The conformations adopted by α,δ-bis(phenoxy)ethane in isotropic and nematic solutions

Abstract

Errors in the calculations of Cheung and Emsley (Liquid Crystals, 13, 265 (1993)) used to derive the populations of α,δ-bis(phenoxy)ethane dissolved in isotropic and nematic liquid crystalline solvents have been corrected, and the results are compared with those obtained on the same molecule by Abe, Iizumi and Kimura (Liquid Crystals, 16, 655 (1994)). The principal difference between these two calculations is that Abe et al., obtain 0·80 as the population of the tg ± t conformers, and they find this to be independent of temperature, whereas the present calculations obtain 0·42 to 0·58 depending upon solvent and temperature.     

An Improved Gas-Liquid Chromatographic Method for the Analysis Of 1,1,1-Trichloro-2,2-BIS(p-Chlorophenyl) Ethane(p,p′-DDT) and Its Metabolites in Milk

Abstract

A rapid method has been developed, in which p,p′-DDT residues are extracted from milk samples with n-hexane, following treatment of the milk with concentrated sulfuric acid. The extract, containing p,p′-DDT residues is then cleaned up on a silica gel column. Electron capture gas chromatography was used to measure the efficiency of the extraction and cleanup procedure. An overall average recovery of 97% was obtained on samples at concentration levels of 0.05 to 1.00 ppm.     

General features of the reaction of 4,4′-difluorobenzophenone with potassium diphenoxide of 2,2-bis (4-hydroxyphenyl)propane

The major factors determining molecular weights of polyarylene-ether ketones formed by the reaction of 4,4-difluorobenzophenone with 2,2-bis(4-hydroxyphenyl)propane in the presence of K₂CO₃ were revealed. The optimum conditions for the preparation of high-molecular-weight polymers were found, and it was demonstrated that it is possible to control their molecular weights ( from 10 000 to 200 000).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2526–2530, October, 1996.     

A notice: incorrect formulation in the synthetic method of 2,2′-bis(diphenylphosphino)biphenyl

The reaction of 2,2′-dilithiobiphenyl with chlorodiphenylphosphine gives a mixture of triphenylphosphine and 5-phenyldibenzophosphole in almost equal quantities. The formation of the latter phosphine was confirmed by X-ray diffraction study of its platinum(II) derivative. The ³¹P and ¹³C NMR data also support the formulation of this reaction. All these experimental facts together clearly demonstrate that the previously reported synthetic method of 2,2′-bis(diphenylphosphino)-biphenyl was erroneously formulated.     

Role of the transition metal complexes of 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (BINAP) in asymmetric catalysis

Metal complexes of 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (BINAP) are being used as a chiral catalysts in many organic reactions. This review highlights recent developments on synthesis of metal BINAPs and its application in various organic synthesis. The studies done on the application of metal BINAPs show a unique reactivity, which enables its use in entirely different sets of chemical transformation.     

The Kinetics of Crystallization of Poly(tetrafluoroethylene) by the Action of γ-Radiation

The kinetics of crystallization of PTFE over the temperature range 287–310 K upon its -irradiation to a dose of 220 kGy was studied using calorimetric procedures. Parameters for the models of radiation-induced growth in the degree of crystallinity (expressed as the mass fraction) of bulk and film polymer specimens were calculated. It was shown that the degree of perfection of crystals produced upon irradiation can be determined from the heat of transition at T 293 K characteristic of PTFE.     

Preparation of a series of NiL(η2-C60) complexes (L = 1,2-bis(diphenylphosphino)ethane,and 1,1′-bis(diphenylphosphino)ferrocene) by zinc dust reduction

