N-Hydroxy-N-m-tolyl-N′-(2-methyl-5-chloro)phenyl-p-toluamidine hydrochloride (HTMCPTH), a monobasic and bidentate chelating agent which reacts with vanadium(V) in carboxylic acid media to develop a blue-violet complex, has been employed as a highly selective reagent for extraction and direct photometric determination of the metal. Solvent extraction experiments indicate that from aqueous acetic acid (1.0–10.0 M), monochloroacetic acid (0.1–10.0 M), and phenylacetic acid (at pH 0.5–6.0) vanadium(V) is quantitatively extracted into chloroform. Almost all common ions including Fe3+, Cu2+, Ni2+, Co2+, Mn2+, Cr3+, Ti4+, Zr4+, and Mo6+ do not interfere with the proposed method. The procedure has been utilized for accurate determination of vanadium in standard steels. 相似文献
Solutions of CoII salts of organic acids in primary amines absorb molecular oxygen rapidly and irreversibly forming μ-dioxygen—cobalt complexes. Thermolysis leads to a homopolar cleavage of the OO bond with subsequent radical reactions involving ligand amine. After thermolysis the capacity of oxygen uptake is reestablished (catalysis). 相似文献
A first theoretical study of surfactant-stabilized carbon nanotube dispersions is presented. Density functional theory is used to compute potential of mean force between nanotubes in an aqueous solution of cationic surfactant n-decyltrimethylammonium chloride. In agreement with experimental results, it is found that stable dispersions can be prepared for surfactant bulk concentrations below the critical micelle concentration. Computed density profiles of head and tail segments indicate that surfactants adsorb on nanotube surfaces in a random fashion rather than form cylindrical micelles, which is also in agreement with recent small-angle neutron scattering measurements. 相似文献
Production of the end products of polygalacturonic acid degradation on a large scale was done by reacting free galacturonic acid with Bacillus pumilus polygalacturonic acid transeliminase (PATE, EC 4.2.2.2) to obtain a mixture of the barium salts of several oligouronides. Small amounts of the unsaturated oligouronides were separated by paper chromatography. Large quantities of unsaturated oligouronides were separated on a AG-1-X8 (formate) column by applying a sample of mixed oligouronides and stepwise elution was carried out with sodium formate buffer (pH 4.7). The unsaturated oligouronides were identified on the basis of chromatographic mobilities, Sephadex gel filtration data, COOH/CHO ratio, thiobarbituric acid-reacting material, bromine uptake, and chemical and enzymatic degradation data as unsaturated tri-, tetra-, and hexagalacturonic acids. The chemical degradation of these unsaturated oligouronides, done with 6 N HCl by heating at 100 degrees for 30 min, gave qualitatively identical products of hydrolysis. These products compared with authentic standards, were identified as galacturonic acid, formic acid, 5-formyl-2-furancarboxylic acid, and 2-furancarboxylic acid. Analysis of the enzymatic breakdown products of the higher unsaturated uronides showed that a minimum of four galacturonic acid units was required for the action of purified endo-PATE from B. pumilus. The unsaturated trimer was not attacked, thus accounting for its accumulation as the major end product of polygalacturonate degradation by this enzyme. 相似文献
Thioacetals and thioketals of various aldehydes and ketones were obtained directly from carbonyl compounds or by a transthioacetalisation process from cyclic O,O-acetals in the presence of dithiols and a catalytic amount of tetrabutylammonium tribromide (TBATB). Chemoselective thioacetalisation of aromatic aldehydes containing an electron-donating group in the presence of an aldehyde containing an electron-withdrawing group, aldehydes in the presence of ketones, aliphatic cyclic ketones in the presence of aromatic ketones and less hindered ketones in the presence of more hindered ketones have been achieved. A cyclic acetal containing an electron-donating group has been chemoselectively transthioacetalised in the presence of an acetal having an electron-withdrawing substituent. These selectivities are due to the intrinsic reactivity of the substrate themselves and are independent of the catalyst and reaction conditions. Shorter reaction times, mild reaction conditions, stability of acid sensitive protecting groups, high efficiencies, facile isolation of the desired products and the catalytic nature of the reagent are the attractive features of the present method. 相似文献
