A correction function to determine the β-fusion heat in a mixture of α- and β-PP

Blends of known amounts of α- and β-PP crystals were prepared from pure α- and pure β-PPsamples. Their fusion behaviours were studied by differential scanning calorimetry (DSC).The fusion heats of the α- and β-crystals were approximated from the DSC curves and compared with those calculated on the basis of the compositions of the blends. A correction function was found which improved the accuracy of the respective fusion heats significantly from the DSC analysis. The correction function can be used to determine the respective fusion heats of a PP sample which contains an unknown mixture of the α- and β-crystals. This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetics and thermodynamics of liquid phase isomerization of α- and β-pinene over Pd/C catalyst

The kinetics and thermodynamics of the liquid phase isomerization of an α- and β-pinene mixture on a Pd/C catalyst were studied. The effects of pinene concentration, catalyst particle size, stirring rate, reaction temperature (293–423 K) and hydrogen pressure (0.5–11 bar) on the rate of α- and β-pinene isomerization were investigated. The reaction rate of the α-pinene isomerization has the first order with respect to the α-pinene concentration and 0.5 order with respect to the hydrogen pressure. The thermodynamic parameters of the isomerization (Gibbs energy, reaction enthalpy and reaction entropy) and the equilibrium ratio of pinenes under the conditions studied were determined. The general scheme of the reaction mechanism of α- and β-pinene isomerization over the Pd/C catalyst was proposed.     

The structure and CH-acidity of CF3-substituted β-thiolactones. A theoretical study

Ab initio calculations of the molecules of CH₃- and CF₃-substituted β-propiothiolactones and the productsof their deprotonation were carried out by the restricted Hartree—Fock method with full geometry optimization using the 6–31 G^* basis set. Peculiarities of the geometry and electronic structure of the systems in question were established. Only 2-methyl-β-propiothiolactone forms a mesomeric stabilized carbanion in the case of proton abstraction from the α-position of thiolactone cycle. Carbanions of 3-methyl, 2-, and 3-thrifluoromethyl-β-propiothiolactones are stabilized due to the ring opening to form ketene thiolate ions. The CH-acidity of fluorine-containing β-thiolactones is much higher than that of nonfluorinated analogs (the differences in the deprotonation energies are 13.4 to 25.2 kcal mol⁻¹). Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1719–1725, September, 1998.     

Morpholine Adsorbed on Silica Gel: A Novel and Mild Basic Catalyst for the Synthesis of α,β-Unsaturated Nitroalkenes

Summary.  Syntheses of α,β-unsaturated nitroalkenes have been carried out under mild condition using morpholine adsorbed on silica gel as a novel catalyst. Received February 14, 2000. Accepted March 28, 2000     

Peculiarities of the effects of trifluoromethyl and alkoxycarbonyl groups on the structure and reactivity of acrylates

Ab initio quantum-chemical calculations of molecules of CF₃-substituted acrylates and their non-fluorinated analogs were carried out by the restricted Hartree-Fock (RHF) method and at the second-order Møller-Plesset (MP2) level of perturbation theory using the 6–31G^* basis set with full geometry optimization. Peculiarities of their molecular and electronic structure were revealed and the dipole moments, the polarizability and first molecular hyperpolarizability tensors, harmonic vibrational frequencies, electrostatic potentials, and local electron densities in the vicinity of the carbon atoms of the C=C bond were calculated. It was shown that CF₃-substituted acrylates are conjugated systems similar to their nonfluorinated analogs. Peculiarities of the structure and properties of CF₃-substituted acrylates are explained by p-π-interaction between the CF₃ group and the conjugated system.     

A Novel Preparation of 2-Aminocyclopentanecarboxamides

Summary.  Different syntheses of cis- and trans-2-aminocyclopentanecarboxamides were studied. A convenient and effective method was devised for the preparation of cis-2-aminocyclopentanecarboxamide derivatives starting from the readily available 6-tert-butoxycarbonyl-6-azabicyclo[3.2.0]heptan-7-one. Received November 11, 2001. Accepted (revised) November 26, 2001     

Interaction of polynitro compounds with difluoroamine

Difluoroamine does not react with tetranitromethane and fluoro-, chloro-, and bromotrinitromethanes in DMF and in acidic media (CF₃COOH, ClSO₃H, FSO₃H, and oleum), but reacts with α-fluoro- and α-(difluoroamino)-α,α-dinitrotoluenes to give substitution products of the difluoroamino group for both the nitro groups,viz., PhC(NF₂)₂F and PhC(NF₂)₃, respectively. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1647–1649, August, 1998.     