A simple method for preparation of nickel-fullerene coordination complexes has been developed. NiLCl₂(Br₂) and C₆₀ mixtures are reduced by zinc dust upon heating in o-dichlorobenzene. Diffusion of hexane into the reaction mixture results in formation of crystals of NiL(η²-C₆₀)?solvent (L = 1,2-bis(diphenylphosphino)ethane (dppe, 1), 1,3-bis(diphenylphosphino)propane (dppp, 2) and 1,1′-bis(diphenylphosphino)ferrocene (dppf, 3)). Nickel coordinates to the 6–6 bonds of C₆₀ by η²- type and has distorted square-planar geometry. The average Ni–C(C₆₀) bond lengths are 1.936(6)–1.977(3)?Å. We found that increase in the P(L)–Ni–P(L) angle and the dihedral angle between the PNiP and CNiC planes results in elongation of the Ni–C(C₆₀) and Ni–P(L) bonds by 0.04–0.06?Å. Complexes 1–3 contain zero-valent nickel since fullerenes are neutral according to the IR- and visible-NIR spectra. Some of the IR-active bands of C₆₀ are split into three bands in spectra of 1–3 due to C₆₀ symmetry lowering, and the F_1u(4) C₆₀ mode is shifted to lower wave numbers due to the π-back donation. The formation of 1–3 is accompanied by appearance of new bands in the visible range at 435–447 and 661–680 nm.     

Noncovalent Functionalization of Multiwalled Carbon Nanotubes by Anionic Polymer Poly(Sodium 4‐Styrenesulfonate) in Water

We have found that polymer poly (sodium 4‐styrenesulfonate) (PSS) is a facile and effective polymer to assist in the dispersion of MWCNTs in aqueous solutions. With the increase of the concentration of PSS solutions, the dispersibility of MWCNTs in PSS solution increases. Cast films of MWCNTs/PSS (2 wt.%) on GC electrode show a typical redox couple at scan rate of 1 V/s in phosphate buffer solution, indicating good electrical conductivity.     

1,4-bis[2,2-bis(trimethylsilyl)ethenyl]benzene: Regioselective ring opening of its α,β-epoxybis(silane) with some nucleophiles

The Peterson olefination reaction of terephthalaldehyde with tris(trimethylsilyl)methyllithium, (Me₃Si)₃CLi, in Et₂O gives disubstituted vinylbis(silane) 1 which reacts with MCPBA in CH₂Cl₂ at r.t. to afford mixture of mono and disubstituted epoxybis(silanes) 3 and 2. Vinylbis(silane) 1 can be completely converted into epoxybis(silane) 2 with an excess amount of MCPBA. The compound 2 was reacted with various reagents such as HX (X = Cl, Br), H₂SO₄, LiAlH₄ and MeLi/CuI and give the related products.     

Mechanism of Dehydrohalogenation of 2,2-Di(4-chlorophenyl)-1,1,1-trichloroethane in NaOH–N,N-Dimethylformamide System: A Quantum-Chemical Approach

Russian Journal of General Chemistry - The processes of alkaline hydrolysis of an amide solvent and the dehydrochlorination reaction of 2,2-di(4-chlorophenyl)-1,1,1-trichloroethane in...     

Proximity effects in the mass spectra of bis(dimethylamino)arenes,III, intramolecular cyclization of 2,2′-bis(dimethylamino)biphenylsunder electron impact

There are not only strongly crowded “proton sponges” that show characteristic [M-Me₂NH-H]⁺ peaks corresponding to cyclization to stable, even electron heterocyclic ions under EI. Fragmentation of title compounds which are moderately strong, not very crowded bases also leads to abundant [M-Me₂NH-H]⁺ phenanthridinium ions, as shown by linked scans, exact mass measurements, MS/MS and collisionally activated dissociation (CAD) mass spectra.     

Optical Rotatory Feature of (R or S)-1,1′-Binaphthalene-2,2′-diol (BINOL) in Various Solvents

IntroductionElieletal.1,2 haveeverreportedthatsolventtypeandconcentrationwouldaffecttheequilibriumofcis 3 hydrox ythiane S oxideconformationwhichwascausedbyintermolec ularandintramolecularhydrogenbondformedwiththeinter actionbetweenthesolute solventandthesolute soluteinthesolutionandhaveimportantinfluenceonitsspecificrotation .Uptonowitisnotveryclear,however,whetherhydrogenbondingaffectsspecificrotation (inmagnitudeandoccasion allyinsign)directlyorwhetheritdoessoindirectly (byaf fectingconform…     

Hydrogen Migration and Reductive Elimination of Alkyne in Fe(CO)4 P(tBu) (C °CPh)H Induced by the Action of Co2 (CO)8

Abstract

One of the possible ways of getting phosphacumulene complexes could be the complexation of phosphinoalkynes, which might induce the migration of hydrogen from phosphorus to the β carbon of the alkynyl group.     

