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BACKGROUND: Organohalogen compounds (OHCs) are known to have neurotoxic effects on the developing brain. OBJECTIVE: We investigated the influence of prenatal exposure to OHCs, including brominated flame retardants, on motor, [...]

We describe a novel radio frequency ion trap mass analyzer based on toroidal trapping geometry and micro-fabrication technology. The device, called the halo ion trap, consists of two parallel ceramic plates, the facing surfaces of which are imprinted with sets of concentric ring electrodes. Radii of the imprinted rings range from 5 to 12 mm, and the spacing between the plates is 4 mm. Unlike conventional ion traps, in which hyperbolic metal electrodes establish equipotential boundary conditions, electric fields in the halo ion trap are established by applying different radio frequency potentials to each ring. The potential on each ring can be independently optimized to provide the best trapping field. The halo ion trap features an open structure, allowing easy access for in situ ionization. The toroidal geometry provides a large trapping and analyzing volume, increasing the number of ions that can be stored and reducing the effects of space-charge on mass analysis. Preliminary mass spectra show resolution (m/[DELTA]m) of 60-75 when the trap is operated at 1.9 MHz and 500 [V.sub.p-p].

Water-, mud-, gas-, and petroleum-bearing seeps are part of the Salton Sea geothermal system (SSGS) in Southern California. Seeps in the Davis-Schrimpf seep field (~14,000 [m.sup.2]) show considerable variations in water temperature, pH, density, and solute content. Water-rich springs have low densities (98 vol%). Halogen geochemistry of the waters indicates that mixing of deep and shallow waters occurs and that near-surface dissolution of halite may overprint the original fluid compositions. Carbon isotopic analyses suggest that hydrocarbon seep gases have a thermogenic origin. This hypothesis is supported by the presence of petroleum in a water-dominated spring, composed of 53 % saturated compounds, 35 % aromatics, and 12 % polar compounds. The abundance of polyaromatic hydrocarbons and immature biomarkers suggests a hydrothermal formation of the petroleum, making the SSGS a relevant analogue to less accessible hydrothermal seep systems, e.g., the Guaymas Basin in the Gulf of California. Keywords: Salton Sea, hydrothermal seeps, hydrocarbons, halogen geochemistry, geothermal, petroleum.

The potential of gas chromatography coupled to tandem mass spectrometry (GC/MS/MS) with a triple quadrupole analyzer (QqQ) has been investigated for the accurate and sensitive determination of xenoestrogens in human breast tissues. Special emphasis has been given to the confirmation of the identity of compounds detected in the samples analyzed in order to avoid the reporting of false positives. The work has been focused on the determination of ~30 organochlodne compounds (PCBs and pesticides) and organobromine compounds (polybrominated diphenyl ethers) in adipose breast tissue and in tumoral fragment. Analytes were extracted by dissolving the samples in hexane, and the extracts were purified by automated normal-phase HPLC prior to GC/MS/MS analysis. Three isotopically labeled standards were added before extraction as surrogates for the quality control of the analyses. Accuracy and precision were evaluated by means of recovery experiments using adipose breast tissue spiked at three concentration levels, with satisfactory results for most analytes. The excellent selectivity and sensitity of QqQ in selected reaction monitoring mode allowed us satisfactory quantification and confirmation at levels as low as 5-25 ng/g, i.e., the lowest concentration level for which the method was fully validated. Two MS/MS transitions were selected for each analyte, using the concentration ratio obtained from them as a confirmatory parameter. The developed methodology was applied to the analysis of 51 breast samples (26 adipose tissues and 25 tumoral fragments), giving as a result the detection and confirmation of several organochlorine compounds in both types of samples. Due to its adequate analytical characteristics, the optimized method fits with the requirements of accurate quantification and reliable confirmation of the identity of compounds detected according to the most recent European Guidelines. As an ultimate unequivocal confirmation, several selected samples were reanalyzed by gas chromatography coupled to mass spectrometry with a time-of-flight (TOF) analyzer. Confirmation of analytes present at higher concentrations was successful with mass error less than 5 mDa. However, confirmation by TOF MS was not possible al low concentrations (i.e., at the few ng/g level) as a consequence of its lower sensitivity compared with that of triple quadrupole in selected reaction monitoring mode.

