A DFT study of the mechanism and the regioselectivity of [3 + 2] cycloaddition reactions of nitrile oxides with α,β-acetylenic aldehyde

A DFT study of the (32CA) reaction of a series of some nitrile oxides with electron-deficient alkyne (3-phenylpropionlaldehyde) in gas phase and in toluene has been carried out using B3LYP functional with 6-31G(d) basis set. Two reactive channels 4- and 5-associated with the two regioisomeric modes have been located and characterised. These 32CA reactions are characterised by a low asynchronous one-step mechanism with a low-polar character. Analysis of the DFT reactivity indices indicates that the nucleophilic centre of the different nitrile oxides accounts for the 4-regioselectivity. Our calculations are in a good agreement with the experimental findings.     

A theoretical investigation of the regio- and stereoselectivities of the 1,3-dipolar cycloaddition of C-diethoxyphosphoryl-N-methylnitrone with substituted alkenes

A theoretical study of the regio- and stereoselectivities of the 1,3-dipolar cycloaddition of C-diethoxyphosphoryl-N-methylnitrone with substituted alkenes (allyl alcohol and methyl acrylate) is carried out using DFT at the B3LYP/6-31G(d,p) level of theory. The FMO analysis and DFT-based reactivity indices confirmed the experimental ortho regioisomeric pathway. Potential energy surface analysis shows that these 1,3-dipolar cycloaddition reactions favor the formation of the ortho-trans cycloadduct in both cases. The obtained results are in agreement with experimental data.     

Effectively Rifampicin loaded microspheres based on blends of high- and low-molecular-mass polylactic acid

Specific features of immobilization of Rifampicin drug by poly-D,L-lactic acid microparticles and the possibility of controlling the uniform Rifampicin release were studied.     

4-cycle properties for characterizing rectagraphs and hypercubes

A (0, 2)-graph is a connected graph, where each pair of vertices has either 0 or 2 common neighbours. These graphs constitute a subclass of (0, λ)-graphs introduced by Mulder in 1979. A rectagraph, well known in diagram geometry, is a triangle-free (0, 2)-graph. (0, 2)-graphs include hypercubes, folded cube graphs and some particular graphs such as icosahedral graph, Shrikhande graph, Klein graph, Gewirtz graph, etc. In this paper, we give some local properties of 4-cycles in (0, λ)-graphs and more specifically in (0, 2)-graphs, leading to new characterizations of rectagraphs and hypercubes.     

Nonlinear optical responses of Sudan IV doped liquid crystal by z-scan and moiré deflectometry techniques

The nonlinear optical properties of a nematic liquid crystal doped with an azo dye were investigated. The magnitude and the sign of the third-order nonlinear refractive index, n₂, were measured using both single-beam z-scan and moiré deflectometry techniques. The measurements were performed at 532 nm using a Nd:Yag CW laser. The positive sign showed that sample which was studied possess a self-focusing optical nonlinearity. Rather close agreement was found between the values for n₂ obtained by z-scan and by moiré deflectometry. The nonlinear refractive index was found to be in the order of 10^− 6 (cm²/W) and the nonlinear absorption coefficient to be β = 0.171 (cm/W).     

Soluble minimal non-(finite-by-Baer)-groups

Let \mathfrakX{\mathfrak{X}} be a class of groups. A group G is called a minimal non- \mathfrakX{\mathfrak{X}}-group if it is not an \mathfrakX{\mathfrak{X}}-group but all of whose proper subgroups are \mathfrakX{\mathfrak{X}}-groups. In [16], Xu proved that if G is a soluble minimal non-Baer-group, then G/G ^′′ is a minimal non-nilpotent-group which possesses a maximal subgroup. In the present note, we prove that if G is a soluble minimal non-(finite-by-Baer)-group, then for all integer n ≥ 2, G/γ _n (G′) is a minimal non-(finite-by-abelian)-group.     

Nonlinear responses and optical limiting behavior of fast green FCF dye under a low power CW He-Ne laser irradiation

The nonlinear responses and optical limiting performance of a dye type acid, called fast green FCF, are investigated under irradiation of 35 mW continuous wave He-Ne Laser. The second order refractive index and nonlinear absorption coefficient are measured by use of z-Scan technique. The optical limiting behavior is investigated by transmission measurement through the sample. Linear absorption coefficient (α), nonlinear absorption coefficient (β) and second order refractive index (n₂) of fast green FCF are measured at different concentrations.     

Synthese de 2h-pyrroles et de pyrroles: action de carbanions sur des 2H-azirines ou des sels de N,N,N-trimethylhydrazonium

Dimsyl sodium reacts with 2H-azirines 2 to give amino ethylenic sulfoxide 5E. The same reaction is observed from N,N,N-trimethylhydrazonium salt 1 using an excess of dimsylsodium. Carbanions of ketone or nitrile react with 2H-azirine or N,N,N-trimethylhydrazonium to produce 2H-pyrroles 6–13, 20 or pyrroles 18, 19. This reaction is the most convenient general route to 2H-pyrroles.     

Effect of preparation conditions on properties of polylactide and polystyrene and their composite microparticles made by emulsion solvent evaporation method

In this study, polylactide and polystyrene microparticles have been prepared by emulsion solvent evaporation method. Effects of polymer nature, stirring speed, emulsifier, and concentration of the components on the size, size distribution and morphology of polymeric microparticles have been investigated. 11-Acryloyl-aminoundecanoic acid and its polymer poly(11-acryloyl-aminoundecanoic acid) were tested for comparison with traditional emulsifiers such as sodium dodecylsulfate. Interfacial tension measurement was applied to compare these emulsifiers. Dynamic light scattering and scanning electron microscopy were used to analyze microparticles. Polylactide/polystyrene composite microparticles have been prepared as well; their surface morphology has been studied.