraction studies the polymer exhibited smectic type ordering however it did not show any birefringence macroscopically.

Some characteristic vibration patterns of the organic nitro group

Abstract It has been established that satellite bands appear in the antisymmetric stretching vibration band of the NO2 group in the liquid state. This is interpreted by v—v transitions of the torsional oscillation between the nitro and methyl group, and this suggested that in the excited state of the antisymmetric NO2 stretching vibration, the frequency of the torsional oscillation changes. On the basis of Reinerts microwave measurement data it was shown that nitrobenzene is a planar molecule, and that the difference between the moments of inertia can be worked out quantitatively from the mean square of the zero state vibration elongations. Further calculation also confirmed assumptions about the appropriate frequency of the torsional oscillation of the nitro group.

Infrared and Raman spectra of cis-stilbene and its deuterated isotopomers

Abstract The vibrational analysis of cis -stilbene in the ground electronic state based on the infrared and Raman spectra of a series of its isotopomers and scaled semiempirical AM1 calculations is reported. The C α C α stretching, all the four C α H deformations and the C α C α torsion are described. A comparison with trans -stilbene shows a much lesser degree of couplings between olefinic and phenyl vibrations in cis -stilbene.