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PubMed2006

Physical, chemical and environmental properties of selected chemical alternatives for the pre-plant use of methyl bromide as soil fumigant.

Production and use of methyl bromide, a soil fumigant, are being restricted because of this chemical's deleterious effects on stratospheric ozone concentrations. Several products, some of which are currently used as soil fumigants, are being considered as possible replacements for methyl bromide, alone and in various combinations. Among these, 1,3-dichloropropene, methyl isothiocyanate generators such as metam-sodium, and chloropicrin are currently registered, while others such as methyl iodide and sodium azide are at different stages of the registration process. This review examines physicochemical properties, environmental fate, and metabolism of the various potential methyl bromide replacement products.

Agriculture↗
PubMed1994

Magnetometric measurements of macrophage activity in the liver after administration of different perfluorochemicals.

The activity of liver macrophages was evaluated using a magnetometric method after administration of different perfluorochemicals. Following treatment with perfluoroctylbromide a significant shorter time period of diminished macrophage activity was found compared with a mixture of perfluorodecalin and perfluorotripropylamine. Results obtained with the magnetometric method on liver macrophages were more sensitive compared with those of colloidal carbon clearance of total body RES.

Animals↗
PubMed1991

Synthesis, characterization and radiolabelling of 2-[6-(4-bromophenoxy)hexyl]oxirane-2-carboxylic acid.

A method is described for the synthesis, purification and radiolabelling of 2-[6-(4-bromophenoxy)hexyl]-oxirane-2-carboxylic acid. For the synthesis of this new agent, 6-(4-bromophenoxy)hexylbromide (1), synthesized by the treatment of 4-bromophenol with 1,6-dibromohexane under basic conditions, was converted to diethyl 6-(4-bromophenoxy)hexylmalonate (2), which, on alkaline hydrolysis, yielded ethyl 6-(4-bromophenoxy)hexylmalonate (3). Ethyl 8-(4-bromophenoxy)-2-methyleneoctanoate (4), prepared from the monoester (3), was oxidized with m-chloroperbenzoic acid to yield ethyl 2-[6-(4-bromophenoxy)-hexyl]oxirane-2-carboxylate (5). The method of radiolabelling, based on the Cu(I)Cl-assisted nucleophilic exchange reaction, resulted in regioselective radiobromination with a 45% radiochemical yield.

Bromine Radioisotopes↗
PubMed2005

Speciation and biosynthetic variation in four dictyoceratid sponges and their cyanobacterial symbiont, Oscillatoria spongeliae.

Four species of marine sponges (Phylum Porifera, Order Dictyoceratida), which contain the filamentous cyanobacterial symbiont Oscillatoria spongeliae, were collected from four locations in Palau. The halogenated natural products associated with the symbiont were characterized from each sample, revealing that each species contained either chlorinated peptides, brominated diphenyl ethers, or no halogenated compounds. Analysis of the host sponges and the symbionts indicated that each species of sponge contained a distinct strain of morphologically similar cyanobacteria. Although cospeciation may be present in this group, we have identified that at least one host switching event has occurred in this symbiosis. Only the strain of O. spongeliae in the sponge containing the chlorinated compounds possessed genes involved in the biosynthesis of chlorinated leucine precursors, indicating that the chemical variation observed in these animals has a genetic foundation.

Animals↗
PubMed2005

Henry's law constants and mass transfer coefficients for methyl bromide and 1,3-dichloropropene applied to Florida sandy field soil.

Methyl bromide, a pre-emergent soil fumigant, is scheduled to be phased out in the US by 2005, with exceptions for critical use. Comparison of some of the physical constants related to distribution and retention for methyl bromide (MBr) to other fumigants yields a useful quantification of possible alternatives. In this study, the atmospheric and subsurface dissipation of methyl bromide as well as (Z)- and (E)-1,3-dichloropropene (1,3-D) isomers in Telone II were examined. The Henry's law constants of the three chemicals at soil temperature and their mass transfer coefficients for movement through an agricultural mulch of UV-resistant, high-density polyethylene (PE) were evaluated using field data. At the soil temperature of 16.4 degrees C, calculated Henry's law constant gave a fumigant ranking of MBr (0.21)>>(Z)-1,3-D (0.041)>(E)-1,3-D (0.027). Since rapid subsurface distribution of a fumigant is highly dependent on the amount in the gas phase, the greater value for Henry's law constant implies faster distribution throughout the soil. After distribution through the soil, retention of the fumigant becomes imperative. Calculation of the fumigant's mass transfer coefficients through PE from field data gave a ranking of the three chemicals: MBr (1.08 cm/h)<(E)-1,3-D (3.25 cm/h)<(Z)-1,3-D (4.13 cm/h). With mass transfer coefficients of this magnitude, it was concluded that PE film was an inadequate barrier for retaining these fumigants in an agricultural setting.

