Coordination complexes of 2‐thienyl‐ and 2‐furyl‐mercurials

The reactions of di(2‐thienyl)mercury, 2‐thienylmercury chloride and 2‐furylmercury chloride with a variety of nitrogen‐ and phosphorus‐containing ligands have been studied. The presence of the electron‐withdrawing heteroatoms results in these mercurials being stronger acceptors than the corresponding phenylmercury compounds. The complexes have been characterized by elemental analysis, melting points, infrared, and ¹⁹⁹Hg NMR spectroscopy. 2,9‐Dimethyl‐ and 3,4,7,8‐tetramethyl‐phenanthroline form 1:1 chelate complexes, as does 1,2‐bis(diphenylphosphino)ethane, whereas ethylenediamine and 2,2′‐bipyridyl do not form complexes. Though non‐chelating ligands such as 2,4′‐ and 4,4′‐bipyridyl do not form complexes, bis(diphenylphosphino)methane forms 1:2 complexes in which the ligand bridges two mercury atoms. Monodentate ligands, such as triphenylphosphine, cause disproportionation of the organomercury chloride. 2‐Thienylmercury chloride forms a 4:1 complex with 4,4′‐dipyridyl disulfide in which it is believed that a molecule of the organomercurial is coordinated to both of the nitrogen and both of the sulfur atoms. Copyright © 2004 John Wiley & Sons, Ltd.     

Reagents with a Crystalline Coat

Tetrakis(dimethoxyphenyl)adamantane (TDA) readily forms crystalline inclusion complexes with reactive, toxic, or malodorous reagents, such as benzoyl chloride, acetyl chloride, cyclohexyl isocyanide, phosphorus trichloride, and trimethylsilyl chloride. The crystals are stable and largely free of the problematic properties of the free reagents. When exposed to solvents such as DMSO or MeOH, the reagents react, and a large portion of the TDA precipitates. The TDA‐coated reagents may lead to a safer way of storing, handling, and delivering reagents, and ultimately to synthetic protocols that do not require fume hoods.     

Determination of Arsenic in Traditional Chinese Medicine using Microwave Digestion with Flow Injection Analysis Inductively Coupled Plasma Mass Spectrometry

Arsenic present in Traditional Chinese Medicine (TCM) such as uncoated tablets, sugar coated tablet,black pills, capsules/powder, syrup, etc. was determined by using microwave digestion followed by Flow Injection Analysis (FIA) Inductively Coupled Plasma/Mass Spectrometry (ICP/MS). The effect of chloride in the determination of arsenic using FIA ICP/MS was investigated and was found that low level of chloride present do not enhance the ⁷⁵As signal significantly.     

Explanation for the apparent absence of collapse of polyelectrolyte brushes in the presence of bulky ions

The conformational behavior of poly[2-(methacryloyloxy)ethyltrimethylammonium chloride] (PMETAC) brushes with different chain density in the presence of large benzyltributylammonium chloride (BTBAC) ions has been studied by a Quartz Crystal Microbalance with Dissipation (QCM-D) and Scanning Force Microscopy. Dense brushes do not collapse in the presence of BTBAC solutions of increasing ionic strength, contrary to what is observed in the presence of NaCl. Brush collapse can be observed for low-ionic-strength solutions of BTBAC when the brush density has been reduced. These phenomena can be explained by considering the Hofmeister series as well as ion size and free space in the brush.     

Neutron activation analysis of arsenic in rocks and sediments by direct evolution with chloride- and bromide-condensed phosphoric acid reagents

A simple method is presented for the determination of arsenic in rocks and in sediments by neutron activation. After irradiating a sample it is, without any other treatment, directly heated in condensed phosphoric acid containing sodium chloride or sodium bromide to evolve arsenic as arsenic(III) chloride or bromide. The distillate is absorbed in distilled water, in which arsenic is later precipitated in elementary form by adding hypophosphite to the solution. From arsenite, arsenic(III) oxide, arsenate and arsenic(III) sulphide, arsenic chloride can be evolved with NaCl-CPA reagent, but elementary arsenic and arsenic(V) oxide do not react with it. However, metallic arsenic is found to react with KIO₃-NaCl-CPA and arsenic(V) oxide with the NaBr-CPA, both both evolving arsenic(III) chloride or bromide. Therefore, successive distillations, the first with NaCl-CPA and the second with NaBr-CPA, give a satisfactory means of differential determination of arsenic(III) and arsenate as well as arsenic(V) oxide. For the elementary arsenic a problem still now remains. The chemical recovery of carrier goes well beyond 95%. Part of this work was performed at the Research Reactor Institute, Kyoto University.     

