Bromine, elemental analysis

Calculated from elemental analysis, one bromine per chain end. 

Resin-bound 4/7-1,3-oxazines 115 were synthetized by the stepwise condensation of an amide resin 489, an aldehyde, and an alkyne. Formation of the oxazine ring took place in the presence of the catalyst BF3-Et20 via a hetero-Diels-Alder cycloaddition of the alkyne and the acyliminium 491 arising from the condensation of the amide and the aldehyde (Scheme 92). The quantitative efficacy of the process was determined by elemental analysis of a model system bearing a bromine atom on the aldehyde moiety (R =C6H4Br(p)), which indicated a 78% conversion for the heterocyclization <2001CEJ2318, 2004JC0846>. 

Elemental Analysis. The elemental analyses are presented in Table IV. The atomic ratios H/C for all drinking water samples (nos. 1-10) were between 1.28 and 1.39. These values were comparable to humic acid derived from lake sediments. However, H/C ratios were much lower when compared to the chlorinated model humic substances (e.g., 1.04-1.08 for CFH-1 and CFH-2). Bromine was present in almost negligible quantities, whereas Cl varied between 0.3 and 2.4, and S varied between 0.9 and 2.7 in the drinking water organic matter. All fractions from drinking water showed similar elemental composition. However, they differed from the elemental composition of the CFH samples in all respects, especially in chlorine content. 

Using the bromine-lithium-boron exchange strategy, Muller and Lachmann reported in 1993 a series of MPB, DPB, and TPB 27-29 (Scheme 20) All of these compounds were isolated by crystallization and characterized by IR, multinuclear NMR (aH, 13C, 31P, and 11B), and elemental analysis. The presence of P-B interactions was spectroscopically apparent and monomeric closed structures were authenticated crys-tallographically for 27 and 28 (see Section III). 

Thus, 3-acclyl-4-hydroxychromcn-2-one (17) reacts with bromine in a conventional manner (bromine/acetic acid) to give substitution products at the aromatic nucleus as the major product [47,48]. For example, 3-acetyltropolone and 4-acetyltropolone were reacted with bromine to afford the corresponding substitution products at the tropolone nucleus as the main products [49,50]. For this reason, 17 was treated with phenyltrimethylammo-nium tribromide [51-53] (Scheme 6). The reaction was carried out at room temperature using tetrahydrofuran as the solvent. The structure of 18 was determined on the basis of spectral data and elemental analysis. 

To understand the mechanism of the lithographic process, the selectivity of the bromination reaction and the structure of the brominated product had to be determined. The results of IR spectroscopy and elemental analysis... 

End analysis by GC-MS of bromo and iodo derivatives of aromatic amines (Section III.B.4) show easily recognizable ions due to the presence of heavy atoms. A convenient alternative to GC-MS for end analysis of halogenated derivatives is by GC-ECD. The scanning mode acquisition MS of the brominated analytes show characteristic (n + 1)-multiplets with two mass unit separations for ions containing n Br atoms, stemming from the natural isotope distribution of this element. Analysis of halogenated derivatives showed that about 20 aromatic amines were present at ppb levels in industrial wastewater and ground water from a landfill and a former ammunition plant. In the latter case, most... 

A suspension of dry, PEG-free TentaGel resin 82 (see above) and quinoline toluenesulfonate (25 g, 83 mmol, 2.02 equiv.) in 1,2-dichloroethane (DCE) (1.5 L) was heated to reflux while continuously removing the solvent and traces of water. After about 500 mL of distillate had been collected, a solution of 2-bromo-l,l-diethoxyethane (50 mL, 332 mmol, 8.1 equiv.) in 1,2-dichloroethane (500 mL) was added and the mixture was maintained at reflux for 4 h with continuous removal of EtOH/DCE. Thereafter, the resin was washed with DMF (500 mL) and dioxane (500 mL) and then lyophilized to give the desired product 83 (98 g). The loading level was determined by quantification of bromine by elemental analysis (approximately 0.31 mmol g ). 

Elemental analysis also proved to be a helpful routine method for determining reaction progress and calculate resin loading, especially when bromine or fluorine tags are present. 

Kemp, K. and Danscher, G. (1979). Multi-element analysis of the rat hippocampus by proton induced X-ray emission spectroscopy (phospurus, sulphur, chlorine, potassium, calcium, iron, zinc, copper, lead, bromine and rubidium). Histochemistry, 59, 167... 

Analysis of Reagent Purity H NMR, IR, elemental analysis. Preparative Methods the title reagent is prepared by the reaction of 2-(methylsulfonyl)-3-phenyl-2-propenyl alcohol and phosgene (eq 1). The alcohol is obtained from the corresponding allylic bromide by formate-catalyzed hydrolysis. The synthesis of the bromide involves the Cu(OAc)2-catalyzed addition of methanesulfonyl chloride to -methylstyrene followed by elimination of hydrogen chloride and subsequent free radical bromination of the methyl group (eq 1). ... 

Ruiz et al. [39] synthesized a series of l,4-bis(2-thienyl)-2,5-disubstituted benzene monomers with long-chain substituents at the 1- and 4-positions of the benzene ring by reacting the disubstituted benzene with bromine to provide reactive sites at the 2- and 5-positions for coupling with 2-thienyl zinc chloride in the presence of palladium tetrakis (triphenylphosphine) as catalyst at 50°C. In addition, they characterized the monomers using FT-IR, IH NMR, 13C NMR and elemental analysis. 

Neoh and co-workers [110] investigated the simultaneous chemical copolymerization and oxidation of pyrrole and A-methylpyrrole by bromine and iodine. By varying the monomer feed ratio, they could in effect control the copolymer composition. Based on elemental analysis of the copolymers, they determined that ri = 1.13 and r2 = 0.35 for pyrrole and 1-methylpyrrole, respectively. In the copolymerization induced by bromine, the electrical conductivity, thermal stability and Br content of the doped copolymer decreased with increasing concentration of A/-methylpyrrole in the copolymer. When iodine was included in the charge, the halogen content of the copolymers did not vary substantially, but the electrical conductivity and thermal stability of the doped copolymer also decreased with an increase in the fraction of A/-methylpyrrole in the copolymer. 

A and B are isomeric bromoconduritols as shown by elemental analysis and NMR spectra of their acetylation products. Both have the bromine substituent in an allylic position. Relative rates of dehydrobromination with sodium ethylate lead to the following tentative assignments A (3,5/4,6)- and B (3,5,6/4)-6-bromo-3,4,5-trihydroxycyclohex-l-ene. 

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