Polarography of polyhalogen-substituted benzyl bromides and the corresponding benzylmercuric bromides

Conclusions On the basis of a comparison of the polarographic behavior of a series of polybromine-substituted benzylmercuric bromides and the corresponding substituted benzyl bromides it was shown in the case of benzyl bromides active in the preparative reaction with metallic mercury that the reduction takes place through the initial formation of organomercury compounds at the surface of the mercury electrode.Translated from Izvestiya Akademii Nauk SSSR. Seriya Khimicheskaya, No. 3, pp. 546–548, March, 1985.     

Photodissociation of alkyl bromides

The branching ratios for the production of Br(4²P_{$\text{1}\text{2}$}) following the broadband flash photolysis of the alkyl bromides, CH₃Br and C₂H₅Br, and the perfluorinated molecules, CF₃Br, C₂F₅ Br and n-C₃F₇ Br, have been determined using time-resolved atomic absorption spectroscopy. The production of electronically excited bromine atoms is shown to be inefficient in the case of the alkyl bromides while the perfluorinated molecules yield decreasing amounts of Br(4²P_{$\text{1}\text{2}$}) as the molecular complexity increases, i.e., CF₃Br > C₂F₅Br > C₃F₅Br > C₃F₇. It is also shown that the hydrogenated bromides deactive electronically excited atoms almost two orders of magnitude faster than do the perfluorinated bromides.     

Thermal diffusion of alkali bromides

The molar entropies (or heats) of transport of dilute aqueous alkali bromide solutions have been measured by the potentiometric method using the silver, silver bromide thermocell at a mean temperature of 25°C and over a concentration range of 5×10^–4 to 0.1M. Experimental results were extrapolated to infinite dilution to obtain the standard molar entropies of transport. The limiting behavior observed is compared with theory based on the electrostatic model.The standard transported entropy of Br^– was also derived by extrapolating the steady-state thermoelectric powers to infinite dilution. The absolute ionic entropies of transport of alkali metal ions have been estimated based on Gurney's scale. The results obtained are compared with that derived f¹/om the previous work on alkali chlorides.     

Anticorrosive properties of N-acetylmethylpyridinium bromides

The inhibiting action of N-acetylmethylpyridinium bromides on the corrosion of low-carbon steel in a 3 M sulfuric acid solution at 20, 40, 60, and 80°C was studied. The mechanism of their protective action was examined using electrochemical methods. Compounds exhibiting high anticorrosive properties at elevated temperatures were found.     

N,n-Dialkyldiazenium bromides in the diene synthesis

The diene synthesis with N, N-dialkyldiazenium bromides affords a method for the preparation of 1, 1-dialkyl ⁴-tetrahydropyridazinium salts.     

Diffusion of water in solutions of alkali metal bromides,tetraalkylammonium bromides and ammonium bromide

The diffusion coefficient of water D _w in aqueous solutions of the alkali metal bromides, tetraalkylammonium bromides (methyl, ethyl, n-propyl, and n-butyl) and ammonium bromide at 25°C is reported for concentrations up to 2 mol-dm^–3. In addition, values for D _w in 2 mol-dm^–3 solutions of CsBr, KBr, NaBr, LiBr, and fully deuterated methanol, acetonitrile, and acetone have been measured for temperatures in the range 5 to 50°C. The concentration dependence of the relative water diffusion coefficient D _w /D _o , where D _o is the self-diffusion coefficient of water, has been analyzed in terms of an equation analogous to the Jones-Dole equation for relative viscosity. The B-coefficient for diffusion is well correlated with the viscosity B-coefficient. For the structure-breaking electrolytes CsBr and KBr, D _w /D _o decreases rapidly with increasing temperature, whereas for the structure-makers NaBr and LiBr, the temperature dependence of D _w /D _o has the same sign but is much smaller in magnitude. For the nonelectrolyte solutions, the structure-making effect decreases with increasing temperature and the temperature coefficient of D _w /D _o is positive. It is apparent that, when diffusion of the solvent is being considered, the temperature must be taken into account in the classification of an electrolyte as a structure-breaker or structure-maker.     

2,6-Lutidine-N-oxide complexes of rare-earth bromides

2,6-Lutidine-N-oxide (LNO) complexes of rare-earth bromides of the composition wheren = l for M = La, Pr, Nd, Sm, Gd, Ho, Er; andn = 0 for M = Y have been prepared and characterised by analyses, conductance and infrared data. Infrared spectra of the complexes indicate that the coordination of ligand to the metal ion takes place through the oxygen of the ligand, and the water molecule in the complexes present is coordinated to the metal. A coordination number of seven has been suggested to all the rare-earth metal ions.     

The mesomorphic behaviour of cyanopropylalkyldimethylammonium bromides

Abstract

A homologous series of N-cyanopropyl-N-alkyl-N,N-dimethylammonium bromides was synthesized and characterized. Its thermotropic liquid crystalline behaviour was studied by differential scanning calorimetry, polarizing optical microscopy, dilatometry, and X-ray diffraction. A smectic A mesophase was thus identified. The smectic layers were found to be formed of two ionic planes alternately separated by sub-layers of disordered alkyl chains and cyanopropyl groups. The smectic structure was compared with that of the crystal at room temperature and also that of the smectic T structure of the N,N-dialkyl-N,N-dimethylammonium bromides already described in the literature.     

A photoelectron study of the alkali bromides and iodides

Precise values have been determined for the binding energies of the outer electronic bands of the alkali bromides and iodides using 40.81 eV ultraviolet photoelectron spectroscopy. These values have been corrected for relaxation effects and then favourably compared with the Born model for ionic solids in terms of both the absolute values of binding energy and the energy separation between the outer valence bands.     

Reactions of halogenoquinolizinium bromides with diethylamine

The reactions of quinolizinium bromide (QB) and its four monobromo derivatives with diethylamine have been investigated. For Br in position 2 or 4, substitution is the main process, whereas for Br in positions 1 and 3 quantitative ring opening is found. The substituted pyridylbutadienes formed by ring opening, are cis-trans-butadienes, which isomerize into the all-trans forms. The steric cours of the ring opening is explained.     

Interaction of adenosine with alkyltrimethylammonium bromides

The interaction of adenosine with alkyltrimethylammonium bromides, C_mH_2m+1N(CH₃)₃Br(m=16, 14, 12, 10, 8, and 6), has been studied by 1 H NMR spectroscopy. When surfactants exist as monomer units, the adenine ring of adenosine preferentially associates with the middle portion of the alkyl chain of the surfactants. The interaction is less specific with surfactants of shorter alkyl chains. When surfactants form micelles, no specific interaction between the adenine ring and the alkyl chain of the surfactant can be detected. A coordination of the cationic part of the surfactants with the adenine ring is suggested. The degree of association was evaluated from association constants. Similar results were obtained for purine and alkyltrimethylammonium bromide.     

Palladium-catalyzed carbene insertion into benzyl bromides

Palladium can catalyze the insertion of ethyl diazoacetate into benzyl bromides. The key step in the catalytic cycle is the migratory insertion of a carbene, derived from ethyl diazoacetate, into a Pd-C bond.     

Palladium-catalyzed borylation of primary alkyl bromides

A mild Pd-catalyzed process for the borylation of alkyl bromides has been developed using bis(pinacolato)diboron as a boron source. This process accommodates the use of a wide range of functional groups on the alkyl bromide substrate. Primary bromides react with complete selectivity in the presence of a secondary bromide. The generality of this approach is demonstrated by its extension to the use of alkyl iodides and alkyl tosylates, as well as borylation reactions employing bis(neopentyl glycolato)diboron as the boron source.