Crystal and molecular structure of N-(4-nitrophenyl)-β-alanine--its vibrational spectra and theoretical calculations

The N-(4-nitrophenyl)-β-alanine in crystalline form directly by the addition of 4-nitroaniline to the acrylic acid in aqueous solution has been obtained. The title β-alanine derivative crystallizes in the P2(1)/c space group of monoclinic system with four molecules per unit cell. The X-ray geometry of β-alanine derivative molecule has been compared with those obtained by molecular orbital calculations corresponding to the gas phase. In the crystal the molecules related by an inversion center interact via symmetrically equivalent O-H···O hydrogen bonds with O···O distance of 2.656(2) ? forming a dimeric structure. The dimers of β-alanine derivative weakly interact via N-H···O hydrogen bonds between the H atom of β-amine groups and one of O atom of nitro groups. The room temperature powder vibrational (infrared and Raman) measurements are in accordance with the X-ray analysis. In aqueous solution of 4-nitroaniline and acrylic acid, the double CC bond of vinyl group of acrylic acid breaks as result of 4-nitroaniline addition.     

Radiolysis of cerium(III) 1,2-bis(β-aminoethoxy)ethane N,N,N′,N′-sodium sulfonate triacetic acid chelate

The publication describes chelation studies of cerium(III) with 1,2-bis(-aminoethoxy)-ethane N,N,N,N-sodium sulfonate triacetic acid (ASTA). The results showed the effectiveness of ASTA as a chelating agent by molar ratio, continuous variation and slope ratio methods. Stable 11 complex was formed at pH from 4 to 8. Aqueous solutions of the chelate of different mole ratios at pH and 7.5 were irradiated by -radiation with different doses. The results show that a decrease of absorbance with increasing absorbed dose was obtained in the dose range studied. A proposed radiolytic mechanism is discussed. The degradation of ligand was due to OH radical.     

Kinetics of the reduction of tetrakis (2,2′-bipyridine)-μ-oxo-di-iron(III) by 1,3-benzenediol in aqueous acidic medium

The stoichiometry and kinetics of the reduction of Fe₂(III)(bpy)₄OCl₄ by 1,3-benzenediol have been investigated in aqueous hydrochloric acid medium. The reaction is first order in [oxidant] but zero order in [reductant]. There is no evidence for the formation of an intermediate complex of significant stability. The presence of NO₃ ⁻ or ClO₄ ⁻ had no effect on the rate of the reaction. Also, the reaction rate is not affected by the changes in the ionic strength and dielectric constant of the reaction media. A plausible mechanism involving an outer-sphere complex formed via an ion pair is proposed for the reaction.     

The decomposition of cumene hydroperoxide by nickel (II) 2,2′-thiobis(4-tert-octyl-phenolato)-n-butylamine (cyasorb UV 1084) in n-hexane solution and its possible importance in the photostabilisation of polypropylene

The thermal decomposition of cumene hydroperoxide (CHP) by the metal complex, 2,2′-thiobis(4-tert-octylphenolato)n-butylamine (Cyasorb UV 1084), in hexane solution and in the temperature range 27–70°, has been examined. The complex is an effective hydroperoxide decomposer at a molar ratio of [CHP]/[complex] = 0.19; at higher molar ratios, an induction period is present. The peroxidolytic effect increases with temperature rise and is attributed to a homolytic mechanism at low ratios of hydroperoxide to complex and to an ionic mechanism when the former is in excess. Kinetic analysis of the data yielded rate constants of 1.06 × 10⁻⁵sec⁻¹ at 27° and 2.38 × 10⁻³sec⁻¹ at 200°, at low ratios of CHP to complex, highlighting the efficiency of the process at high temperatures. The latter, coupled with the observed antioxidant behaviour of this metal complex in polypropylene during both processing and photooxidative conditions, lead to the conclusion that hydroperoxide decomposition must play an important role in the stabilising action of Cyasorb UV 1084 in this polymer.     

S- and N-alkylation of 2,2′-(alkane-α,ω-diyldisulfanediyl)-bis(1,3-benzothiazoles) with 1-iodopropan-2-one in the presence of iodine

Russian Journal of Organic Chemistry - The alkylation of 2,2′-(methylenedisulfanediyl)- and 2,2′-(ethane-1,2-diyldisulfanediyl)bis-(1,3-benzothiazoles) with 1-iodopropan-2-one involves...