Breakdown of organic mercury compounds by hydrochloric acid—permanganate or bromine monochloride solution for the determination of mercury by cold-vapour atomic absorption spectrometry

Hydrochloric acid—potassium permanganate and bromine monochloride are examined for the decomposition of methylmercury(II) chloride, Ceresan, phenylmercury(II) borate and thiomersal added to waters. Both procedures give quantitative recovery of mercury. Bromine monochloride has many advantages: blanks are low, the limit of detection (3σ) is 0.06 μg Hg l^?1, routine work is simplified because only two reagents are needed and the reaction time is 5–10 min. The reagent also acts as a preservative. Common contaminants (chloride, bromide, sulphide, alcohols, benzene) do not interfere.     

Synthesis and binding activity of 4-azanicotine

4-Azanicotine ( 1 ) has been synthesized by the cyclopropylimine rearrangement. A study of several Lewis acids as possible catalysts for the NMF-mediated cyclopropyl imine rearrangement of cyclopropyl-2-pyrazinylmethanone ( 4 ) indicated that both aluminum chloride and magnesium chloride are suitable catalysts, lithium bromide shows only a trace of activity and zinc chloride, titanium tetrachloride, and titanium tetra-isopropoxide show no activity. Compound 1 , in which the aromatic ring is less basic than in nicotine, and 6-aminonicotine ( 5 ), in which the aromatic ring is more basic, have been compared with the binding properties of nicotine in the P2 rat brain preparation. Compound 1 binds with an affinity very similar to that of nicotine at two of the receptor sites, 5 binds at these sites but with a lower affinity. Unlike nicotine, 1 and 5 do not bind at the very high affinity ‘upregulatory’ site.     

Alkylation of furan catalysed by arenetricarbonylmolybdenum

Furan reacted with t-butyl chloride at 130°C in the presence of ArMo(CO)₃ to yield 2-t-butylfuran and 2,5-di-t-butylfuran. The catalyst was largely deactivated after 12 h. Up to 150 alkylation events occurred per Mo atom. At low conversions (<10%), using a furan/Mo ratio of 1000/1, the yields of 2-t-butylfuran were high (typically 65–80%). Yields fell sharply with increasing catalyst concentration. Butylation of 2-t-butylfuran occurred more readily than that of furan, and 2,5-di-t-butylfuran was formed in high yield at 30% conversion. Both furan and 2-t-butylfuran reacted with t-butyl chloride more than 50 times as fast as toluene. Evidence is given that the catalytic species do not contain chloride.     

Kinetics of the Zn(II)/Zn(Hg) electrode reactions in DMSO solutions of halide ions

The electrode reaction Zn(II)/Zn(Hg) in complex chloride, bromide, and iodide solutions with DMSO as solvent and ammonium perchlorate as supporting electrolyte has been studied at the equilibrium potential by the faradaic impedance method and a square-wave method. Furthermore, double-layer data have been determined by electrocapillary measurements. The results indicate that the zinc chloride and bromide complexes do not contribute noticeably to the exchange current density, while in the iodide system both the solvated zinc ion and the first complex take part in the charge transfer. From the dissimilar results valid for water and DMSO solutions the conclusion is made that probably ligand bridging at the amalgam by the halide ions is operative in water solutions, whereas in DMSO the larger solvent molecules adsorbed can form a steric hindrance to ligand bridging by chloride or bromide ions.     

