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The process of Infrared Multiphoton Dissociation (IRMPD) was studied in a mixture of vinyl bromide/chlorodifluoromethane (VBr, C2H3Br/CF2HCl) using single and double infrared pulsed transverse excitations atmospheric CO2 laser beams. The dissociation of VBr was investigated using FTIR, and the product composition was analysed, and various dissociation routes were proposed. The study found that the VBr molecules were more heavily dissociated when exposed to the CF2HCl environment than without it. By using a time-resolved LIF, the kinetics reactions with CF2HCl were explored under pseudo-first-order conditions, and the quenching rate constant for the interaction between CF2HCl and C 2 d 3 Π g was published using the classical Stern–Volmer model. The impact of pulsed laser heating on the generation of C 2 a 3 Π u radicals was also observed. The decrease in the intensity of the C 2 (a 3 Π u) LIF signal was due to faster recombination of the C 2 a 3 Π u radicals, together with a decrease in V - V ′ energy transfer and the pressure oscillations produced by the effect of pulsed laser heating in the irradiated volume and the experimental conditions. [ABSTRACT FROM AUTHOR]

Annulation reactions of pyridine-2-sulfenyl bromide with vinyl and allyl ethers proceeded regioselectively, but with opposite regiochemistry. Reactions with vinyl ethers led to 3-organyloxy-2,3-dihydro[1,3]thiazolo[3,2-a]pyridin-4-ium bromides (91–99% yields), while allyl ethers gave 2-substituted derivatives of 2,3-dihydro[1,3]thiazolo[3,2-a]pyridin-4-ium (90–98% yields). Tricyclic condensed compounds were synthesized by reactions of pyridine-2-sulfenyl bromide with cyclic ethers (2,3-dihydrofuran, 3,4-dihydro-2H-pyran and 2,5-dihydrofuran). [ABSTRACT FROM AUTHOR]

2,3-Dibromo-2-methylpropanamides with different substituents on the nitrogen atom were synthe-sized, and their transformations by the action of potassium tert-butoxide in THF were studied. 2,3-Dibromo-N-(4-methoxyphenyl)-2-methylpropanamide and 2,3-dibromo-N-(2,5-dibromo-4-methoxyphenyl)-2-methyl-propan-amide reacted with 1–2 equiv of t-BuOK to give the corresponding N-substituted 3-bromo-3-methyl- and 3-methylideneazetidin-2-ones with acceptable yields and selectivity. Increase of the amount of t-BuOK to 3–5 equiv led to significant reduction of the yield of vinyl bromides and 3-methylideneazetidin-2-ones. On the other hand, the reaction of 2,3-dibromo-N-(tert-butyl)-2-methylpropanamide with t-BuOK afforded 3-(tert-bu-toxymethyl)-1-tert-butylazetidin-2-one with a good yield and selectivity. [ABSTRACT FROM AUTHOR]

Hexabromocyclododecanes (HBCDs) have been frequently detected in environment. The isomerization between HBCDs and thermodynamic properties of unimolecular and bimolecular decomposition reactions of (−)-α-HBCD and (−)-γ-HBCD have been investigated using the quantum chemical method. The results show that isomerization via 1,2-shift of Br atoms occurs between the (−)-α/(−)-γ, (+)-α/(+)-γ, and (+)-β/(−)-β counterparts of HBCDs. Self-decomposition of HBCDs to pentabromocyclododecenes and HBr progresses slowly at low temperature but becomes competitive with the isomerization reactions at high temperature. The generated products are also toxic pollutants to the aquatic organisms. The reaction of two commonly detected HBCDs, (−)-γ-HBCD and (−)-α-HBCD, with OH radical and H atom have been studied. (−)-γ-HBCD has bigger rate constants in the reaction with OH radical and H atom than (−)-α-HBCD all over studied temperature. After a series of unimolecular or bimolecular reactions, the formed pentabrominated intermediate can decompose into ethane, vinyl bromide, and 1,2-dibromoethylene after sufficient heat adsorption. [ABSTRACT FROM AUTHOR]

The synthesis of di-cationic surfactants were occurred by the reaction of three straight-chain amide derivatives with (2-bromoethyl)trimethylammonium bromide. After characterization of these di-cationic surfactants using FT-IR and NMR, the corrosion inhibition tests were performed at room temperature (25°C) in 1.0, 2.0 and 4.0 M of HCl solutions for different immersion times. Over 92% of corrosion inhibition efficiencies were obtained from the weight loss measurements. As evidence for the preventing of the oxidation on carbon steel, very small amount of corrosion rates were measured from the weight loss values. To establish the inhibition efficiency results in 1.0, 2.0 and 4.0 M of HCl solutions, SEM analysis of the metal coupons used were performed. [ABSTRACT FROM AUTHOR]

Synthetic procedure to access the first representatives of a new series of 3-monosubstitued functional derivatives of 1-alkoxy-1-triazene 2-oxides, i.e., 1-alkoxy-3-(2-hydroxyethyl)- and 1-alkoxy-3-(2-acetoxyethyl)-1-triazene 2-oxides, were elaborated. 1-Alkoxy-3,3-bis(2-hydroxyethyl)-1-triazene 2-oxides were used to derive 3-(2-acetoxyethyl)-, 3-(2-bromoethyl)- and 3-(2-cyanoethyl)substituted 1-alkoxy-3-(2-acetoxyethyl)-1-triazene 2-oxides. [ABSTRACT FROM AUTHOR]

Highly functionalized (E)-2-arylvinyl bromides were prepared in high yields through a new convenient access by acylation of (E)-4-(2-bromovinyl)phenol with fatty and aromatic acids at room temperature using dicyclohexyl carbodiimide (DCC) and dimethylaminopyridine (DMAP). [ABSTRACT FROM AUTHOR]

