Ozonolysis of alkenes and study of reactions of polyfunctional compounds: LXVIII. Investigation of transformations of peroxide products of olefins ozonolysis treated with hydroxylamine hydrochloride

Hydroxylamine hydrochloride efficiently reduces peroxide products of olefins ozonolysis into carbonyl compounds. Depending on the substrate character, solvent, and the treatment conditions the arising aldehydes transformed along the route aldehyde→aldoxime→nitrile→ester into individual compounds or their mixtures, or give the corresponding acetals.     

Synthesis,structure, and biologic activity of products of reactions between dinitrodichlorobenzofuroxane and aminopyrimidines in aqueous dimethyl sulfoxide

Reactions of 4,6-dinitro-5,7-dichlorobenzofuroxane with substituted pyrimidines in aqueous DMSO proceed through an intermediate formation of 5-hydroxy-4,6-dinitro-7-chlorobenzofuroxane owing to the hydrolysis of one of the chlorine atoms with the subsequent formation of pyrimidine salts exhibiting a high biologic action.     

Kinetics and mechanism of the Pudovik reaction in the azomethine series: III. Acid-catalyzed hydrophosphorylation of imines

A complex spectral (UV, IR, and ³¹P NMR), preparative, and kinetic investigation of the mechanism of the noncatalytic variant of the Pudovik reaction in the series of imines was carried out. The reaction proceeds through a four-center cyclic transition state. The transition state is highly labile, which determines its high sensitivity to the structure of the reagents, the nature of the solvent and catalyst, and some other factors. The necessary condition for the hydrophosphorylation of imines to occur is the participation of proton-donor reagents and acidic admixtures, specifically hydrolysis products of dialkyl hydrogen phosphites, such as monoalkyl dihydrogen phosphates and phosphorous acid, which act as acid catalysts. When the starting reagents are thoroughly purified and no such catalysts are present, the Pudovik reaction fails to occur in the imine series.     

Spinodal for the solution-to-crystal phase transformation

The formation of crystalline nuclei from solution has been shown for many systems to occur in two steps: the formation of quasidroplets of a disordered intermediate, followed by the nucleation of ordered crystalline embryos within these droplets. The rate of each step depends on a respective free-energy barrier and on the growth rate of its near-critical clusters. We address experimentally the relative significance of the free-energy barriers and the kinetic factors for the nucleation of crystals from solution using a model protein system. We show that crystal nucleation is 8-10 orders of magnitude slower than the nucleation of dense liquid droplets, i.e., the second step is rate determining. We show that at supersaturations of three or four k(B)T units, crystal nuclei of five, four, or three molecules transform into single-molecule nuclei, i.e., the significant nucleation barrier vanishes below the thermal energy of the molecules. We show that the main factor, which determines the rate of crystal nucleation, is the slow growth of the near-critical ordered clusters within the quasidroplets of the disordered intermediate. Analogous to the spinodal in supersaturated fluids, we define a solution-to-crystal spinodal from the transition to single-molecule crystalline nuclei. We show that heterogeneous nucleation centers accelerate nucleation not only because of the wettinglike effects that lower the nucleation barrier, as envisioned by classical theory, but by helping the kinetics of growth of the ordered crystalline embryos.     

The kinetic regularities, products, and mechanism of the thermal decomposition of dimethyldioxirane. The contribution of molecular and radical reaction channels

The products and kinetics of the thermal decomposition of dimethyldioxirane (DMDO) were studied. The reaction proceedsvia three parallel pathways: isomerization to methyl acetate, oxygen atom insertion into the C−H bond of a solvent molecule (acetone), and the solvent-induced homolysis of the O−O bond in the DMDO molecule. The contribution of the latter reaction channel isca. 23% at 56°C. The overall kinetic parameters of DMDO thermolysis in oxygen atmosphere were determined. The free radical-induced DMDO decomposition occurs in an inert atmosphere. The formal kinetics of this reaction was investigated. The mechanism of the DMDO thermolysis is discussed. Dedicated to Professor E. T. Denisov on the occasion of his 70th Birthday. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1344–1354, August, 2000.     

New phosphonium salts based on 3-(diphenylphosphino)propanoic and ω-haloalkanoic acids

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N-Substituted tetrahydro-1,3-oxazines and oxazolidines. 1. A new version of the Mannich reaction involving amino alcohols

A new version of the Mannich reaction involving amino alcohols (3-aminopropan-1-ol and aminoethanol) was developed. These compounds react with formaldehyde and CH or NH acids to give N-substituted tetrahydro-1,3-oxazines or oxazolidines.     

Asymptotic theory of the asymmetry parameters of a weak shock wave

A theory of the asymmetry parameters of a weak shock wave in a binary gas mixture, based on the expansion of the solutions of the Burnett equations in series in a small parameter of the shock wave intensity, that ensures the asymptotic accuracy of the required data, is given. The dependence of the solution on the characteristics of the mixture is examined. The known results for a polyatomic gas are refined and supplemented.