Showing papers on "Bromide published in 1984"

Dimethylboron bromide and diphenylboron bromide: cleavage of acetals and ketals

Abstract: Reactivite des boranes du titre vis-a-vis du clivage d'acetals cycliques et acycliques, de cetals, de perhydropyrannyl- et perhydrofuryl ethers, de glycosides de methyle, d'acetonides, d'ethers de -methoxymethyle, -methoxyethoxymethyl et methylthiomethyle

New aspects of the behaviour of alkyltrimethylammonium bromide micelles : light scattering and viscosimetric studies

Abstract: Etude du comportement des micelles de bromure d'alkyltrimethylammonium avec alkyl=lauryl-, myristyl- et palmityl-, dans un domaine de concentrations entre la concentration crique micellaire et 0,42 M

Tris(bipyridyl)ruthenium(II)-photosensitized reaction of 1-benzyl-1,4-dihydronicotinamide with benzyl bromide

Abstract: An NADH model compound, 1-benzyl-1,4-dihydronicotinamide (BNAH), reduces benzyl bromide to yield toluene as the main product under irradiation of the absorption band of BNAH in the presence of pyridine in acetonitrile, while the addition of a sensitizer tris(bipyridyl)ruthenium(II){[Ru(bpy)3]2+} to the BNAH-benzyl bromide system results in a drastic change in the photoreduced products, yielding 1,2-diphenylethane as the main product. Photosensitization by [Ru(bpy)3]2+ has been shown to change the mechanism of the photochemical reaction of BNAH with benzyl bromide; reaction in the absence of [Ru(bpy)3]2+ proceeds by a radical chain mechanism involving benzyl bromide. However, the [Ru(bpy)3]2+-mediated photoreduction of benzyl bromide with BNAH occurs in the presence of [Ru(bpy)3]2+, where benzyl bromide is subject to two-electron reduction by [Ru(bpy)3]+ which is formed by an electron transfer from BNAH to the excited state of [Ru(bpy)3]2+.

Anion-exchange chromatographic determination of bromide in serum.

Abstract: In this liquid-chromatographic method for the determination of bromide in human serum, an important and unique feature is pre-analysis ultrafiltration of the sample, which effectively removes proteins. The chromatographic system consists of an anion-exchange column (Whatman Partisil SAX 10-micron particles), an isocratic phosphate-buffered mobile phase, and ultraviolet detection at 195 nm. The absolute detection limit, 0.6 ng of bromide, makes this method the most sensitive assay for serum bromide yet reported. The day-to-day CV ranged from 1.6% to 4.9%. Analytical recovery of bromide added to serum samples ranged from 96.2% to 108.8%. Data on bromide in serum are presented for adults and newborns and for adults given bromide orally.

Kinetics and products of the reactions of ozone with various forms of chlorine and bromine in water

Abstract: Ozone reacts with various halogen compounds (chlorine, chloramines , bromine , and bromide) which may be present in water. Chlorine produces Cl− and ClO− 3; chloramines produce NO− 3 and Cl−. Bromide produces bromine , which acts as a secondary disinfectant, but can generate haloforms and interfere in O3 determinations. Brominepartly regenerates Br causing a catalytic destruction of O3. The kinetics of these reactions are described and interpreted with respect to their importance in water treatment.

Hydrophobic Vitamin B12. III. Incorporation of Hydrophobic Vitamin B12 Derivatives into Single-Compartment Vesicles and Their Alkylation in Various Molecular Aggregates

Abstract: The incorporation of hydrophobic vitamin B12 derivatives into the single-compartment vesicles of N,N-didodecyl-Nα-[6-(tyimethylammonio)hexanoyl]-L-alaninamide bromide (N+C5Ala2C12) was found to be primarily concerned with the extent of insolubility of the cobalt complexes in the aqueous bulk phase, while such incorporation into the single-walled vesicles of N,N-ditetradecyl-Nα-[6-(trimethylammonio)hexanoyl]-L-histidinamide bromide (N+C5His2C14) was enhanced by the coordination interaction between the cobalt complex and the imidazolyl group of the lipid. In molecular aggregates formed with hexadecyltrimethylammonium bromide, α-[4-(1,1,3,3-tetramethylbutyl)phenyl]-ω-hydroxypoly(oxyethylene), or N+C5Ala2C12, the alkylation rates of a hydrophobic vitamin B12 with 1-bromo-2-methylpropane and methyl 2-methyl-3-bromopropanoate were much enhanced relative to those in methanol. In the N+C5Ala2C12 vesicle, a two-step mechanism was observed for the alkylation with the latter reagent. The possible origin of such rate...