A spectrophotometric method for determination of a microgram quantity of cerium with N-p-tolyl-p-chlorobenzohydroxamic acid is described. The orange-red-colored complex is extracted from chloroform at pH 9 which absorbs between 460 and 465 nm. Beer's law is obeyed at this wavelength. A clean-cut separation from many commonly occurring metal ions is easily accomplished. The system obeys Beer's law within the range of 0.5–28 ppm of cerium(IV). The molar absorptivity of cerium-N-p-tolyl-p-chlorobenzohydroxamic acid complex is 4.5 × 103 liters mol?1 cm?1. 相似文献
Life-threatening diseases, especially those caused by pathogens and harmful ultraviolet radiation (UV-R), have triggered increasing demands for comfortable, antimicrobial, and UV-R protective clothing with a long service life. However, developing such textiles with exceptional wash durability is still challenging. Herein, we demonstrate how to fabricate wash durable multifunctional cotton textiles by growing in situ ZnO-TiO2 hybrid nanocrystals (NCs) on the surface of cellulosic fabrics. The ZnO-TiO2 hybrid NCs presented high functional efficiency, owing to their high charge transfer/separation. Ultrafine fiber surface pores, utilized as nucleating sites, endowed the uniform growth of NCs and their physical locking. The resulting fabrics presented excellent UV protection factors up to 54, displayed bactericidal efficiency of 100% against Staphylococcus aureus and Escherichia coli, and optimum self-cleaning efficacy. Moreover, the functionalized textiles exhibited robust washing durability, maintaining antibacterial and anti-UV-R efficiency even after 30 extensive washing cycles.
The kinetics of vesicle formation from a hydrotrope (sodium xylenesulfonate) solution of a surfactant (Laureth 4) is studied
by the use of a stopped-flow apparatus combined with a dynamic light scattering device to determine vesicle size in the system.
The hydrotrope system studied presents a system with a high surfactant solubilization combined with vesicle formation simply
by dilution with water. The kinetic results show a single exponential decay time. The kinetic analysis indicates that the
vesicles are formed from a molecular solution which resulted from the shear in the stopped-flow device and grow by monomeric
association.
Received: 1 October 1996 Accepted: 22 November 1996 相似文献
Abstract— Hydroxyl radicals ('OH) are scavenged by 1,4-diazabicyclo[2.2.2]octane (DABCO) at a diffusion-controlled rate of 1.25 ± 0.1 × 109 M -1s-1. Unlike other efficient 'OH scavengers which exhibit protection of bacteria against irradiation both in oxic and hypoxic conditions, DABCO has been shown to protect Serratia marcescens and various strains of Escherichia coli only in oxic conditions. DABCO appears to eliminate a component of the sensitization afforded by oxygen in all strains of E. coli tested. The level of this protection increases from ∼15% in the wild type AB 1157 to ∼100% in the recA uvrA mutant AB 2480. It is suggested that DABCO protects against lethal events that can occur on macromolecules other than DNA such as the cell membrane. Results with added glycerol, as well as work in D2O solution, indicate that DABCO is more likely to be acting by scavenging radicals rather than by quenching 1O2. If 1O2 is a component of the sensitization afforded by oxygen, then it is unlikely to be formed in a hydrophilic environment in the cell. 相似文献
Salicylidene-o-aminobenzothiol and its 5-chloro and 5-bromo derivatives, dibasic tridentate Schiff bases, dervied from the condensation of o-aminothiol and Salicylaldehyde, 5-chloro salicylaldehyde and 5-bromo salicylaldehyde, were used for coordination with Zr(IV), Th(IV) and UO2(VI) metal inos. The I:I (metal-ligand) stoichiometry of these complexes is shown by elemental analysis and conductometric titrations. Molecular structure of these complexes are proved by Infra-red spectroscopy and thermogravimetric analysis. Magnetic susceptibility measurements of Zr(IV), Th(IV) and UO2(VI) complexes show their diamagnetic and octahedral geometry. Results show that all the complexes have solvent molecules in coordination with metal ion. 相似文献