An efficient synthetic method for 11-deoxyanthracycline AB synthons is described. A versatile key intermediate vinyl bromide 3 was prepared from 5-methoxy-1-tetralone in three steps, and then was converted to the allylic alcohols 4 and 8 which, in tum, fumished highly fuctionalized AB synthons 7 and 12, respectively, via sequential epoxidation-reduction-protection processes. [ABSTRACT FROM AUTHOR]

Although formation of DNA adducts has been postulated for several halomethanes, no chemical identification of such adducts has been performed so far. There is, however, evidence that methyl chloride does not act biologically as a DNA methylating agent. 1,2-Dichloroethane and 1,2-dibromoethane are activated through conjugation with glutathione. There is some evidence for formation on an N-7 adduct of guanine which carries an ethyl-S-cysteinyl moiety. Extensive work has been published on adducts of vinyl chloride, both in vitro and in vivo. The major DNA adduct is 7-(2-oxoethyl)guanine; a minor adduct appears to be N,3-ethenoguanine. Other 'etheno' adducts, i.e., 1,N-ethenoadenine and 3,N-ethenocytosine, are readily formed with DNA, vinyl chloride, and a metabolizing system in vitro and with RNA in vivo, but are usually not detected as DNA adducts in vivo. The data on DNA alkylation by vinyl chloride (and vinyl bromide) metabolites are compared with those of structurally related compounds (acrylonitrile, vinyl acetate, vinyl carbamate). [ABSTRACT FROM AUTHOR]

An improved pharmacokinetic model is described for inhalation of volatile xenobiotics from a closed gas phase system. This model is based on steady-state kinetics and covers metabolic elimination processes of either first-order, zero-order, or Michaelis-Menten characteristics. It is emphasized that the distribution of a volatile compound between gas phase and organism under steady-state conditions may be much different from a static equilibrium obtained in absence of metabolism, as it is observed after application of a metabolic inhibitor. A re-analysis of previous experimental data on dose-dependent pharmacokinetics of different haloethylenes reveals that, in general, the metabolic elimination processes of the rapidly equilibrating mono-haloethylenes (and vinylidene fluoride) can be resolved with excellent accuracy into sections of first-order and zero-order kinetics. Other compounds show a more smooth transition from first-order elimination (at lower atmospheric concentrations) into conditions of saturation (dichloroethylenes, trichloroethylene). The analyses are consistent with a recent concept of Andersen (1980) that metabolic elimination of inhaled xenobiotics is limited by either the capacity of metabolic enzymes or factors of transport to the metabolic sites. [ABSTRACT FROM AUTHOR]

Inhalation pharmacokinetics of the halogenated ethylenes vinyl fluoride (VF), vinylidene fluoride (VF), vinyl chloride (VC1), vinylidene chloride (VC1), cis- and trans-dichloroethylene (cis-DCE and trans-DCE), trichloroethylene (Tri), perchloroethylene (Per), and vinyl bromide (VBr) have been comparatively studied in the rat. Rats were exposed in a closed inhalation system to various initial atmospheric levels of halogenated ethylenes, and the decline of atmospheric concentration was followed using gas Chromatographic analysis. From pharmacokinetic analysis of the experimental curves the following general patterns of the halogenated ethylenes were derived. Distribution of the compounds in the organism and in the gas phase is determined by physical factors. For practical purposes, a relation of the equilibrium constants with the volatilities of the compounds, expressed by the boiling points, may be used: compounds with a low boiling point are enriched in tissues much less than those of a higher boiling point, and vice versa. Compounds with high accumulation in tissues (Tri, Per) need much more time for completion of the equilibration process than more volatile compounds. Metabolic elimination of halogenated ethylenes is a saturable, dose-dependent process. If animals are exposed to atmospheric concentrations of a halogenated ethylene which exceed the 'point of saturation (Sp)', elimination is determined by a zero-order law, i.e., its rate is independent of the concentration of the compound. In contrast, below saturation normal first-order kinetics apply. If the rate of metabolic elimination is related to the concentrations of the compounds in the tissue compartment, very similar rates for first-order elimination of the different halogenated ethylenes are found. This suggests a common rate limiting factor applicable for the lower concentration range. The maximal velocities ( V) of metabolic elimination of halogenated ethylenes which are reached above the 'saturation points' depend on the chemical structures of the individual compounds. In general, with the exception of Tri, further halogen substitution inhibits metabolic conversion. Of the halogenated ethylenes, VF and Per are extremely slowly metabolized. The present report also provides the data necessary for calculation of the rates of metabolism of halogenated ethylenes in rats at a given concentration of atmospheric exposure. [ABSTRACT FROM AUTHOR]

[1,2-C]Vinyl bromide was incubated with rat liver microsomes, NADPH, and polyadenylic acid, polycytidylic acid, or RNA, respectively. Part of the adenosine moieties in RNA or in polyadenylic acid were alkylated and labelled 1,N-ethenoadenosine structures were formed. Part of the cytidine moieties were converted into 3,N-ethenocytidine. In addition, a further unidentified cytidine alkylation product was observed which was not seen in experiments using [1,2-C]vinyl chloride. When rats were exposed to [1,2-C]vinyl bromide, radioactive ethenoadenosine and ethenocytidine were present in hydrolysates of liver RNA. A further alkylation product was observed in the RNA hydrolysates which did not occur in experiments using [C]vinyl chloride. The data show that vinyl bromide metabolites alkylate nucleic acids; although in general in this respect vinyl bromide and vinyl chloride behave similarly, some differences are observed in the alkylation behaviour of both compounds. [ABSTRACT FROM AUTHOR]