Vibrational spectra of thiuram sulfides: Normal coordinate analysis of tetramethylthiuram mono-, di-, and tetrasulfides

The normal coordinate analyses of tetramethylthiuram mono-, di-, and tetrasulfides have been carried out by utilizing vibrational energies obtained from infrared and Raman spectroscopic data reported here. The C?S vibration is demonstrated to be highly coupled and to contribute to frequencies in the 850–1000 cm^?1 region, but can be identified based on the strong Raman intensity. The results are useful in interpreting the spectra of these complex vulcanizing agents.     

Vibrational spectra and stereochemistry of mono- and polysaccharides

A comparative study of the IR and Raman spectra of D-glucose anomers is reported. The spectra were found to differ between the anomers, despite the absence of symmetry elements in the anomer molecules. The results of theoretical calculations are systematized; it was found that the skeletal CiOi or CiO(i+1) (i=1, 2, 3, 4, 5) bond is characterized by a specific set of frequencies of normal vibrations, which have predominant contributions from the vibrations of atomic groups involving these bonds to the potential energy distribution (PED). The frequencies of normal vibrations with the major contribution to PED from CO and CC bonds are well separated and differ between the D-glucose anomers. The C5C6 bond has the greatest number of normal vibrations with predominant contributions to PED. Model calculations of vibrational spectra are reported for D-glucose anomers with modified (β→α and α→β) conformations of the CH₂OH group. B. I. Stepanov Institute of Physics, Belarus Academy of Sciences. Institute of Low Temperatures and Structural Studies, Polish Academy of Sciences, Wroclaw. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 322–329, March–April, 1995. Translated by L. Smolina     

13C NMR spectra and structure of mono-, di- and trimethoxyphenylethylamines and amphetamines

Carbon-13 and proton chemical shifts of mono-, di- and trimethoxylated phenylethylamines (PEAs) and their hydrochlorides were determined and the signals were assigned and are reported. The data are interpreted to indicate that the side-chains of PEA derivatives and amphetamine salts have the amino and aromatic moieties predominantly trans (antiperiplanar), that ‘sandwiched’ OCH₃ groups and side-chains are forced out of the ring plane and that planar ortho-OCH₃ groups have their electron lone pairs oriented toward the side-chain and partially stabilize gauche rotamers. It is suggested that the location and density of electronic charges just outside the aromatic ring will significantly affect interactions with putative receptors.     

Thermal analysis of ammonium,mono-, di- and triethanolammonium alginates

Thermal behaviour of ammonium (NH₄alg), mono- (MEAalg), di- (DEAalg) and triethanolammonium (TEAalg) salts of alginic acid (Halg) was investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC). Salts were prepared by the direct reaction of alginic acid with the ammonium hydroxide and with the respective ethanolamines. After preparation the compounds were lyophilized during 24 h and characterized by FTIR spectroscopy and elemental analysis (C, H and N). Under air the compounds exhibited three successive thermal decomposition steps: dehydration, decomposition of the polymeric matrix and finally, burning of carbonaceous residue. Under nitrogen two steps (dehydration and decomposition) were observed. The stability order of this series of compounds was: TEAalg this series of compounds was: TEAalg<DEAalg<NH₄alg<Halg≈MEAalg. DSC curves between –50 and 150°C did not show any thermal events suggesting that after lyophilization probably non-freezing type water is present in the system.     

Facile synthesis of mono-, di-, and trisubstituted alpha-unbranched hydrazines

Methods for the alkylation of di-tert-butyl hydrazine-1,2-dicarboxylate were investigated. It was found that under mild conditions mono- or di-substituted hydrazine derivatives were obtained in good to excellent yield. Furthermore, it was shown that one of the two Boc-groups of the disubstituted derivatives was selectively removed by heating, leading to precursors for trisubstituted hydrazines.     

Synthesis of mono-, di- and trisulfated Lewis x trisaccharides

3′-Sulfated and 3′,6′-disulfated Lewis x trisaccharides have been prepared through selective sulfation of methyl 2-acetamido-6-O-benzyl-2-deoxy-4-O-β-D-galactopyranosyl-3-O-(2,3,4-tri-O-benzyl-α-L-fucopyranosyl)-β-D-glucopyranoside, followed by catalytic hydrogenolysis. In a similar manner, 3′,6-disulfated and 3′,6,6′-trisulfated Lewis x trisaccharides have been selectively obtained from methyl 2-acetamido-2-deoxy-4-O-β-D-galactopyranosyl-3-O-(2,3,4-tri-O-benzyl-α-L-fucopyranosyl)-β-D-glucopyranoside.     

