Bromide resemblance

It should be noted that these reactions are analogous to those which take place between alkyl halides and water and alkalies. The effect of the presence of two halogen atoms is to make it possible for the reactions to take place much more rapidly and at a lower temperature. Other reactions in which ethylene bromide resembles the alkyl halides are those which take place with ammonia and potassium cyanide... 

Cyanogen bromide is prepared by reacting metal cyanides with bromine in water or carbon tetrachloride. The properties of cyanogen bromide resemble those of interhalogens (a compoimd formed by several halogens). When it reacts with... 

Iodine bromide and arsenic(III) bromide resemble closely as solvents iodine monochloride and arsenic(III) chloride respectively, and stable acids have not been isolated in the bromo-systems. Molten mercury(II) bromide is an excellent solvent for various classes of compounds. Alkali metal bromides form solvated anionic species which appear to contain the ions [IBr2] , [AsBr4] and [HgBr3] respectively and phosphorus(V) bromide gives PBr4+IBr2 in iodine bromide where it behaves as a base. Other basic substances are nitrogenous bases such as pyridine. 

The iodides of the alkaU metals and those of the heavier alkaline earths are resistant to oxygen on heating, but most others can be roasted to oxide in air and oxygen. The vapors of the most volatile iodides, such as those of aluminum and titanium(II) actually bum in air. The iodides resemble the sulfides in this respect, with the important difference that the iodine is volatilized, not as an oxide, but as the free element, which can be recovered as such. Chlorine and bromine readily displace iodine from the iodides, converting them to the corresponding chlorides and bromides. 

As with oxathianes 3 (R1 = CH, R2 = H), which bear a close structural resemblance to 17, the addition of organometallic reagents is highly diastereoselective with a predominant chelation-controlled attack of the nucleophile from the Rc-sidc35 -40. In the case of vinylmagnesium bromide a considerable enhancement of the diastereo selectivity could be attained by adding... 

The Markovnikov regioselectivity of the gem-alkenes is associated with a chemoselectivity. in favour of methanol attack, significantly greater than that observed for the other alkenes. If no sodium bromide is added to the reaction medium, no dibromide is observed for this series. Therefore, these alkenes behave as highly conjugated olefins, as regards their regio- and chemo-selectivity. In other words, the bromination intermediates of gem-alkenes resemble P-bromocarbocations, rather than bromonium ions. Theoretical calculations (ref. 8) but not kinetic data (ref. 14) support this conclusion. 

X-ray structural information on halide binding to neutral organic it-receptors is limited to a few recent reports [23,24,62,89-91 ]2. In fact, the slow diffusion of hexane into a dichloromethane solutions of tetracyanopyrazine containing the alkylammonium salts of either chloride, bromide or iodide affords yellow to red crystals with UV-Vis absorptions closely resembling the elec-... 

The behaviour of the tram-3-bromide 38 closely resembled that of its cyclopentyl analogue 32. Thus with silver oxide only the cis-2-bromo-[3.2.1]peroxide 40 expected for a SN2 ring closure was obtained, and although some 40 was also formed in the reaction of 38 with silver trifluoroacetate, the predominant (90 %) bicyclic peroxide obtained was 41, i.e. the [3.2.1]peroxide available via a bromonium ion mechanism. The behaviour of the tran.v-4-bromide 39 was very revealing, for it did not react with silver oxide and 41 was the only bicyclic peroxide formed with silver trifluoroacetate. 

As a result of the inductive and hyperconjugative effects it is to be expected that tertiary carbonium ions will be more stable than secondary carbonium ions, which in turn will be more stable than primary ions. The stabilization of the corresponding transition states for ionization should be in the same order, since the transition state will somewhat resemble the ion. Thus the first order rate constant for the solvolysis of tert-buty bromide in alkaline 80% aqueous ethanol at 55° is about 4000 times that of isopropyl bromide, while for ethyl and methyl bromides the first order contribution to the hydrolysis rate is imperceptible against the contribution from the bimolecular hydrolysis.217 Formic acid is such a good ionizing solvent that even primary alkyl bromides hydrolyze at a rate nearly independent of water concentration. The relative rates at 100° are tertiary butyl, 108 isopropyl, 44.7 ethyl, 1.71 and methyl, 1.00.218>212 One a-phenyl substituent is about as effective in accelerating the ionization as two a-alkyl groups.212 Thus the reactions of benzyl compounds, like those of secondary alkyl compounds, are of borderline mechanism, while benzhydryl compounds react by the unimolecular ionization mechanism. 

The polymers from Experiments R8, R15 and R9 contained ca. 1 tritium atom, and therefore originally 1 aluminium-carbon bond, per molecule. For those experiments in which the polymer remained in solution, the final value of the conductivity suggested a minimum of 1 mol of ions for 1 mol of polymer. When aluminium chloride was used as initiator, the results obtained resembled closely those obtained with the bromide. 