The phosphoramidite building blocks were used to synthesize oligonucleotides containing 2'-deoxyisoguanosine, 7-deaza-2'-deoxyisoguanosine, and its 7-halogenated derivatives on solid phase. Studies on the hybridization properties of oligonucleotides found that the 7-halogenated nucleoside analogues enhance the duplex stability significantly in both parallel (ps) and antiparallel (aps) DNA.

Newly discovered biogenic organo halogens with an emphasis on the biologically active examples from marine organisms, bacteria, terrestrial plants and higher life forms, including humans, are focused. Organohalogen compounds represent a valuable and expanding class of natural products, in many cases boasting exceptional biological activity.

A femtosecond laser-induced clean fluorescence technique was explored as a means to monitor halogenated alkanes in the atmosphere. Characteristic difluorocarbene radical (C[F.sub.2]) fluorescence in the UV-vis can be generated inside a femtosecond laser-induced filament for different halocarbons. We show that, due to different dissociation and excitation kinetics leading to fluorescence emission, it is possible to temporally resolve the characteristic fluorescence of C[F.sub.2]-containing halocarbons from that of background species, therefore enhancing the signal-to-noise ratio. Laboratory-scale experiments demonstrate the potential use of femtosecond laser-induced clean fluorescence for the remote sensing of halocarbons in the atmosphere. The combination of this detection strategy with LIDAR could allow the long-range monitoring of several atmospheric species with a single laser source, eventually leading to a better understanding of chemical and dynamic processes affecting global warming, ozone loss, tropospheric pollution, and weather prediction.

The symmetry groups of two nonrigid molecules are discussed relative to a part of a paper by H.C. Longuet-Higgins with the goal of resolving an apparent self-contradiction. An obstacle to fuller, and no doubt timely, incorporation of the ideas into the literature should thereby be removed. A group theory of nonrigid floppy molecules exists. This is relevant to various important topics in chemistry. Topics include the case of BF(sub.2)CH(sub.3) and the case of N(sub.2)H(sub.4).

Chlorine kinetic isotope effects were observed on dehalogenation catalyzed by haloalkane dehalogenase from Xanthobacter autotrophicus GJ10, in the 1.0045 plus or minus 0.0004 range for 1,2 dichloroethane and 1.0066 plus or minus 0.0004 range for 1 chlorobutane.

A research report discusses the development of a new hazardous index to measure semi- and nonvolatile organic compounds in order to observe the release of flue gas.

Many genera belonging to the Proteobacteria can degrade many different halobenzoates and these bacteria are common in soil. Halogenated aromatic compounds are common pollutants, since they are used as herbicides, insecticides, solvents, fire retardants, and lubricants.

The article discusses the kinetic reaction of hydroxyl radicals when exposed to halomethanes.

Researchers from the University of Newcastle, New South Wales conducted experiments on the gas-phase hydrogen dehalogenation of halon 301 (CBrF3) in an alumina reactor.

Research designed to demonstrate the mechanism and the kinetics of the electron attachment in the mixture of some halomethanes and nitrogen is presented. It is shown that CHF3 and CCIF3 in the mixture with nitrogen accept electrons as individual molecules and as van der Waals complexes.

The bacterium that causes tuberculosis has three different genes that code for enzymes that can break down synthetic haloalkanes. The amino acid sequence of these enzymes in other microorganisms was known and researchers found the same sequence in the genome of Mycobacterium tuberculosis, which was published in 1998.

Convergent solution-phase combinatorial synthesis is discussed relative to increasing diversity via rigid biaryl and diarylacetylene couplings. Solution-phase synthesis of iminodiacetic acid diamide libraries linked to aryl iodides and palladium-catalyzed dimerization has been studied. Mixtures with 64,980 components have been produced in four steps from N-BOC-iminodiacetic acid anhydride and 21 starting materials that are readily available. Sequential Stille couplings and biaryl formation are used in the synthesis.