Liquid polymer nano-PEBBLEs for Cl- analysis and biological applications

The first nanometer scale anion sensing fluorescent spherical nanosensors, or PEBBLEs (probes encapsulated by biologically localized embedding) have been developed for the intracellular monitoring of chloride. The general scheme for the polymerization and introduction of sensing components creates a matrix that allows for the utilization of the highly selective ionophores used in poly(vinyl chloride) and poly(decyl methacrylate) ion-selective electrodes. We have demonstrated that our previously developed scheme for cation sensors can be utilized to tailoring selective submicron sensors for use in intracellular measurements of biologically relevant anions for which selective enough fluorescent probes do not exist. Three schemes were attempted for the development of chloride sensitive PEBBLEs. The first two used the Chloride ionophore indium(III) octaethylporphyrin chloride (In(OEP)Cl) (1) as an ionophore working in tandem with a chromoionophore and (2) as a chromoionophore with a peak shift generated by chloride mediated breaking of hydroxide ion-bridged porphyrin dimer. The third method used the optically silent Chloride ionophore III (ETH 9033) working in tandem with chromoionophore III (ETH 5350) to indirectly monitor Cl- activity by reporting the H+ coextracted into the matrix. Method 3 gave the most promising results, at a pH of 7.2 these PEBBLEs have a limit of detection of 0.2 mM Cl- with a linear dynamic range of 0.4 mM-190 mM Cl-. These PEBBLEs were delivered into C6 glioma cells, utilizing a gene gun, and intracellular chloride levels were monitored during ion-channel stimulation by kainic acid.     

A new method for the direct precipitation of aluminium in the presence of iron

It is shown that aluminium can be precipitated as benzoate from solutions containing up to 1 gram of iron in the presence of thioglycollic acid, which reduces the iron and forms a soluble complex with ferrous iron. Very large amounts of such salts as ammonium chloride, sulphate and perchlorate, and sodium chloride do not interfere, nor do other divalent metals. Molybdates and tungstates are without effect, but chromium, vanadium and titanium interfere. This limits the direct application of the method in metallurgical analysis, but in many cases this speedy and complete separation will have many uses.     

Degradation of vinylidene chloride/phenylacetylene (VDC/PA) copolymers. Effect of internal unsaturation on poly(vinylidene chloride) stability

The thermal degradation of vinylidene chloride/phenylacetylene copolymers containing small but varying amounts of phenylacetylene has been examined in both the solid phase and in bibenzyl solution. Incorporation of phenylacetylene into the poly(vinylidene chloride) structure greatly facilitates degradative dehydrochlorination. Indeed, the presence of phenylacetylene promotes the formation of polyene segments during the polymerization process so that all the copolymers, even at very low phenylacetylene loading, are tan in color. The decreased stability of polymers containing interal unsaturation arises from an increased rate of initiation for degradative dehydrochlorination. The propagation rate is largely unaffected by the level of unsaturation initially present in the polymer. The ratio of hydrogen chloride to stilbene formed for degradation of these copolymers in bibenzyl solution is approximately 35:1. This suggests that the chlorine atom of the initially-formed radical pair preferentially abstracts an adjacent hydrogen atom rather than interacting with solvent, i.e., the chain-carrying radical pair does not dissociate appreciably as the unzipping dehydrochlorination occurs. Thus random double bonds introduced in a variety of ways may be identified as principal defect sites responsible for the initiation of the degradative dehydrochlorination of poly(vinylidene chloride). Species which promote the degradation of poly(vinylidene chloride) probably do so by facilitating the introduction of random double bonds into the structure.     

The Estimation of Total Non-Volatile Nitrosamines and Nitrosamides in Microgram Amounts

Abstract

Nitrosamines and nitrosamides are denitrosated by thionyl chloride to form nitrosyl chloride, which can be volatilized in a stream of nitrogen, trapped in alkali and determined as inorganic nitrite. Other compounds containing a N-O bond such as nitramines and nitramides do not react similarly under the conditions used.     

The determination of chloride by microwave helium plasma emission spectrometry using a hydrogen chloride generation technique

Hydrogen chloride is generated from aqueous solution from a concentrated sulphuric acid—potassium sulphate mixture and is passed into a microwave-induced atmospheric pressure helium plasma. Measurement at the Cl-(II) 479.5-nm line gives a linear calibration graph over the range 6 ng (detection limit) to 50 μg of chloride. Other halides, and arsenic, do not interfere, but Te and Hg depress the emission.     

