The cleaning of ultrafiltration membranes fouled by protein

The relationship between membrane fouling and cleaning was investigated in terms of flow conditions, transmembrane pressures, pH, membrane properties, and cleaning agents using a stirred batch cell and aqueous albumin solution. Fouling was less at the pH extremes than at the isoelectric point for both retentive and partially permeable membranes. Membranes with partial permeability showed a greater tendency for fouling and were less responsive to cleaning than retentive membranes. The results in the stirred cell were shown to be similar to those for a crossflow module under similar operating conditions.     

The crystal and molecular structure of 7-con-O-methylnogarol

A crystal structure analysis for 7-con-O-methylnogarol free base, a promising antitumor antibiotic of the nogalamycin family, has been carried out with low temperature X-ray diffraction data. The relative configuration of the anthracycline moiety is C7(S) and C9(S); the sugar moiety is an α-D-3,6-dideoxy-3-dimethylaminoglucose.     

Bulky aluminum alkyl scavengers in olefin polymerization with group 4 catalysts

The binding of H2O to MeAl(OAr)2 (1: Ar = 2,6-di-tert-butyl-4-methylphenyl) in THF-d8 at -40 degrees C provides aquo complex 2, the structure of which was determined by X-ray crystallography. Complex 2 is unstable above 0 degrees C in THF-d8 and decomposes to form ArOH (major), CH4 (minor), and a methyl aluminoxane of undetermined structure. Decomposition of 2 follows first-order kinetics with k = 3.0 x 10-4 s-1 at 5 degrees C. The hindered phenol ArOH slowly reacts with [Cp2ZrMe][MeB(C6F5)3] (4) in bromobenzene-d5 solution at 25 degrees C to furnish CH4 and [Cp2ZrOAr][MeB(C6F5)3] (5), the structure of which was confirmed by X-ray crystallography. This reaction follows second-order kinetics for [ArOH] = [4] = 0.045 M and with k = 2.8 x 10-3 M-1 s-1 at 25 degrees C. This corresponds to a rate that is >107 x slower than the apparent rate of ethylene insertion for 4 at 25 degrees C at typical concentrations encountered in olefin polymerization. The kinetic data, as well as control experiments involving the addition of ArOH to active catalyst producing poly(ethylene), demonstrate that ArOH has essentially no effect on polymerization kinetics involving 4.     

Application of aryloximes as solid-phase ketone linkers

In both solution and the solid phase, a variety of ketone oxime anions have been treated with 4-substituted-2-fluorobenzonitriles to give the corresponding nucleophilic aromatic substitution aryloxime adducts. Under aqueous acidic conditions, these adducts underwent cyclization to give the corresponding ketones. Suzuki and amide coupling reactions were also successfully performed on two resin-bound oximes followed by subsequent cyclorelease to give ketone product in good yields and purities. [reaction--see text]     

Lewis acid adducts of [PCl2N]3

Reaction of aluminum trichloride or gallium trichloride with the extremely weak base hexachlorotriphosphazene gives adducts in which the group 13 element is bound to a phosphazene nitrogen atom. In solution, the adducts exhibit fluxional behavior. The phosphazene ring of the adducts is distorted into a slight chair conformation.     

Monomer reactivity ratios for the copolymerization of styrene with 1,2,4-trivinyl and p-divinylbenzenes

The copolymerization kinetics of 1,2,4-trivinylbenzene (TVB) with styrene do not clearly resemble those of o-, m-, or p-divinylbenzene (DVB), structural elements of which are present in TVB. A control determination of the reactivity ratios for the styrene-p-DVB pair under different conditions (70°C., pre-gel point conversion), run for comparison with the TVB data, show values (r₁ = 0.77; r₂ = 1.46) similar to those previously recorded (r₁ = 0.77; r₂ = 2.08).