A reconstruction back to the late 19th century of atmospheric concentrations of halons, chlorofluorocarbons, sulphur hexafluoride and persistent chlorocarbon solvents gives results consistent with atmospheric histories taken from anthropogenic emission rates and known atmospheric lifetimes. This research used samples of air collected from firn at the South Pole and Siple Dome in Antarctica and at Tunu in Greenland. It has been possible to refine halocarbon histories and produce experimental evidence about their pre-anthropogenic concentrations.

The rate coefficients for the gas-phase reaction of hydroxyl radicals with CH2ClCF2Cl and CH2ClCF3 over an extended temperature range were studied. A laser photolysis/laser induced fluorescence technique under slow flow conditions at a total pressure of 740 + 10 Torr was used for the measurements. The results showed new lower temperature data which was intermediate to previous measurements.

Electron spin resonance (ESR) spectroscopy and electron nuclear double resonance resonance (ENDOR) spectroscopy are used to examine the radical cations of methyl-substituted benzene generated in halocarbon matrices by X-ray irradiation at 77 K. Results of the ESR and ENDOR spectroscopy show that radical cations are dominated by large axially symmetric hyperfine splitting due to methyl-group protons. Experimental and theoretical evidence also showed that radical cations of toluene and p-xylene had a more stable type of state than o-xylene and m-xylene.

The reaction-path dynamics and dual-level approaches were used to perform a dynamic and kinetic study of the CH3F + OH title reaction and to trace the reaction-path for this process. This reaction is important in combustion and atmospheric chemistry and presents a theoretical challenge due to the flat potential energy surface and an experimental challenge due to the curvature in the Arrhenius plot which remains an open question. Results indicate that tunneling plays an important role in this reaction and, therefore, a noticeable curvature can be expected in the Arrhenius plot.

An experiment relating chemical reactions involving halomethylenecyclobutanes was conducted to establish the effects the nature of the halogen exerts on the mechanistic course of the rearrangement of halomethyenecyclobutanes to 1-halocyclopentenes. The study also aimed to discover whether or not fluorines placed beta to the negative charge facilitate the rearrangement process in this particular reaction. Results of the experiment are discussed.

Reductive dechlorination of chlorinated ethenes by anaerobic bacteria is surmised to follow a pathway wherein chloroalkylcobalamin complexes are reduced to form chlorinated ethene intermediates. The degradation is catalyzed by vitamin B12 and titanium citrate which effects a homolytic cleavage and titanium-catalyzed elimination reaction. This alternative pathway can be manipulated to reduce the release of undesirable intermediates such as vinyl chloride.

The ability of methanogens, such as Methanosarcina barkeri, M. thermophila and Methanosaeta concillii, in dechlorinating carbon tetrachloride and chloroform in an iron-rich medium was shown to be dependent on the availability of elemental hydrogen. Elemental hydrogen acted as an electron donor in the dechlorination process, which is effected in the excreted biomolecule specifically produced to exploit this process to support microbial metabolism.

A detailed, systematic study of the halocarbonyl-w(II) complexes, LWX(CO)3 and LWX(CO)2 is presented. Convenient syntheses, physical and spectroscopic data and the X-ray crystal structure of the closely related complex L(super Pr)WI(CO)3 are reported. The 3:3:1 carbonyl-capped octahedral structure of L(super Pr)WI(CO)3 is compared with the structure of (HB(pz)3)MoBr(CO)3. Furthermore, the synthesis and characterization of NEt4L(super Br)W(CO)3, L(super Br)WBr-(CO)3, L(super Br)WBr(CO)2 and L(super Br)WB(MeCN)(CO) are examined to clarify observed ligand 4-bromination of NEt4(LW-(CO))3 by Br2.

The performance of a laser-induced breakdown spectroscopy (LIBS) in the identification of candidate halogenated hydrocarbon (halon) replacement compounds is examined. Specifically, the LIBS method is tested in an extremely hostile fire suppression testing environment. Results confirm the effectiveness of LIBS as an in situ and real time measurement tool for halons during full-scale fire suppression.