Agriculture↗
PubMed2005

Flame retardants, surfactants and organotins in sediment and mysid shrimp of the Scheldt estuary (The Netherlands).

Sediment and mysids from the Scheldt estuary, one of the largest and most polluted estuaries in Western Europe, were analyzed for a number of contaminants that have been shown to possess endocrine-disrupting activity, i.e. organotins, polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBPA), nonylphenol ethoxylates (NPE) and transformation products, nonylphenol (NP) and nonylphenol ether carboxylates (NPEC). In addition, in vitro estrogenic and androgenic potencies of water and sediment extracts were determined. Total organotin concentrations ranged from 84 to 348 ng/g dw in sediment and 1110 to 1370 ng/g dw in mysid. Total PBDE (excluding BDE-209) concentrations ranged from 14 to 22 ng/g dw in sediment and from 1765 to 2962 ng/g lipid in mysid. High concentrations of BDE-209 (240-1650 ng/g dw) were detected in sediment and mysid (269-600 ng/g lipid). Total HBCD concentrations in sediment and mysid were 14-71 ng/g dw and 562-727 ng/g lipid, respectively. Total NPE concentrations in sediment were 1422 ng/g dw, 1222 ng/g dw for NP and 80 ng/g dw for NPEC and ranged from 430 to 1119 ng/g dw for total NPE and from 206 to 435 ng/g dw for NP in mysid. Significant estrogenic potency, as analyzed using the yeast estrogen assay, was detected in sediment and water samples from the Scheldt estuary, but no androgenic activity was found. This study is the first to report high levels of endocrine disruptors in estuarine mysids.

Animals↗
PubMed2006

Bischromophoric styrylpyridinium dyes. Spectroscopic properties of 1,3-bis-[4-(p-N,N-dialkylaminostyryl)pyridinyl]propane dibromides.

The photophysical properties of newly synthesized bischromophoric solvatochromic stilbazolium dyes, 1,3-bis-[4-(p-N,N-dialkylaminostyryl)pyridinyl]propane dibromides (C1-C9), were studied in a series of solvents and their spectroscopic properties were compared with structurally related, monochromophoric styrylpyridinium dyes (SP1-SP9). The position of the UV-vis absorption spectra maximum of novel dyes is only slightly solvent polarity dependent in contrast to the fluorescence spectra that show pronounced solvatochromic effect demonstrated by a large Stokes shifts. The influence of the solvent on absorption and emission spectra, and the solvatochromic properties observed for both ground and first excited states for all the dyes were used for the evaluation of their excited state dipole moments. The ground state dipole moments of both mono- and bischromophoric dyes were established by applying ab initio calculations. The calculations and measurements unexpectedly show that the bischromophoric dyes are characterized by ground state dipole moments being equal to about half of that characterizing their monomeric equivalents, while the excited state dipole moments of bischromophoric dyes are about 10-25% higher in comparison to their monomeric equivalents.

Fluorescent Dyes↗
PubMed2001

Polyhalogenated homosesquiterpenic fatty acids from Plocamium cartilagineum.

We describe the composition of novel polyhalogenated homosesquiterpenic acids from the red alga Plocamium collected during summer on Maltese Islands and Corsica. The compounds, predominantly derivatives with unique groups (bromine, chlorine, and diene), were identified by means of 1H and 13C NMR, MS, IR and UV spectra.

Biological Factors↗
PubMed2002

Debromination of hexabromobenzene by its co-grinding with CaO.

