Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Chromium Compounds”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,279 records · Page 71Linked to original sources
PubMed2002

Structural analysis of the solid amorphous binuclear complexes of iron(III) and aluminum(III) with chromium(III)-DTPA chelator using energy dispersive X-ray diffraction.

This paper is concerned with the structural data obtained for two amorphous binuclear complexes of iron(III) and aluminum(III) with chromium(III)-diethylentriaminepentaacetic acid (chromium(III)-DTPA, CrL(2)(-)) using the energy-dispersive X-ray diffraction technique. Fe(OH)CrL(H(2)O)(6) and Al(OH)CrL(H(2)O)(6) are binuclear complexes, the metals ions being bridged via oxygen atoms. The metal ions are all octahedrally coordinated.

Aluminum↗
PubMed2003

Aerobic oxidations catalyzed by chromium corroles.

Oxochromium(V) complexes of 5,10,15-tris(pentafluorophenyl)corrole and brominated derivatives oxygenate substrates (triphenylphosphine and norbornene) with concomitant production of chromium(III). Regeneration of CrVO by reaction of dioxygen with CrIII completes an aerobic catalytic cycle, with very large solvent effects; in acetonitrile, rapid initial turnovers observed initially are shut down by formation of CrIVO, while in toluene, THF, and methanol, relatively slow reactions are further inhibited by product formation.

Aerobiosis↗
PubMed2004

Fe/Cr- and Co/Cr-mediated catalytic asymmetric 2-haloallylations of aldehydes.

The first example to couple aldehydes and 3-bromo-2-halopropenes in a catalytic asymmetric manner is reported. The coupling reaction is effected by the use of a chiral sulfonamide-Cr complex (prepared in situ from 1d, CrBr3, Fe(III) or from Co(II), Et3N, and Mn), TMSCl, and 2,6-lutidine. The method reported here is operationally simple and scalable, furnishing 3-halohomoallylic alcohols with a synthetically useful level of enantiomeric excess.

Aldehydes↗
PubMed2001

A Nozaki-Hiyama-Kishi Ni(II)/Cr(II) coupling approach to the phomactins.

[reaction: see text] Through a unified synthetic strategy, appropriately functionalized bicyclic starting materials can be elaborated via Ni(II)/Cr(II) macrocylization to [9.3.1] bicycles. Elaboration of these core structures allows access to phomactin C/D analogues and establishes the first synthetic approach to phomactin A affording an intact octahydrochromene/macrocyclic ring system.

Animals↗
PubMed1999

Synthesis of (--)-lasubine(I) via a planar chiral [(eta6-arene)Cr(CO)3] complex.

Key steps of the synthesis of the Lythracaea alkaloid (--)-lasubine(I) are the formation of an enantiopure planar chiral arylaldehyde tricarbonylchromium complex and highly diastereoselective aza-Diels-Alder cycloaddition and intramolecular radical cyclization reactions to afford a quinolizidinone intermediate. Ketone reduction, desilylation, and decomplexation yield the enantiomerically pure product.

Alkaloids↗
PubMed2003

A total synthesis of (+/-)-phomactin A.

A total synthesis of the PAF antagonist phomactin A (1), isolated from the marine fungus Phoma sp. is described. The synthesis is based on a Cr(II)/Ni(II) macrocyclisation from the aldehyde vinyl iodide 14, leading to the key phomactatrienol intermediate 16a, followed by elaboration of 16a to the epoxyketone 21, which undergoes spontaneous pyran and hemiacetal ring formation to 1 on deprotection with DDQ.

Aldehydes↗
PubMed1977

On the bonding of FeO2 in hemoglobin and related dioxygen complexes.

The celebrated Fe(II)0(2) versus Fe(III) (02-) debate over the formal representation of the Fe02 moiety in hemoglobin can be resolved by consideration of the utility of each formalism. In the context of rationalizing the gross structural and electronic features of end-bound dioxygen, particularly in light of a new closely related chromium complex, the M(III)-(02-) formulation is both chemically reasonable and most useful. In conjunction with a qualitative molecular orbital overlap picture, the differing magnetic states of enc-bound M02 complexes and other geometrical features can be rationalized or predicted.

Chemical Phenomena↗
PubMedDate not supplied

Chemical characterization of sanding dust and methylene chloride usage in automotive refinishing: implications for occupational and environmental health.