Synthesis and characterisation of 1,7-dimethyl-1,4,7,10-tetra-azacyclododecane: crystal structure of the nickel(II) bromide monohydrate complex of this macrocycle; thermodynamic studies of protonation and metal complex formation

Abstract: The synthesis and characterisation of the macrocycle 1,7-dimethyl-1,4,7,10-tetra-azacyclododecane (L1) are reported. The basicity constants of L1 and the stability constant of the complex [CuL1]2+ have been determined by potentiometry at 25 °C in 0.5 mol dm–3 KNO3. The macrocycle L1 behaves as a diprotic base in the pH range investigated; pD–13C n.m.r. studies indicate that only the two secondary nitrogens are involved in the protonation process. Copper(II) and nickel(II) complexes with L1 have been prepared and studied spectrophotometrically both in aqueous solution and in the solid state. The reflectance spectrum of dry yellow NiL1(ClO4)2 shows that a square-planar geometry, with the nickel(II) in the low-spin state, is achievable also with this partially methylated twelve-macrocycle. The molecular structure of the complex [NiBr(H2O)L1]Br has been determined by single-crystal X-ray analysis. The compound crystallises in an orthorhombic unit cell (space group P212121) with lattice constants a= 13.478(5), b= 11.186(4), and c= 10.585(4)A for Z= 4. Least-squares refinement converged at R= 0.046 for 910 observed reflections. The complex shows a cis-octahedral geometry, with the macrocycle co-ordinated in a folded configuration to four sites around the central nickel atom. The chirality of each nitrogen atom of the macrocycle is the same. The bromide ion and the oxygen atom of the water molecule are cis to each other. The chelate rings are all asymmetric.

Inhibition of DNA-ethidium bromide intercalation due to free radical attack upon DNA. II. Copper(II)-catalysed DNA damage by O.2-.

Abstract: The fluorescent intercalation complex of ethidium bromide with DNA was used as a probe to demonstrate damage in the base-pair region of DNA, due to the action of superoxide radicals. The O.2- radical itself, generated by gamma-radiolysis of oxygenated aqueous Na-formate solutions, is rather ineffective with respect to impairment of DNA. Copper(II) ions, known to interact with DNA by coordinate binding at purines, enhance the damaging effect of O.2-. Addition of H2O2 to the DNA/Cu(II) system gives rise to further enhancement, so that DNA impairment by O.2- becomes comparable to that initiated by .OH radicals. These results suggest that the modified, Cu(II)-catalysed, Haber-Weiss process transforms O.2- into .OH radicals directly at the target molecule, DNA-Cu2+ + O.2-----DNA-Cu+ + O2 DNA-Cu+ + H2O2----DNA...OH + Cu2+ + OH- in a "site-specific" mechanism as proposed for other systems (Samuni et al. 1981; Aronovitch et al. 1984). Slow DNA decomposition also occurs without gamma-irradiation by autocatalysis of DNA/Cu(II)/H2O2 systems. In this context we observed that Cu(II) in the DNA-Cu2+ complex (unlike free Cu2+) is capable of oxidizing Fe(II) to Fe(III), thus the redox potential of the Cu2+/Cu+ couple appears to be higher than that of the Fe3+/Fe2+ couple when the ions are complexed with DNA. Metal-catalysed DNA damage by O.2- also occurs with Fe(III), but not with Ag(I) or Cd(II) ions. It was also observed that Cu(II) ions (but neither Ag(I) nor Cd(II] efficiently quench the fluorescence of the intercalation complex of ethidium bromide with DNA.

1H NMR Studies on the Dynamics of Planar [C(NH2)3]+ Cations in the Crystal of Various Guanidinium Salts

Abstract: The temperature dependences of 1H NMR spin-lattice relaxation times and 1H NMR second moments were observed for guanidinium chloride, bromide, iodide, thiocyanate, nitrate, and perchlorate. The results of the NMR experiments carried out with the crystals of these compounds except the last one can be interpreted in terms of the C3 reorientation of the cation about its symmetry axis. The solid-solid phase transition at 454 K reported for guanidinium perchlorate could be resolved into two phase transitions taking place successively at 450 and 452 K. In the low temperature phase of this salt, the C3 reorientation of the cation is activated. The occurrence of cationic self-diffusion in the high temperature phase was confirmed by the measurements of 1H NMR relaxation times. The NMR motional parameters are evaluated for these cationic motions in the present salts. The phase transition temperature of guanidinium iodide was strongly depended on the grain size of the sample employed. Guanidinium bromide yielded a single 81Br NQR line at room temperature indicating that all bromide ions in the crystal are crystallographically equivalent in agreement with the results of X-ray analysis.

Deoxygenation of sulfoxides with boron bromide reagents

Abstract: Desoxygenation par les (bromodimethyl)-tribromo-boranes et bromo-9 bora-9 bicyclo [3.3.1] nonane, des dibutyl-, di-sec-butyl-, dibenzyl-, diphenyl- et [methyl phenyl], [benzyl methyl] sulfoxydes

Cycloadditions of trifluoroacetonitrile oxide with olefins and acetylenes

Abstract: The regio- and stereoselectivity of the cydoadditions of trifluoroacetonitrile oxide (1) with olefins and acetylenes were described. The oxide 1, generated in situ from trifluoroacetohydroximoyl bromide etherate in the presence of triethylamine, reacted with various monosubstituted olefins and acetylenes to give exclusively 5-substituted 3-trifluoromethyl-2-isoxazolines and -isoxazoles, respectively, whereas 1 cyclized with 1,2-disubstituted olefins and acetylenes to result in the formation of a mixture of two regioisomeric products. On the other hand, the cycloaddition of 1 with (Z)-β-methylstyrene afforded a mixture consisting of two regioisomeric isoxazolines retaining Z-configuration and one diastereoisomeric isoxazoline.

