Copper-catalyzed allylations of zirconocene intermediates generated from o-alkenyl or o-alkynylbenzyl ether derivatives and zirconocene-butene complex

o-Alkenyl or alkynyl benzylzirconocene intermediate, which was readily generated by the reaction of 2-alkoxymethylstyrene or 2-alkoxymethyl-1-(trimethylsilylethynyl)-benzene derivative with zirconocene-butene complex (Negishi reagent, "Cp2Zr"), reacted with allyl or propargyl halides in the presence of a catalytic amount of CuCl to give allylation or allenylation products. Conversion to Dane's diene, which is a key intermediate for estrone synthesis, was efficiently carried out by enyne olefin metathesis of the allylation products.     

Spectrophotometric determination of manganese with 1-(2-pyridylazo)-2-naphthol and a non-ionic surfactant

A spectrophotometric method for the determination of trace amounts of manganese with 1-(2-pyridylazo)-2-naphthol (PAN) is described. The method is based on the measurement of absorbance of the manganese—PAN chelate solubilized with a non-ionic surfactant, Triton X-100. No extraction procedure is required in the method proposed. High concentrations of calcium, aluminium and magnesium do not interfere. The presence of up to 10 ppm of lead can be tolerated. Iron, cadmium, zinc, cobalt and nickel can be effectively masked with potassium cyanide. Beer's law is obeyed up to 2 ppm of manganese. The molar absorptivity of the manganese—PAN chelate found was 4.4 × 10⁴ l. mole ⁻¹. cm⁻¹ at 562 nm. The overall stability constant of Mn(PAN)₂ in 0.4% Triton X-100 medium is 10^16.8.     

Stability Constants for 1:1 Complexes Formed between2-hydroxypropyl-β-Cyclodextrin with an Average Substitution Degree of 4.4 and Benzene and Alkylbenzenes as Guests by Modified Static Head-Space Gas Chromatography Method

Modified static head-space gas chromatography method (M-SHSGC method) was used to determine the stability constants of benzene and alkylbenzenes with 2-hydroxypropyl-β-cyclodextrin inclusion complexes. The 1:1 stability constants were in agreement with those obtained by conventional SHSGC method. The M-SHSGC method precludes the necessity of the calibration curve by the use of Henry’s law constant of guest. Consequently, it is more advantageous than conventional SHSGC method because the time required to determine the stability constant is markedly reduced.     

Rotational diffusion of tungstic acid colloids in microgravity as studied by aircraft experiments

 Rotational relaxation times (τ) of anisotropic tungstic acid colloids (3.24 μm in major axis) in aqueous suspension are measured in microgravity (0G), normal gravity (1G) and at 2G. The measurements at 0G and 2G are achieved by parabolic and circular flights, respectively. The limiting slopes of the relaxation curves in the plots of the transmitted light intensity against time are close to zero at 0G irrespective of the flow directions in the flow cell, whereas those at 1G and especially at 2G depend on the flow direction by the convection of the suspension and particle sedimentation. Experimental errors at the τ values at 0G are small compared with those at 1G and 2G, which is ascribed to the lack of movement of impurities in the suspension such as quite small air bubbles, which cannot be recognized with the naked eye, and the convection of the suspension in microgravity. More reliable rotational relaxation times are obtained in microgravity; however, the relaxation times themselves are quite insensitive to gravity. Theτ values observed are larger than those calculated from the particle size, which indicates the important contribution of the electrical double layers formed around the colloidal particles. Received: 22 February 2001 Accepted: 13 June 2001     

Bis[2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulpho propylamino)phenolato]cobaltate(III) as a counter ion for the extraction and spectrophotometric determination of long-chain quaternary ammonium salts and tertiary alkylamines in the presence of each other

The singly charged complex anion bis[2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulphopropylamino)phenolato]cobaltate(III) is intensely purple-violet and is stable over the pH range 1–13. Its absorption spectrum remains the same over this pH range. At pH2, it forms extractable ion pairs with long-chain quaternary ammonium ions and protonated alkylamines. Only the quaternary ammonium ions are extracted into chloroform at pH 11, hence separate extractions allow both types to be determined. The absorbance of the organic phase is measured at 594 nm. The apparent molar absorptivity is 7.0 × 10⁴ l mol^?1 cm^?1. Calibration graphs for zephiramine, benzethonium and hexadecylpyridinium ions are linear over the range 0.1–2 × 10^?6 M. The only interference found was from anionic surfactants. The method is applied to hair and fabric conditioners.     

Orientational order in binary mixtures of hard Gaussian overlap molecules

Based on a standard constant-pressure Monte Carlo molecular simulation, we have studied liquid crystal phases of binary mixtures of nonspherical molecules. The components of the mixtures are two types of hard Gaussian overlap (HGO) molecules. The first type of molecule has a small molecularelongation parameter (short HGO molecules) and cannot form stable liquid crystal phase in the bulk by themselves. The second type of molecule has a large elongation parameter (long HGO molecules) and can form a liquid crystal phase easily. In the mixtures, the short HGO molecules can form an orientationally ordered phase because the long HGO molecules form confining surfaces to induce the alignment of the short molecules. We also study the isotropic-nematic phase transition in different mixtures composed of short and long HGO molecules with different elongations and concentrations. The obtained result implies that small anisotropic molecules can show liquid crystal behavior.     

Membrane filters for the concentration of trace elements in water: distribution of ion pairs between membrane filter and aqueous phases

The sorption of ion pairs on membrane filters (MFs) has been studied by taking the membrane filter as one of the homogeneous phases. The sorbability of some ionic species and the sorption abilities of different types of MF were evaluated in terms of the sorption constant defined by Ksor,CA = [(C+,A-)f]/[C+][A-], where C+, A- and (C+,A-) refer to the cation, anion and the ion pair, respectively, and f refers to the filter phase. The values of Ksor,CA were determined for many combinations of ionic complexes of cobalt(III) with pyridylazophenols, either as cations or anions, and oppositely charged organic ions having different alkyl chain lengths, with MFs made of different materials: nitrocellulose (NC; Toyo Advantec), acetylcellulose (AC; Fuji Film), regenerated cellulose (RC; Toyo Advantec) and polyethersulphone (PS; Toyo Advantec). For a given cobalt complex ion, the value of log Ksor,CA increased linearly with the increasing number of carbons in the counter ion. Membrane filters made of different materials showed different sorption abilities, the order being NC greater than PS greater than RC greater than AC. It was shown that the surface area of the MF is of greater significance than the volume of the matrix of the MF in determining the sorption constant.