Surface preparation activities conducted during automotive refinishing present several potential human health and environmental risks. This study examines the chemical composition of vehicle sanding dust and the prevalence of methylene chloride use as a basis for evaluating potential chemical exposures in the work environment, fugitive environmental releases, and take-home toxics. This article reports on the findings of (1) a statewide technology and work practices survey of 353 licensed auto body shops and (2) laboratory analyses of sanding dust representing more than 200 vehicles, 10 commercial body filler compounds, and work shirts worn during vehicle sanding while using nonventilated equipment. Survey data revealed that the majority of shops (78%) do not use ventilated sanding equipment, that most workers (55%) take their work clothes and shoes home at the end of the workday, and that 17% of the respondents used a methylene chloride-based paint stripper as an adjunct to mechanical sanding. Laboratory results showed that Pb, As, Cr, Mn, and Ni were present in the sanding dust at every facility tested. Lead concentrations in sanding dust were found to be highest at facilities that performed complete vehicle refinishing (range 770 to 7300 ppm) and at a collision repair shop that used a high-lead content body filler compound (1800 ppm). Hexavalent chromium also was found in two vocational high school paint dust samples at concentrations of 54 and 710 ppm. When total lead and chromium concentrations reached 7300 and 2300 ppm, respectively, facility sanding dust samples failed the U.S. Environmental Protection Agency's Toxicity Characteristic Leaching Procedure for hazardous waste. Metals found in the sanding dust also were present on the work shirts of technicians-ranging from 0.06 (Cd) to 81 (Mg) microg/inch2 of cloth-who sanded on paint without ventilated equipment. Results suggest that sanding dust and methylene chloride paint strippers used in vehicle resurfacing operations pose a potential hazard to human health and the environment.

Automobiles↗
PubMed2004

A study on dissolution properties of the sludges from Cr(VI) reduction-precipitation processes.

In this article, dissolution characteristics of Cr(VI) reduction-precipitation sludges in the solutions containing mineral acids, organic complexing materials or both are examined. For this purpose, the effects of pH, concentration of complex forming agent and contact time on dissolution of metals from two different sludges obtained by using sodium sulphite and ferrous sulphate as reducing agents are studied. In addition, pollution potentials of the sludges are determined by applying the toxicity tests of TCLP, SPLP, USEPA-1979, and USEPA-19X0. It was found that pH, contact time, concentration and type of complex forming substances are effective parameters on dissolution of metals from the sludges. In mineral acid solutions at pH 3, especially in the presence of organic complexing substances, chromium leached out from hydroxide sludges exceeds the concentration limits of USEPA for hazardous wastes. The amounts of chromium dissolved in the citric and ascorbic acid solutions and the amount of iron dissolved in the EDTA solution were found to be higher than in the other test solutions. Also, TCLP test shows that chromium hydroxide sludge obtained from sulphite reduction precipitation process of Cr(VI) is a potential hazardous solid. According to the results of this study, considering the probable presence of complexing agents in the disposal sites, toxicity test methods should be modified.

Carcinogens, Environmental↗
PubMed1996

Blood protein interactions with chromium surfaces.

Protein adsorption, contact activation, and complement activation were studied on thin evaporated films of chromium (Cr) in vitro. The surfaces were, prior to the experiments, cleaned in either ethanol and water, or in a basic peroxide solution (RCA standard clean 1, SC-1). Surface spectroscopic studies of the outermost oxides showed a significant reduction of carbon contaminants after washing in SC-1 but also suggested an increase in the oxidation state as compared with the ethanol-washed surfaces. In situ ellipsometry combined with antibody techniques was used to determine protein deposition and antibody binding onto surfaces after incubations in heparin plasma or in normal serum. Incubation times from 1 to 10 min in serum showed increased depositions of serum and antibodies to complement factor 3c (C3c) and was larger on ethanol-washed surfaces than on surfaces washed in SC-1. ELISA methods indicated increased amounts of iC3b in serum for both surfaces, but no presence of C3 convertases (C4d or Bb fractions). A low or transient complement activation via the classical pathway was indicated on ethanol washed Cr, since deposition of secondary antibodies to complement factor Iq (CIq) was observed only after short incubation times in serum. No procoagulant activity of Cr was indicated, since only low amounts of antibodies to factor XII (F XII), prekallikrein (PKK), and high molecular weight kiniogen (HMWK) bound to the surfaces after incubations in heparin plasma. These results were confirmed using a colorimetric assay where the relative amounts of free plasma kallikrein was assessed using a chromogenic substrate, H-D-Pro-Phe-Arg-pNA (S-2302).

