Isotope bromine

Watkins and Pound (104) performed an experiment which illustrates the effect of strain on the magnetic resonance of bromine and iodine nuclei in cubic KBr and KI. These crystals were subjected to plastic deformation (a 22% change in dimension occurred along the 100 axis for the KI crystal) and it was found that the intensity of the resonance line in the original undeformed crystals decreased to 0.4 of its original value for the bromine isotopes (Br , Br , I = and to 0.3 of its original value for the I (I = resonance. 

The presence of a chlorine or bromine atom results in an intense (M + 2) peak due to the presence of either two chlorine isotopes (chlorine-35 and chlorine-37) or two bromine isotopes (bromine-79 and bromine-81). In the case of chlorine, the (M + 2) peak is about one-third the intensity of the M ... 

The element bromine, Br (atomic number 35), has two major isotopes of similar abundance, both around 50 percent. The atomic mass of bromine is reported in the periodic table as 79.904 atomic mass units. Choose the most likely set of mass numbers for these two bromine isotopes (a) 80Br, 81 Br (b) 79Br, 80Br (c) 79Br, 81 Br. 

M. Li and J. A. Kinzer, Structural analysis of oligosaccharides by a combination of electrospray mass spectrometry and bromine isotope tagging of reducing-end sugars with 2-amino-5-bromopyridine, Rapid Commun. Mass Spectrom., 17 (2003) 1462-1466. 

B. Physical and Radiochemical Studies with Bromine Isotopes. 470... 

C. Chemical Syntheses of Organic Compounds Labelled with Bromine Isotopes... 

Experiments on the bromination of equilibrated ketone-acetal systems in methanol were also recently performed for substituted acetophenones (El-Alaoui, 1979 Toullec and El-Alaoui, 1979). Lyonium catalytic constants fit (57), but for most of the substituents the (fcA)m term is negligible and cannot be obtained with accuracy. However, the relative partial rates for the bromination of equilibrated ketone-acetal systems can be estimated. For a given water concentration, it was observed that the enol path is more important for 3-nitroacetophenone than for 4-methoxyacetophenone. In fact, the smaller the proportion of free ketone at equilibrium, the more the enol path is followed. From these results, it can be seen that the enol-ether path is predominant even if the acetal form is of minor importance. The proportions of the two competing routes must only depend on (i) the relative stabilities of the hydroxy-and alkyoxycarbenium ions, (ii) the relative reactivities of these two ions yielding enol and enol ether, respectively, and (iii) the ratio of alcohol and water concentrations which determines the relative concentrations of the ions at equilibrium. Since acetal formation is a dead-end in the mechanism, the amount of acetal has no bearing on the relative rates. Bromination, isotope exchange or another reaction can occur via the enol ether even in secondary and tertiary alcohols, i.e. when the acetal is not stable at all because of steric hindrance. 

Short-lived bromine Isotopes in fission products, 15.5-... 

It should be noted that the CHj group and the nitrogen-bound carbon atom of the carbazole moiety ue subject to the same effect, arising from the dipolar coupling to the quadrupolar N nucleus. In this case, however, since the quadrupole coupling constant is much smaller than for the bromine isotopes (2.16 MHz for N-methyl pyrrole (29)) the interaction is much weaker and manifests itself only as a moderate broadening of the peaks with some ill-resolved structure. For these asymmetric resonances, the chemical shifts were measured at the center of gravity. 

Cuyckens, F. et al., Use of the bromine isotope ratio in HPLC-ICP-MS and HPLC-ESI-MS analysis of a new drug in development, Anal. Bioanal. Chem., 390(7), 1717, 2008. 

The first reports of Zeeman-perturbed bromine NQR, both using single crystals of NaBrQa, confirmed prior measurements of the Br magnetic dipole moment ° and also highlighted the fact that Kriiger s ° Zeeman-perturbed NQR theory was valid for both bromine isotopes. ... 

We did not observe an isotope-dependent chemical shift under our experimental conditions, if a shift is measured for one of the bromine isotopes, it will be the same, within experimental error, for the other isotope. This is consistent with expected isotope effects on chemical shifts. Based upon our preliminary findings, we suggest that the lUPAC chemical shift scale for both bromine isotopes may be converted to an equivalent scale for solids and that the solid-state bromine standard may be either NaBr(s) or KBr(s). If KBr(s) is used,... 

Invention of the laser provided the intense, monochromatic, tunable light source needed to make (diotochemical isotope separation apfdicabie to all elements, at least on a laboratory scale. The promise of this method was recognized as early as 1965 by Robieux and Audair [Rl], who were issued the first patent on it. Since the pioneering experiments of Tiffany et al. [Tl] on bromine isotopes in 1966, an enormous amount of work has been done with lasers, with small-scale separation reported for most elements. 

ECNI has proven to be highly sensitive, especially for compounds with more than four bromine atoms. The sensitivity for these compounds is approximately tenfold that obtained with ECD. Methane and ammonia have been used as reaction gases. GC or ECNI-MS spectra of most brominated compounds are dominated by the intense fragment ions of the bromine isotopes [ Br] and [ Br] found in the typical isotopic distribution of 0.505 to 0.495. Molecular ions or fragment ions at high mass are either scarcely found or found at very low intensity relative to the bromide ion. The drawback is that exclusive monitoring of m/z 79 and 81 allows no further identification of the hydrocarbon backbone of a brominated compound. However, some brominated compounds also... 

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