A new gas chromatographic method developed to quantitatively determine important atmospheric halocarbons is described. Target compounds include replacement CFCs, chlorinated solvents, and biosynthesized (naturally produced) organohalogens, all trace gases in the atmosphere at concentrations ranging from 0.1 to 600 pptv (where pptv = 1 part in [10.sup.-12] by volume). A combination of ultralow concentrations and relatively small electron attachment cross sections renders these compounds very difficult to routinely measure in the background air typical of remote atmospheric monitoring stations. Detection is achieved by preconcentration of a 200-mL air sample using an adsorbent-filled microtrap and enhancement of electron capture detector response by oxygen doping one of two detectors connected in series. Oxygen doping specifically targets halocarbons with relatively poor electron attachment rate coefficients. The work described here details construction of a novel analytical system, laboratory trials, and optimization followed by an extended field campaign at a remote atmospheric monitoring station, Mace Head, Ireland. A calibration standard or ambient air sample was acquired every hour using a cyclic, automated procedure without employing cryogenic preconcentration or refocusing. Overall precision of the analytical method for the target compounds is between 0.3 and 1.5%.

Single-pulse shock-tube technique was utilized to investigate the pyrolysis of CF3CHFCF3 in dilute mixtures in argon. The reaction produced several products such as C2F6, CF2=CHF, C2F4, C3F6, cyclo-C3F6 and CF3CHFCF2H. Isomers of C4F8 and traces of CF3H, CF4, C2F5H, C3F8 and C4F6 were also detected. A detailed kinetic reaction scheme showed that the major initiation reaction was the C-C bond fission reaction. Reaction-path analysis also showed that the abstraction of the secondary H atom by F was found to be the next most important destruction route.

Microbiological research shows that sulfate, sulfite and thiosulfate inhibits growth in the microorganism Desulfomonile tiedjei via a number of physiological mechanisms, all of which affect the enzyme reductive dehalogenation and involve sulfur oxyanions. Evidence suggests that sulfur oxyanions act as preferred electron acceptors and negatively influence dehalogenation activity via active aryl dehalogenase level control.

DL-2-haloacid dehydrogenase from Pseudomonas sp. strain 113 (DL-DEX) is a hydrolic dehalogenase catalyst which acts on the chiral of the acid substrate and uses both enantiomers as equal substrates. DL-DEX gene encoder isolation and sequencing were done to determine the structural make-up but no similarity between the DL-DEX and L-DEX was detected. Each enantiomer of 2-chloropropionate competitively inhibits the enzymatic dehalogenation of each other, suggesting that DL-DEX has a single common catalytic site for both enantiomers.

A C-6 protonated chrysenium ion was synthesized from the CO-protonation of 6-acetylchrisene. Nuclear magnetic resonance analysis of the resulting chrysenium cations, CO-protonated 6-acetylchrysene and methanochrysenium ions indicated the presence of long range C-H couplings and spectral variations that were induced by variations in the halogen substituents. Furthermore, the presence of halogen substituents in the C-6 carbon unit did not alter the mode of charge delocalization in the resulting arenium ions.

The absolute heats of formation for phenylcarbene (PhCH) and vinylcarbene (CH2=CHCH) as well as the disassociation energies inherent in the lysis of halide ions from alpha-halocarbanion to form a carbene with a triplet ground state were determined through utilization of afterglow-triple quadruple flow apparatus. Results indicated that the disassociation of halide from the activated halobenzyl anions occurs without the exchange of heat to yield the triple state of the product.

The reproductive problems arising in a variety of fish-eating mammals and birds in Saginaw River, MI are conjectured to have been caused by high concentrations of planar, halogenated hydrocarbons. In order to analyze the the dioxin-like toxicity in the river and to estimate its concentrations, researchers compared resultant data from an experiment using a semipermeable membrane device, an assessment of bioconcentrations in co-exposed, caged channel catfish, and sediment-based water sampling method.

INTRODUCTION The occurrence of organohalogens in nature is generally ascribed to anthropogenic activities (6). However, over 2600 different natural halogenated compounds have been identified (66, 67), and a large pool [...]

Oximes were oxidized to the corresponding halonitro products and ketones in aqueous solutions in the presence of halide ions, hydrogen peroxide and chloroperoxidase hemoprotein isolated from the fungus Caldaromyces fumago (CPO). Experimental observations of the conversion, which were performed in aqueous solutions, underscored the direct and limited participation of the enzyme in the reaction and the presence of a competitive nonenzymatic oxime oxidation/halogenation pathway.