Adsorption↗
PubMed2006

Crystalline hydrous ferric oxide: an adsorbent for chromium(VI)-contaminated industrial wastewater treatment.

Synthetic crystalline hydrous ferric oxide (CHFO) (particle size 0.14 to 0.29 mm) has been used systematically for adsorptive chromium(VI) removal from contaminated water. Batch experiments were performed as a function of pH, contact time, solute concentration, and regeneration of adsorbents. Column experiments were performed for breakthrough points in the presence and absence of other ions and treatment of industrial effluent. The optimum pH range was 2.0 to 4.0. The adsorption kinetic data could be described well by both second-order and pseudo-first-order models. The isotherm adsorption data at 30 +/- 2 degrees C obeyed the Langmuir model best. The monolayer adsorption capacity was 35.7 mg/g. Chromium(VI)-rich CHFO could be regenerated up to 89 +/- 1% with 2.0 M sodium hydroxide. Regenerated column reuse showed a decrease (10 to 12%) in breakthrough capacity. Finally, the CHFO- (dried at 300 degrees C) packed column was used for the recovery (98.5 +/- 1.0%) of chromium(VI) from contaminated industrial waste effluent of Hindustan Motor Limited (Hooghly, West Bengal, India).

Adsorption↗
PubMed1986

[Prevention of occupational carcinogens: perspectives opened by the evaluation of risks and preventive actions].

The first part of the review deals with the present situation in terms of prevention against potential carcinogenic substances in France. A significant effort should be devoted to the measurement of contaminants--not only carcinogenic substances--in the workplace. This is a prerequisite for setting a data base in terms of potential occupational risk. Moreover gaps exist also as far as the definition of the technical means aimed at the reduction of risk is concerned. These conclusions put into light the importance of the contribution that "industrial hygienists" would bring in France. In the second part of the review, the methodological content of the risk assessment and risk management procedures is described and illustrated. Risk assessment of carcinogens deals: with the identification of potential carcinogens through epidemiology, animal bio-assays and short term tests; with the quantitative estimation of the magnitude of the potential carcinogenic risk among the exposed workers. It appears necessary to carry out systematic surveys of the number of workers exposed to the carcinogenic substances. The risk assessment procedure is applied to 5 substances BCME, MOCA, Acrylonitrile, Chromium, Nickel and some compounds of these metals. The number of potential excess cancers related to a unit lifelong exposure to Nickel compounds is estimated. This requires exposure-response models which are critically analysed. Risk management is devoted to the choice of primary health care policies. The methodology of risk management consists of: identifying various control policies; quantitative estimation of their efficiency--indicators of the efficiency are discussed--and of their cost; choice among these policies with the help of a cost-effectiveness analysis when necessary. The procedure is illustrated in the case of Acrylonitrile control in a facility.

Carcinogens↗
PubMed1985

The mechanism and specificity of iron transport in Rhodotorula pilimanae probed by synthetic analogs of rhodotorulic acid.

The yeast Rhodotorula pilimanae produces the dihydroxamate siderophore rhodotorulic acid (RA) in prodigious amounts when starved for iron. Synthetic dihydroxamate analogs of RA have been prepared in which the diketopiperazine ring of RA is replaced by a simple chain of n methylene groups. It is found that R. pilimanae is able to accumulate iron using these achiral complexes, as well as from simple monohydroxamate analogs, at rates comparable to those of RA. While the Fe2RA3 complex does not enter the cell, there is a receptor system whose geometric requirements for siderophore recognition have been probed using analogs. In contrast to mono- or dihydroxamate ligands, the trihydroxamate siderophores such as ferrioxamine B are completely ineffective at delivering iron to R. pilimanae. This is ascribed to the greater stability of these complexes, which blocks release of the Fe(III) in a ligand exchange process that is required for uptake. To explore whether this ligand exchange involves redox catalysis, Ga(III) was substituted for Fe(III). The gallium was taken up at rates near those of iron and were also energy-dependent, as determined by metabolic inhibition with KCN.

Biological Transport, Active↗