Vibrational spectra and stereochemistry of mono- and polysaccharides. IV. α-methyl-d-glucoside, α-methyl-d-galactopyranoside,and α-methyl-d-mannopyranoside

The IR and Raman spectra of α-methyl-D-glucoside (αMDG), α-methyl-D-galactoside (αMDGal), and α-methyl-D-mannoside (αMDM) are compared. The main distinctions between these spectra have been interpreted using experimental and theoretical data on the frequencies and modes of normal vibrations and on the potential energy distributions over particular bonds and atomic groups of the substances under investigation. Spectral characteristics that are determined by different configurations of C−O (CH) groups attached to C2 and C4 atoms and different conformations of C6H₂O6H fragments have been revealed. It has been established that replacement of hydroxyls at C1 with methoxy groups significantly increases the number of frequencies of normal vibrations that are localized mostly in the C1C2 bonds (particularly in αMDGal). For the αMDGal molecules with axial C4O4 groups, the number of frequencies of normal vibrations that show predominant contributions of these groups of PED is smaller. For the αMDM molecules, in which the conformation of CH₂OH groups (with respect to rotation around the C5C6 bonds) differs from that in αMDG and αMDGal molecules, most vibrations are localized in the C6O6 bonds rather than in the C5O5 bonds. This fact is very important in correlating the vibrational spectra and structural properties of mono- and polysaccharides. B.I. Stepanov Institute of Physics, Belarus Academy of Sciences. V. Tshebyatoski Institute of Low Temperatures and Structural Studies, Polish Academy of Sciences. Translated fromZhurmal Struktumoi Khimii, Vol. 36, No. 3, pp. 456–466, May–June, 1995. Translated by I. Izvekova     

Synthesis of new chiral mono-, di-, tri-, and tetraalkylglycolurils

Two general procedures were developed for the synthesis of chiral N-mono-, N, N′-di-, N, N′ N″-tri-, and N, N′, N″, N′″-tetraalkylglycolurils based on the reactions of 4,5-dihydroxy-imidazolidin-2-ones or glyoxal with one or two moles of alkylureas, respectively, by acid catalysis. The reactions of N-monoalkyl- and N, N′-dialkylureas with glyoxal proceed regioselectively. The mechanism of these reactions was suggested and partly confirmed by quantum-chemical calculations and experimental data. The enantiomeric separation of some chiral glycolurils by chiral-phase HPLC was carried out for the first time.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 680–692, March, 2005.     

Vibrational spectra and stereochemistry of mono- and polysaccharides. III. β-methyl-d-glucoside, α-methyl-d-glucoside,and β-methyl-d-xyloside

The IR and Raman spectra of β- and α-methyl-D-glucosides and β-methyl-D-xyloside are compared. Experimental data are correlated with theoretical calculations of the frequencies of normal vibrations. Predominant contributions (20% and more) of particular CiOi and CiC(i+1) bonds to the potential energy distribution of normal vibrations (i.e., localization of vibrations on these bonds, which form skeletons of monosaccharide molecules) are estimated. This approach is used to interpret the main distinctions between the IR and Raman spectra of the test compounds. The use of vibrational spectra in selective analysis of certain functional groups is discussed. It is shown that replacing the hydroxyl group at C1 has a specific effect on the predominant localization of vibrational modes in particular skeletal bonds (mainly in C1O1) of the monosaccharide molecules. B. I. Stepanov Institute of Physics, Belarus Academy of Sciences. V. Tshebyatovski Institute of Low Temperatures and Structural Studies, Polish Academy of Sciences. Translated fromZhurmal Strukturnoi Khimii, Vol. 36, No. 3, pp. 443–455. May–June, 1995. Translated by I. Izvekova.     

The Soret effect of mono-, di- and tri-glycols in ethanol

We employed thermal diffusion forced Rayleigh scattering (TDFRS) to investigate the chain length dependence of the thermal diffusion behavior of short glycols in ethanol. We studied three glycols, monoethylenglycol (MEG), diethylenglycol (DEG) and triethylenglycol (TEG), in an ethanol solution. In contrast to the polymer polyethylenglycol, the shorter glycols used within the framework of this study are completely soluble in ethanol, at least for low molar fractions. In order to guarantee a good solubility of the glycols, the measurements were limited to molar fractions of 10% and 20%. As the different glycols only differ by their chain length it will be possible to deduce its influence on the thermal diffusion properties. Due to the fairly short persistence length of the glycols, D(T) reaches already for the dimer a plateau value. This finding agrees with simulation results. Furthermore, the thermal expansion and the kinematic viscosity are measured to investigate if empirical correlations seen for other systems could be confirmed.     

Partition chromatography of mono-, di- and trisaccharides on ion-exchange resins

Summary Complicated mixtures of mono-, di- and trisaccharides were separated on ion-exchange resins by partition chromatography using a mixture of water and ethanol as eluant. Among the resins studied, a cation exchanger in the lithium form gave the best separations of most common disaccharides. Mixtures containing several monosaccharides and some higher saccharides are better resolved when an anion exchanger in the sulfate form is employed. With some complex mixtures of mono-, di- and trisaccharides some overlapping occurred with both types of resin. A complete resolution of such mixtures can be achieved if fractions containing overlapping compounds are rechromatographed on the other resin form.