Electrophilic cyclization of α- and β-geranyl acetates by mercury(II) trifluoroacetate

Electrophilic cyclization of β-geranyl acetate promoted by mercury(II) trifluoroacetate leads to mixtures of α- and γ-5αH-cyclogeranyl acetate derivatives and 6α-hydroxy-5αH-and 6α-hydroxy-5βH-cyclogeranyl acetate derivatives mercurated at the C-3 atom. The ratio of the unsaturated and hydroxymercurated products depends on the reaction conditions. α-Geranyl acetate reacts with mercury(II) trifluoroacetate to give a mixture of 6α-hydroxy-5αH-and 6α-hydroxy-5βH-geranyl acetates, mercurated at C-9, with an equatorial mercurated methylene group at C-4. The mercury-containing groups in mercurated cyclogeranyl derivatives can easily be reduced or replaced by an oxygen-containing functional group; this constitutes a convenient route to polyfunctional cyclogeranyl derivatives that are difficult to obtain. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1320–1324, July, 1997.     

Solid-state interactions and drug release of teicoplanin in binary combinations with peracetylated α-, β-, and γ-cyclodextrins

Triacetyl α-cyclodextrin, triacetyl β-cyclodextrin and triacetyl γ-cyclodextrin were tested as possible hydrophobic carriers to prolong the release of hydrophilic teicoplanin (TCP). Physical–chemical characterization of individual components, drug-carrier physical mixtures at 0.5, 0.67 and 0.75 mass fraction of carrier, and the respective interaction products by kneading or evaporative crystallization under microwave irradiation was carried out using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). In vitro drug release in pH 7.4 phosphate buffer at 37 °C was determined by intrinsic dissolution rate (IDR) measurements on non disintegrating compressed discs. Solid-state interactions of TCP with triacetyl α-cyclodextrin by evaporative crystallization and kneading and with triacetyl β-cyclodextrin by evaporative crystallization (probably resulting in carrier amorphization) were demonstrated. The role of carrier hydrophobicity, carrier mass fraction and preparation method of solid drug-carrier combinations on solid-state drug-carrier interactions and slowing down of TCP release was assessed. Modulation of drug release can be achieved using TCP-triacetyl γ-cyclodextrin combinations at 0.5 mass fraction of carrier.     

Acryloylated α,/β-poly (N-hydroxyethyl)-DL-aspartamide and α,β-polyasparthydrazide. Synthesis, characterization and radiation formation of polymeric networks

 In the present study the derivatization of two water-soluble and synthetic polymers, such as α,β-poly(N-hydroxyethyl)-DL-aspartamide (PHEA) and α,β-polyasparthydrazide (PAHy), with glycidylmethacrylate (GMA) is described. This reaction allowed the introduction of double bonds in the macromolecular chains of PHEA and PAHy in order to make easier the crosslinking by a radical mechanism. Different parameters affected the reaction of derivatization, such as reaction pH, GMA concentration and reaction time. As far as PHEA is concerned the amount of GMA linked to the polymer increased until reaching a plateau. On the contrary, the reaction of PAHy with GMA proceeded with a zero order kinetics and the GMA amount in the polymer increased regularly. Some aqueous solutions of PHEA-GMA and PAHy-GMA copolymers at various GMA content were submitted to gamma radiation processing, thus obtaining crosslinked structures. The derivatization of PHEA and PAHy with GMA was a convenient method to introduce insaturations in their chains and it allowed to obtain gels at lower doses with respect to the starting polymers. Received: 2 April 1996 Accepted: 30 June 1996     

Uncertainty of measurement and legislative limits

 The uncertainty affecting analytical measurements has to be taken into account when evaluating compliance of suspect matrices to legislative limits. To this aim Type 1 and 2 errors must be considered. This necessarily leads to the evaluation of the minimum detectable inadmissible signal, from which the minimum detectable inadmissible concentration can be obtained. The signal of suspect matrices thus has to be compared with the minimum detectable inadmissible signal. This paper aims to discuss practical problems involved in the comparison.     