The reaction of Pt(PiPr3)3 with SO2 produced (PiPr3)2Pt(SO2) (1), isolated in 93% yield. The addition of (H(OEt(sub 2))2)(super +)(BAr(sub f)=B(3,5-(CF(sub 3)(sub 2)C(sub 6)H(sub 3))(sub 4)) to 1 in ether at -78 degrees C produced the solvent complex trans-((PiPr(sub 3))(sub 2))Pt(H)(OEt(sub 2)))BAr(sub f) (2) in 85% isolated yield. The dichloromethane complex trans-((PiPr(sub 3))(sub 2)Pt(H)(eta(super 1)-ClCH(sub 2)Cl))BAr(sub f) (3) was isolated in 80% yield by the recrystallization of 2 from CH2Cl2/hexane. The reaction of 2 or 3 with iodo- or bromobenzene resulted in the isolation of the haloarene compounds trans-((PiPr(sub 3))(sub 2)Pt(H)(eta(super 1)-XPh))BAr(sub f), where X = I (87% yield) or Br (60% yield).

The local elimination of halocarbons from air by high-power microwave sources is studied. The destruction of halocarbons can be due to free electrons produced in a freely localized discharge started in the air by a focused microwave beam. After rapid cooling, the electrons can link with halocarbon molecules and destroy them. Operating regimes and their efficiencies are examined and the corresponding parameters of microwave sources are specified.

Laser flash photolysis at temperatures of 170-230 K was employed to examine the intramolecular reactions of alpha-methylbenzylchlorodiazirine, n-propylchlorodiazirine and isopropylchlorodiazirine in isooctane. The results, which were obtained by measuring the amplitude of pyridinium ylide absorption as a function of the amount of pyridine, quantitatively showed the 'by-stander effect' of alkyl substituents on the carbon atom in the alpha position at the carbene center of the halocarbons.

The dehalogenation of organic compounds using iron metal was investigated by measuring the kinetics of the degradation process and evaluating kinetic data using a consistent kinetic model. The results revealed that degradation rates were affected by experimental conditions. Correlation analysis showed a more rapid dechlorination at saturated carbon centers than at unsaturated carbons. Higher degrees of halogenation also resulted in the significant reduction of the compounds.

The nucleophilic substitution of cyclic thionylphosphazenes, (NSOX(NPCl2)2), with phenoxide, trifluoroethoxide, and butoxide is regioselective at the phosphorus centers. The 31P- and 19F-NMR spectra show the formation of a single isomer of mono-, di- and tri-substituted cyclothionylphosphazene. The substitution occurs through a vicinal pathway. In a substitutional control of the reaction using phenoxide and butoxide as nucleophiles, the order of reactivity is PCl2 > PCl(OR) > SOX where X = Cl, F.

Arylaluminum halides, hydride halides, and their THF adducts are prepared using new reaction pathways. Reaction between ((THF)2LiH3AlMes*)2, Mes* = 2,4,6-t-Bu3C6H(super -)(sub 2), and 6 equivalents of Me3SiCl leads to Mes*AlCl2(THF) in high yield. Synthesis of Mes*AlCl2(THF) by another route involves the reaction of (THF)2LiMes* with two equivalents of AlCl3 in toluene. Pyrolysis of Mes*AlCl2(THF) gives the THF free compound, Mes*AlCl2. A 1:1 mixture of Mes*Li(THF)2 and LiAlH4 reacts with two equivalents of Me3SiCl to yield Mes*Al(H)Cl(THF) which on sublimation gives Mes*Al(H)Cl.

Haloalkanes are broken down into halides and alkanes through a reaction that is catalyzed by haloalkane dehalogenase. The catalytic mechanism revolves around the hydrolysis of a covalent alkyl-enzyme complex that is formed during the reaction. Evidence shows that halide release during the reaction is preceded by a slow isomerization that results in a conformational change in the cap domain.