---

Zusammenfassung Mischungen von Mono-, Di- und Trisacchariden wurden durch. Verteilungs-Chromatographie an Ionenaustauscherharzen getrennt, wobei eine Wasser-Äthanolmischung als Eluierungsmittel diente. Die besten Ergebnisse bei der Trennung der gebräuchlichsten Disaccharide wurden mit einem Kationenaustauscher in der Li-Form erhalten. Für Mischungen, die mehrere Monosaccharide sowie höhere Saccharide enthielten, war ein Anionenaustauscher in der Sulfatform vorteilhafter. Bei einigen Mischungen von Mono-, Di- und Trisacchariden traten bei beiden Austauscherarten Überlappungen auf. Eine vollständige Trennung solcher Gemische konnte durch nochmalige Chromatographie der entsprechenden Fraktionen mit Hilfe des jeweils anderen Harzes erreicht werden.

     

Kinetic thermal analytical study of saturated mono-, di- and tri-glycerides

A thermal degradation study using TG–DTG thermogravimetry was performed on three saturated fatty acids esterified with glycerol (i.e. glyceryl-tristearate (C₁₈), -tripalmitate (C₁₆) and -trimyristate (C₁₄)) at different heating rates. In addition, thermogravimetry (TG) and derivative thermogravimetry (DTG) of glyceryl di-stearate and glyceryl mono-stearate were also carried out at different heating rates. A deconvolution procedure applied to the first process and overlapping at least two steps between about 200 and 350 °C, enabled the activation energy of decomposition to be determined both by the Kissinger and the Ozawa–Flynn–Wall isoconversional methods for the deconvoluted steps of the above-mentioned fatty acids.     

Surface characterizations of mono-, di-, and tri-aminosilane treated glass substrates

The surface properties and structure of mono-, di-, and tri-aminosilane treated glass surfaces were investigated using surface analytical techniques including X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, atomic force microscopy (AFM), and streaming potential. An optimized dip-coating process was demonstrated to produce roughly silane monolayer coverage on the glass surface. The surface charge measurements indicated that aminosilanization converts the glass surface from negative to positive potentials at neutral pH values. Higher positive streaming potential was observed for tri-compared with mono- and di-aminosilane treated glass surfaces. For all aminosilane treated glass samples, the high-resolution N 1s XPS spectra indicated a preferential orientation of the protonated amino-groups towards the glass surface whereas the free amino groups were protruding outward. This study aimed to obtain uniform, reproducibly thin, strongly adhering, internally cross-linked, and high positively charged aminosilane-coated glass surfaces for the attachment of DNA fragments used in microarraying experiments.     

Vibrational and NMR spectra of mono- and di-chlorothiolacetic acids in relation to rotational isomerism and hydrogen bonding

The vibrational spectra of mono- and di-chlorothiolacetic acids have been measured in liquid and gaseous states and solutions, and vibrational assignments have been proposed. The experimental material shows that these molecules are present as a mixture of two rotational isomers. The energy of the two isomers in the liquid state is almost the same.     

Analysis of mono-, di-, and triglycerides by capillary supercritical fluid chromatography

The separation of mixed mono-, di-, and triglycerides by capillary supercritical fluid chromatography is described. The separations were performed at low operating temperatures, using a carbon dioxide mobile phase, a conventional flame ionization detector, and two different stationary phases, DB-5 (95% dimethyl-(5%)-diphenylpolysiloxane) and DB-225 (50% cyanopropyl-methyl-(50%)-methylphenylpolysiloxane). Because the separations were performed at low operating temperatures, no thermal degradation of the glycerides was observed. Even under these mild operating conditions, trinervonin, a triglyceride having a molecular weight over 1100 amu, was readily eluted. When rapid pressure programming of the carbon dioxide mobile phase was employed, trinervonin was eluted in less than two minutes. On DB-5, the mono-, di-, and triglycerides eluted in order of increasing molecular weight. A graph of t′_r (on DB-5) versus molecular weight is linear. When DB-225 was used as the stationary phase, triglycerides eluted in the order of increasing unsaturation. Thus, the order of elution on DB-225 was tristearin, triolein, trilinolein, and trilinolenin.     

Complexation of zinc octaalkylporphyrin with mono-, di-, and triethylenediamines in toluene

The complexation of zinc octaalkylporphyrin with mono-, di-, and triethylenediamines in toluene was studied by spectrophotometry using the molar ratio method and by ¹H NMR. The effect of the structure of the two-center organic base on the formation of 1 : 1 or 2 : 1 metal porphyrin-ligand complex was established. The stability constants of the resulting complexes were calculated and the concentration ranges of their existence were determined.