Double layer simulation studies in ultrahigh vacuum of anion and cation hydration at metal surfaces

Abstract: Using low energy electron diffraction (LEED), thermal desorption spectroscopy (TDS) and measurements of work function changes (Δo), the coadsorption of water and ions on metal surfaces has been studied in ultrahigh vacuum. As an example of anion specific adsorption, the hydration of bromide on Cu(110) has been characterized with regards to inner layer composition, surface hydration number and the formation of long-range order. Simulation of non-specific adsorption of lithium ions has also been attempted. On Ag(110), a drastic reduction of the binding energy of lithium in the presence of water is attributed to this type of surface hydration. Such evidence is not observed on Cu(111), where substantial fragmentation of the water seems to occur. The electrochemical relevance of these results is discussed.

Binding of 1-Decylpyridinium Bromide to Poly(vinyl sulfate)

Abstract: Binding of 1-decylpyridinium bromide onto poly(vinyl sulfate) in aqueous solution is measured by using a potentiometric titration method which employs propionyl-α-cyclodextrin as a neutral carrier in a 1-decylpyridinium selective electrode. Binding is highly cooperative and biphasic. The first step binding is reduced, while the second one increased on increasing added NaBr concentration. Temperaure dependence is very small giving an enthalpy of binding equal to −1.4 kJ mol−1.

Chlorine utilization during trihalomethane formation in the presence of ammonia and bromide

Abstract: The chlorination of humic substances in the presence of ammonia and bromide and the resultant formation of trihalomethanes (THM) are described. The presence of ammonia substantially reduced but did not eliminate THM production during the chlorination of waters containing humic substances. The presence of bromide ion in waters containing humic substances leads to increased THM formation, both in the presence and in the absence of ammonia. In waters containing ammonia, bromide, and humic substances, brominated haloforms can form upon chlorination. Brominated species comprise a larger portion of the total THMs at higher chlorine doses within the free chlorine region of the breakpoint curve than at lower dose in the subbreakpoint region. Although the THM formation reaction is slow and may not be complete even after 1 week of reaction time, the initial rate of formation is competitive with the relatively rapid reactions of bromide oxidation and chloramine formation. After free chlorine is converted to chloramines, THM production should theoretically cease. THMs will form in parallel with chloramine formation. This behavior has important implications for water utilities that use a raw water source containing low but significant levels of ammonia such as the Biscayne Aquifer, or are considering chloramine disinfection asmore » a THM control strategy.« less

Graphite intercalation compounds

Abstract: An electrically conductive composition is disclosed which comprises a graphite intercalation compound of graphite, a Bronsted acid such as hydrogen fluoride, chloride, or bromide, nitric, nitrous, sulfuric or perchloric acid, and a metal halide selected from boron trihalide, a pentahalide of a metal from Group V of the Periodic Table, a tetrahalide of a metal from Group IV of the Periodic Table and mixtures thereof.

Adiabatic compressibility of surfactant micelles in aqueous solution

Abstract: The compressibilities of micellar solutions of the surfactants sodium dodecyl sulphate (SDS), sodium decyl sulphate (SDeS), sodium octyl sulphate (SOS), sodium decyl sulphonate (SDeSon), decyltrimethylammonium bromide (DeTABr), decylammonium bromide (DeABr) and dodecyltrimethylammonium bromide (DTABr) have been determined from sound-velocity measurements. A theoretical treatment has been introduced which enables the micellar compressibility (Kmic) to be evaluated from these data. From a systematic study of the above compounds it was found that a significant factor which controls the overall compressibility of the micellar aggregate is the nature of the surfactant head group. The overall picture is that the micelle resembles an aggregate with a compressible core surrounded by a less compressible surface structure.

Deoxy‐nitrosugars. 9th communication. Chain elongation of 1‐C ‐nitroglycosyl halides by substitution with some weakly basic carbanions

Abstract: The 1-C-nitroglycosyl chloride reacted with the anions form 2-nitropropane, nitromethane, and diethyl malonate, to give the chain-extended products 2 (81%), 5 (72%), and 6 (83%), respectively. Treatment of the 1-C -nitroglycosyl bromide 7 by the lithium salt obtained form 8 gave the dodecodiulose derivative 9 (76%). Th β-D-configuration of 2 and 9 was inferred form their NMR and CD spectra. Treatment of 2 and 9 with sodium sulfide gave the enol ethers 3 (96%) and 10 (92%), respectively. The (Z)-configuration of 10 was deduced form the configuration of its hydrogenation product 11.