A hexabromobenzene (HBB, C6Br6) powder was subjected to co-grinding with excess CaO powder in air using a planetary ball mill to investigate mechanochemical debromination of the HBB sample. The reaction proceeds smoothly with an increase in both grinding time and molar ratio of CaO addition. The co-grinding enables us to debrominate HBB, forming CaBr2, C and CaCO3 besides excess CaO in the product. CaBr2 in the product tends to absorb moisture from the atmosphere to form CaBr2 x nH2O. The reaction yield is quantitatively evaluated by measuring the amount of water-soluble bromide through water washing and the amount of unreacted HBB through toluene washing. It is found that almost 100% of debromination is achieved by 6 h grinding with the molar ratio kept constant at 2:1. Radicals are detected in the ground products, possibly due to rupture in the covalent bonds of C-C and C-Br in HBB.

Bromine↗
PubMed1999

Encephalomyeloradiculoneuropathy following exposure to an industrial solvent.

A 19-year-old male developed complaints including weakness of the lower extremities and right hand, numbness, dysphagia and urinary difficulties following a 2 month exposure to an industrial solvent constituted mainly of 1-bromopropane, but also containing butylene oxide, 1,3 dioxolane, nitromethane, and other components. Nerve conduction studies revealed evidence of a primary, symmetric demyelinating polyneuropathy. Evidence of CNS involvement came from gadolinium enhanced MRI scans of the brain, showing patchy areas of increased T2 signal in the periventricular white matter, similar scans of the spinal cord revealing root enhancement at several lumbar levels, and SSEP studies. The patient's symptoms had started to resolve following the discontinuation of the exposure, before he was lost to follow-up. Similar findings have been reported following 1-bromopropane exposure in rats. I hypothesize that this patient's symptoms may have been due to 1-bromopropane-induced neurotoxicity.

Adult↗
PubMed2003

Room-temperature Stille cross-couplings of alkenyltin reagents and functionalized alkyl bromides that possess beta hydrogens.

This communication describes a significant expansion in the scope of Stille reactions of Csp3-X electrophiles, specifically, that Pd/P(t-Bu)2Me catalyzes the room-temperature cross-coupling of a variety of functionalized, beta-hydrogen-containing alkyl bromides with an array of alkenyltin reagents. The structure of the phosphine (P(t-Bu)2Me) is well suited for facilitating oxidative addition and avoiding beta-hydride elimination, while the fluoride serves to activate the tin reagent for efficient transmetalation.

Alkenes↗
PubMed2005

Catalytic enantioselective Negishi reactions of racemic secondary benzylic halides.

This report describes the first enantioselective cross-couplings of racemic secondary benzylic halides, specifically, nickel-catalyzed Negishi reactions of bromides and chlorides. The catalyst components are commercially available and air-stable, and the reaction is not highly oxygen- or moisture-sensitive (it can be set up in the air). The method has been applied to the catalytic enantioselective synthesis of intermediates employed by others in the generation of bioactive compounds (e.g., trikentrin A and an androgen receptor agonist).

Alkylation↗
PubMed2006

Palladium-catalyzed intermolecular alpha-arylation of zinc amide enolates under mild conditions.

The intermolecular alpha-arylation and vinylation of amides by palladium-catalyzed coupling of aryl bromides and vinyl bromides with zinc enolates of amides is reported. Reactions of three different types of zinc enolates have been developed. The reactions of aryl halides occur in high yields with isolated Reformatsky reagents generated from alpha-bromo amides, with Reformatsky reagents generated in situ from alpha-bromo amides, and with zinc enolates generated by quenching lithium enolates of amides with zinc chloride. This use of zinc enolates, instead of alkali metal enolates, greatly expands the scope of amide arylation. The reactions occur at room temperature or 70 degrees C with bromoarenes containing cyano, nitro, ester, keto, fluoro, hydroxyl, or amino functionality and with bromopyridines. Moreover, the reaction has been developed with morpholine amides, the products of which are precursors to ketones and aldehydes. The arylation of zinc enolates of amides was conducted with catalysts bearing the hindered pentaphenylferrocenyl di-tert-butylphosphine (Q-phos) or the highly reactive, dimeric, Pd(I) complex [[P(t-Bu)3]PdBr]2.

Amides↗