Synthetic and mechanistic aspects of α-alkylation and α-arylation of β-dicarbonyl compoundsvia their transition metal complexes

Some transition metal complexes of β-dicarbonyl compounds react with electrophiles at α-C. These reactions, carried out under neutral conditions, offer a broader scope than their conventional counterparts, and are generally performed in the presence of stoichiometric or catalytic amounts of strong bases. Mechanistic observations using different reaction conditions are also relevant from a synthetic point of view. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 418–427, March, 1997.     

Efficient and Mild Synthesis of Novel Schiff Bases Via One-Pot,Three-Component Reaction Under Solvent-Free Conditions

A simple, efficient, and cost-effective method has been developed for the synthesis of N,N′-bis(2-hydroxybenzylidene)-1,1-diaminoalkanes through one-pot, three-component reaction of salicylaldehyde, aliphatic aldehydes, and ammonium nitrate in the presence of a base under solvent-free conditions at room temperature.     

Free-radical reactions of methyl trifluoropyruvate with aldehydes

Methyl trifluoropyruvate reacts with aldehydes in the presence of catalytic amounts of benzoyl peroxide at 130–140°C to give β,β,β-trifluoro-α-(methoxycarbonyl)ethyl carboxylates. UV irradiation makes oligomerization of the initial ketoester predominant. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1763–1766, September, 1998.     

Solid state linear-dichroic infrared (IR-LD) spectroscopic characterization of α-and β-glycine polymorphs

IR-LD spectroscopic analysis using nematic liquid crystal suspension as a solid-state orientation technique and the reducing-difference procedure for polarized spectra interpretation are applied to the α-and β-polymorphs of glycine. Both structural analysis and detailed IR band assignments were carried out.     

Zinc-Promoted Reduction of 1,2-Diketones: A Simple, Efficient, and Mild Approach to a-Hydroxy Ketones

Summary.  1,2-Diketones were readily converted to α-hydroxy ketones in high to excellent yields using zinc in saturated ammonium chloride solution. Received June 7, 2001. Accepted (revised) August 7, 2001     

Regioselective phosphorylation of α-N-alkylamino ketones

General preparative methods for regioselective functionalization of α-amino ketones with organophosphorus reagents were developed. Stable phosphorylated derivatives of all their prototropic forms (α-amino ketones, α-hydroxy imines, and β-hydroxy enamines) were obtained for the first time. The relative thermodynamic stability sequence of α-amino ketones was found to be reversed upon their phosphorylation: O-substituted forms were more stable than N-substituted ones, in contrast to the equilibrium between the prototropic isomers. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 288—293, February, 2006.     

On the Reaction between 1-Aza-1,3-dienes and Push-Pull Olefins of the Acyloxymethylidene-malononitrile Type

Summary.  The reaction between push-pull olefins of the acyloxymethylidene-malononitrile type and α, β-unsaturated hydrazones affords selectively 5-alkyl-2-cyano-6-(N′,N′-dimethylhydrazono)-hexa-2,4-dienenitriles. No [4+2]-cycloaddition products were detected. The structure elucidation of the obtained compounds and possible reaction mechanisms are discussed. Received March 9, 2000. Accepted March 20, 2000     

Preparation of 1,3-Dithiol-2-ones from 1,2-Bis-triisopropylsilanylsulfanyl Alkenes Under Mild Acidic Conditions

1,2-Bis-triisopropylsilanylsulfanyl alkenes are readily converted to 1,3-dithiol-2-ones with phosgene under very mild acidic conditions at room temperature.     

Reactions of α-monochloro- and α,α-dichloro-β-oxoaldehyde acetals with bases

α,α-Dichloro-β-oxoaldehyde diethyl acetals decompose under the action of bases (NaOH, MeONa) with cleavage of the carbon-carbon bond and formation of carboxylic acids or their esters and the dichloroacetaldehyde diethyl acetal carbanion. The latter reactsin situ with benzaldehyde to form stable α-chloro-α,β-epoxyacetal. α-Chloro-α-formyl-γ-butyrolactone diethyl acetal is transformed into α-chloro-α-diethoxymethyl-γ-hydroxybutyric acid under the action of an alkali. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 685–687, April, 1998.