A CONVENIENT ONE-POT METHOD OF CONVERTING ALCOHOLS INTO OXIMES

The one-pot conversion of[3pc] primary and secondary alcohols into oximes is reported using chromium trioxide supported on alumina and hydroxylamine hydrochloride under solvent free condition. This oxidation-oxime formation reaction has been applied to a range of aliphatic and benzylic alcohols.     

First principle study of the electronic and magnetic properties of a single iron atomic chain encapsulated in boron nitrite nanotubes

The electronic and magnetic properties for a single Fe atom chain wrapped in armchair (n,n) boron nitride nanotubes (BNNTs) (4≤n≤6) are investigated through the density functional theory. By increasing the nanotube diameter, the magnetic moments, total magnetic moments and spin polarization of systems are increased. We have calculated the majority and minority density of states (DOS) of armchair BNNT. Our results show that the magnetic moment of the system come mostly from the Fe atom chain. The magnetic moment on an Fe atom, the total magnetic moment and spin polarization decrease by increasing the axial separation of the Fe atom chain for the system. The BNNT can be used in the magnetic nanodevices because of higher magnetic moment and spin polarization.     

Darkening enhancement in SK3 glass with quartz under irradiation of femtosecond laser pulses

In this paper, the femtosecond laser-induced darkening in SK3 glass is investigated. A sample with 3-mm thickness is irradiated with 200 fs laser pulses (FLP) at 800 nm wavelength and 1 kHz repetition rate. When a piece of quartz or sapphire, which does not show darkening effect under IR irradiations, is placed in front of the sample, the laser-induced darkening is enhanced. The directly darkened region in the sample gets darker on placing a piece of quartz or sapphire in front of the sample. When a piece of ULE glass that shows darkening effect by IR-FLP irradiations is placed in front of the sample, SK3 sample does not get that dark. We believe the enhancement of the darkening in SK3 glass sample by the quartz or sapphire is related to the absorption of the short wavelength component of the white light, which is generated and not absorbed in the quartz or sapphire.     

A redox series of aluminum complexes: characterization of four oxidation states including a ligand biradical state stabilized via exchange coupling

Electrophilic activation and subsequent reduction of substrates is in general not possible because highly Lewis acidic metals lack access to multiple redox states. Herein, we demonstrate that transition metal-like redox processes and electronic structure and magnetic properties can be imparted to aluminum(III). Bis(iminopyridine) complexes containing neutral, monoanionic, and dianionic iminopyridine ligands (IP) have been characterized structurally and electronically; yellow (IP)AlCl(3) (1), deep green (IP(-))(2)AlCl (2) and (IP(-))(2)Al(CF(3)SO(3)) (3), and deep purple [(IP(2-))Al](-) (5) are presented. The mixed-valent, monoradical complex (IP(-))(IP(2-))Al is unstable toward C-C coupling, and [(IP(2-))Al](2-)(μ-IP-IP)(2-) (4) has been isolated. Variable-temperature magnetic susceptibility and EPR spectroscopy measurements indicate that the biradical character of the ligand-based triplet in 2 is stabilized by strong antiferromagnetic exchange coupling mediated by aluminum(III): J = -230 cm(-1) for ? = -2J(?(L(1))·?(L(2))). Coordination geometry-dependent (IP(-))-(IP(-)) communication through aluminum(III) is observed electrochemically. The cyclic voltammogram of trigonal bipyramidal 2 displays successive ligand-based oxidation events for the two IP(1-/0) processes, at -0.86 and -1.20 V vs SCE. The 0.34 V spacing between redox couples corresponds to a conproportionation constant of K(c) = 10(5.8) for the process (IP(-))(2)AlCl + (IP)(2)AlCl → 2(IP(-))(IP)AlCl consistent with Robin and Day Class II mixed-valent behavior. Tetrahedral 5 displays localized, Class I behavior as indicated by closely spaced redox couples. Furthermore, CV's of 2 and 5 indicate that changes in the coordination environment of the aluminum center shift the potentials for the IP(1-/0) and IP(2-/1-) redox couples by up to 0.9 V.     