Kovats retention indices of 97 halocarbons related to research on alternative refrigerants, propellants, foaming agents, and blowing agents have been measured on a packed column stationary phase consisting of a 5% (mass/mass) coating of a low molecular weight polymer of hexafluoropropylene epoxide on graphitized carbon black. The measurements on each fluid have been made at four temperatures, and the thermal dependence of the indices has been modeled with appropriate equations. The modeled values are suitable for the identification of these compounds by gas chromatography on both laboratory and field instrumentation. The values are also useful for the optimization of more sophisticated analyses needed in specific situations. The results indicate that the stationary phase chosen will provide separation of nearly all the fluids of interest. Moreover, we show that there is sufficient spread in the retention index values to facilitate fluid identification. The measurements also appear to fit a qualitative triangular property diagram that has been useful for classifying alternative refrigerant fluids and related compounds.

The spectral characteristics and association constants of the charge transfer complexes formed by tetracyanoethylene with organohalide donors in dichloromethane have been derived. The data, which showed the influence of intramolecular conjugative and inductive effects on the charge transfer energies, revealed that the coupling of tetracyanoethylene with haloalkanes or halobenzenes results in weak pi complexes of dichlorobenzenes, dibromobenzenes, diiodobenzenes and halotoluenes.

The kinetics of the reduction of aliphatic halides catalyzed by electrode-mounted films of didodecyldimethylammonium bromide containing myoglobin acting as a redox enzyme were investigated. The resulting products, which possess similar properties to products generated by anaerobic bacteria- and cytochrome P450-catalyzed reductions, underscored the usefulness of such protein-surfactant films in providing a biomembrane-like environment for the catalytic reduction of such organohalide pollutants.

The steric overcrowding in the perfluoro, perbromo and perchloro derivatives of ethane, cyclohexane, dodecahedrane and [60]fulleranes varies from minor to considerable. Steric overcrowding leads to the destabilization of C20X20 and C60X60 (X = H, F, Cl and Br) species. Although the steric effect induced destabilization is high in C6Br12, C20F20 and C20Cl20, its effect in C6F12 and C6Cl12 species is small but not negligible. In highly packed molecules, overcrowding is partly avoided by elongation of their C-C bonds. 1,3-diaxial repulsions dominate the steric interactions in perhalogenated cyclohexanes.

The Sb(OTeF5)6 - anion will be the most advantageous and stable weakly coordinating anion in its class according to the results of the syntheses of silver(I) salts of the weakly coordinating anions. Metathesis and subsequent recrystallization yielded diffraction-quality crystals of the dihaloalkane complexes. Crystallographic data for the dihaloalkane complexes is discussed.

Use of 2-bromo-3-methylpropanal, an alpha-bromo carbonyl compound, catalyzes the formation of (2-bromoethyl)benzene by the anti-Markovnikov addition of gaseous hydrogen bromide to styrene. Addition of 2-bromo-2-methylpropanal leads to the formation of stable 2-methylpropanal radicals and thereby promotes the free radical chain pathway generating (2-bromoethyl)benzene in high yields.

The dehalogenation of aliphatic halocarbons trichloroethylene (TCE) and CCl4 by lignin peroxidase of Phanerochaete chrysosporium was investigated. It is shown that TCE and CCl4 were mineralized by ligninolytic P. chrysosporium. In addition, other highly oxidized hydrocarbons were reductively dehalogenated during the reductive reaction. There are indications that the intermediaries in the process are not harmful to the environment.

The use of mineral-supported cobalt macrocycles as nonspecific biomimetic catalysts for the reductive dechlorination of halogenated hydrocarbons in water was investigated. Carbon tetrachloride was used as a model compound for halogenated hydrocarbons. The results showed that mineral-supported cobalt macrocycles are catalytically active in the dechlorination of carbon tetrachloride. The initial rates of reaction followed Michaelis-Menten kinetics.

Examination of the conditions necessary for selective monosubstitution of dihalides through an electrochemically induced S(RN)1 reaction reveals that use of nucleophiles, which function as electron-donating groups upon attachment with the aromatic ring, favors monosubstitution. Indirect electrolysis at low current favors the formation of monosubstituted products. Products differ for reactions induced by photochemical initiation and electrochemical initiation, and abilities of these methods to generate monosubstitution anion radical, ArNuX(.-) account for the differences.