Structural characterization of zinc(II) chloride in aqueous solution and in the protic ionic liquid ethyl ammonium nitrate by x-ray absorption spectroscopy

Extended x-ray absorption fine structure (EXAFS) spectroscopy has been used to investigate the species and structures existing in a series of ZnCl(2)-H(2)O-NaCl solutions with different chloride/zinc ratios and in a solution of ZnCl(2) in the protic ionic liquid ethyl ammonium nitrate (EAN). The average coordination numbers and distances of zinc species were determined from the analysis of the EXAFS data. In aqueous solution the number of chloride ions tightly bounded to Zn(2+) is significantly related to the chloride/zinc ratio, and no inner complex formation between Zn(2+) and Cl(-) ions has been detected for low ZnCl(2) concentration (0.1 and 0.2 M). Conversely, in the same concentration range (0.13 M) the ZnCl(2) species do not dissociate in EAN and the Zn(2+) first coordination shell has two chloride ions and is completed by two oxygen atoms of the nitrate anion. The results of this investigation show that notwithstanding the existence of similar characteristics between EAN and water, the solvation properties of the two solvents are markedly different.     

Oxidimetric determination of thiourea, thiosulphate and sulphite with thallic perchlorate in acid medium

Conditions have been established for the titrimetric estimation of thiourea, thiosulphate and sulphite with thallic perchlorate, with visual end-points, in perchloric and sulphuric acid medium. In the direct determination, chloride and bromide interfere. In the indirect iodometric determination. Cu(2+) and Fe(2+) interfere, but chloride and bromide do not.     

Preparation of 6-styrylphenanthridines

(6-Phenanthridinylmethyl)magnesium halides do not react with aromatic and aliphatic aromatic ketones but do react with aromatic aldehydes to give the corresponding carbinols. The latter are readily dehydrated to the corresponding 6-styrylphenanthridines. 6-Cyanomethylphenanthridine reacts with aromatic aldehydes in the presence of sodium ethoxide to give 6-(α-cyanostyryl)phenanthridines and is converted to 5-acyl-6-cyanomethylene-5,6-dihydrophenanthridine on heating with acetic anhydride or benzoyl chloride.     

Real energies of ferricinium cation transfer from water to organo-aqueous solvents

The redox potentials of ferrocene-ferricinium couple are determined for five organo-aqueous systems with respect to a reversible chloride electrode in the same solvent. Combined with the literature data on real (and some chemical) transfer energies of chloride ion, the effective real energies of ferricinium transfer from water into organo-aqueous mixtures are determined. These values do not obey the Born equation. Most probably, this is due to the selective solvation of cation by water and of neutral ferrocene molecule by an organic component.     

Novel gallium(III) phthalocyanine derivatives – Synthesis,photophysics and photochemistry

The syntheses of gallium(III) chloride phthalocyanine {(Cl)GaPc}, octaphenoxyphthalocyaninato gallium(III) chloride {(Cl)GaOPPc} and octakis(4-tert-butylphenoxy)phthalocyaninato gallium(III) chloride {(Cl)GaOTBPPc}; as well as their photophysical and photochemical parameters are hereby presented. Fluorescence quantum yields do not vary much among the three metallophthalocyanines (MPcs); therefore it was concluded that the effect of the substituents is not significant amongst (Cl)GaPc, (Cl)GaOPPc and (Cl)GaOTBPPc. Solvents effects, however, had an effect on the results. Triplet quantum yields were found to be lower in DMSO than in DMF and toluene. The rate constants for fluorescence, intersystem crossing and internal conversion as well as fluorescence and triplet lifetimes are reported. We have also reported photodegradation and singlet oxygen quantum yields. There was no clear correlation between the later parameters. It was, however, established that the three MPcs were stable.     

Plasticized PVC reinforced with cellulose whiskers. I. Linear viscoelastic behavior analyzed through the quasi‐point defect theory

In a previous article, the processing of nanocomposite materials of plasticized poly(vinyl chloride) (pPVC) reinforced by cellulose crystalline whiskers was presented as well as preliminary dynamic mechanical measurements. The purpose of the present work is to evaluate the possible change of molecular dynamic of poly(vinyl chloride (PVC) at the interface with cellulose whiskers. The analysis, based on the quasi‐point defect (qpd) theory for the anelastic deformation of amorphous polymer, confirms that PVC is heterogeneous. Thus, the matrix is described as a parallel assembly of phases with different plasticizer concentration (i.e., different glass transition temperature). It is shown that the whiskers do not lead to supplementary relaxation in the matrix, at least in the time–temperature window of the study, but, the satisfying modeling of the composite supports the assumption of a thin layer of immobilized phase around the whiskers. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2151–2164, 1999