Novel method for ultraviolet protection and flame retardancy of cotton fabrics by low-temperature plasma

A novel approach, namely the nitrogen plasma technique, to confer flame-retardant and ultraviolet (UV)-protective properties on cotton fabric is described. Treated cotton fabrics showed very good UV-blocking property. According to the standard, the treated cotton fabric can be claimed to be a “UV-protective” product. The fire-retardant character of the treated fabrics was investigated by char yield, thermogravimetric analysis, and limiting oxygen index measurements. Also, the effect of aging on the mentioned properties was studied. The ultraviolet protection factor and flame-retardant properties of atmospheric pressure plasma-treated cotton were also measured and compared with nitrogen plasma treatment.     

Safe and Efficient Reductive Methylation of Primary and Secondary Amines Using N-Methylpyrrolidine Zinc Borohydride

An efficient, general procedure for reductive methylation of primary and secondary amines with 37% formaldehyde using N-methylpyrrolidine zinc borohydride (ZBHNMP) as a reducing agent gave the corresponding tertiary amines in excellent yields. The reaction was carried out in tetrahydrofuran under neutral conditions at 0–10 °C.     

Thermodynamic study for dicyclohexano-24-crown-8 complexes with K+, Rb+, Cs+ and Tl+ ions in binary acetonitrile–nitromethane mixtures by conductometric method

The complexation reactions between dicyclohexano-24-crown-8 (DC24C8) and K⁺, Rb⁺, Cs⁺ and Tl⁺ ions were studied conductometrically in the different acetonitrile-nitromethane mixtures at various temperatures. The formation constants of the resulting 1:1 complexes were calculated from the computer fitting of the molar conductance-mole ratio data at different temperatures. At 25 °C and in all solvent mixtures used, the stability of the resulting complexes varied in order of Tl⁺ > K⁺ > Rb⁺ ~ Cs⁺. The enthalpy and entropy changes of the complexation reactions were evaluated by the temperature dependence of formation constants. It was found that the stability of the resulting complexes increased with increasing nitromethane in the solvent mixture.     

Synthesis of 1,1-bis(silyl)-1-alkene derivatives bearing Si-H functional groups via Peterson protocol

Various aromatic aldehydes were converted to one-carbon elongate 1,1-bis(silyl)-1-alkene derivatives bearing Si-H functional and reactive groups in a convenient one-pot operation via the Peterson protocol. Then poly(styrene) and poly(α-methylstyrene) (?&II) random homopolymers were synthesized by solution free radical polymerization at 70(±1) °C using α,α′-azobis(isobutyronitrile) (AIBN) as an initiator. The aldehyde group is introduced by direct electrophilic substitution of polymers ? and II. This formylation reaction was conducted in two different solvents: dichloromethane (CH₂Cl₂) and nitrobenzene (PhNO₂). The results indicate that PhNO₂ appeared to be a more suitable solvent for such an aldehyde functionalization of the polymers. The formylated polymers (I_CHO, II_CHO) were then converted to Si-H functionalized polymers (I_Si-H, II_Si-H) via reaction with tris(dimethylsilyl)methyllithium, (HMe₂Si)₃CLi.     

Synthesis of Novel Indolo‐Spirocyclic Compounds

In the present work, we succeeded to synthesize the novel indolo‐spirocyclic compounds ( 4 , 5 , 6 , 7 and 11 ) via electrophilic condensation reactions of indoles with carbonyl compounds including different types of ketones, for example, heteroacetyl ketones (3‐acetylindole and 3‐acetylpyridine), cyclohexanone, isatin, cyclohexane‐1,4‐dione, whereas an attempt to prepare the spirocyclic 9 failed. This new idea will open a high prospective for continuous investigations related to the synthesis of novel indolo‐spirocyclic compounds.