Kantarjian AD, Shasheen AS. 1963. Methyl bromide poisoning with nervous system manifestiations resembling polyneuropathy. Neurology 13 1054-1058. 

Compared to many other types of synthetic intermediates, acetylides, RC=CM (M = Li, Na, K), show a moderate reactivity towards alkyl halides in the usual organic solvents E O and THF and in liquid ammonia [2], In this respect acetylides resemble enolates >C=COM. In the absence of dipolar aprodc co-solvents (DMSO or HMPT), lithium alkynylides, RC=CLi, react sluggishly in Et O or THF with most alkyl halides [2]. In liquid ammonia the alkylation of alkali acetylides with the lower (up to C-5) alkyl bromides or iodides proceeds at a satisfactory rate [5]. A certain amount of DMSO added to the reaction mixture increases the solubility of halides with a longer carbon chain. A second effect of the addition of this co-solvent is that the temperature of the reaction mixture can gradually rise as more ammonia evaporates. In this way, the reaction can proceed gradually over the range from -33 C (b.p. NH3) to room temperature. Specific alkylation on the acetylenic carbon takes place if an equivalent amount of an alkyl halide is added to dilithiated propargvl alcohol in liquid ammonia... 

Aatimonious bromide, SbBr resembles antimonious chloride i it fhses at 00, boils at 270 , and by the action of water is converted into the oagbromide, SbOBr. 

The bromide, [Cr(NH3)2(H20)2Br2]Br, is obtained as an intensely green crystalline powder from Reinecke s salt by oxidation with bromine from trithiocyanato-diammino-aquo-chromium, [Cr(NH3)2H20(SCN)3] or from dianimino-tetraquo-ehromic bromide.4 It resembles the dichloro-derivative in reactions. 

Diammino-uranyl Bromide, [U02(XH3)2]Br2, is prepared by passing ammonia gas through a solution of uranyl bromide in amyl alcohol till the solution is decolorised and a flocculent yellow precipitate is produced on drying in vacuo the substance is obtained as a yellow amorphous powder, hr properties it resembles the chloride. An ether derivative, of composition [UO2(XH3)2]Cl2.C2H100, is formed if ammonia is passed into an ethereal solution of uranyl bromide. Tri-ammino-uranyl bromide, [U02(XH3)3]Br2, and tetrammino -uranyl bromide, [U02(XH3)4]Br2, are prepared by an analogous method to that for the preparation of the corresponding chlorides, and the properties are similar. 

The bromide, [Co en2H20.0H]Br2.H20, is obtained from the chloride or from iraws-dichloro-diethylenediamino-cobaltic chloride by treating it with concentrated aqueous potassium hydroxide and, after cooling to 0° C., neutralising the solution obtained with concentrated hydrobromie acid. It is a red crystalline powder, and resembles the chloride in properties. 

It separates in small violet rhombic crystals which resemble chloro-pentammino-cobaltic chloride in appearance. It is soluble in cold water to a certain extent, and only two-thirds of the chlorine is precipitated from solution by silver nitrate at ordinary temperature. In aqueous solution the salt is gradually transformed into the diaquo-salt, [Co(NH3)4(HaO)2]Cl3 dilute nitric acid, if rubbed with the substance, gives reddish-violet crystals of the nitrate, [Co(XH3)4(HaO)Cl](NOs)2 and a cold concentrated solution of ammonium sulphate yields the sulphate, [Co(NH3)4(H20)C1]S04. The corresponding bromide, [Co(NH3)4(H2Q)Cl]Br2, is obtained by filtering a cold saturated solution of the chloride into concentrated hydrobromie acid at 0° C. The precipitate formed is washed with hydrobromie acid and then with alcohol. The bromide is almost insoluble in hydrobromie acid, but more easily soluble in water than the chloride.2... 

Trihydrazino-nickel Chloride, [Ni(N2H4)3]Cl2, is obtained by treating hexammino-niekel chloride with 50 per cent, aqueous hydrazine hydrate. On heating the mixture ammonia is evolved, and the hydra-zino-salt precipitated as a violet crystalline powder which dissolves in dilute acids, giving a blue solution. The corresponding hy drazino -compounds of nickel bromide are prepared in the same manner from nickel bromide and hexammino-niekel bromide. They are crystalline substances, and resemble the clilorides in appearance and in reactions. 

The aquo-salts are extremely easily hydrolysed, and even moistening with water causes them to decompose, with formation of the less soluble liydroxo-salts. Alcohol also causes hydrolysis of the compounds. The behaviour of the salts towards water resembles that of the diaquo-dipyridino-diammino-cobaltic salts. Thus, the bromide, HaO py2 i... 

The bromide, [Rh(NH3)6]Br3, is prepared by the addition of concentrated hydrobromic acid to a solution of the chloride or the nitrate. It crystallises in thin hexagonal plates, and is less soluble than the chloride, which it resembles in reactions. 

Hexammino-iridium Bromide, [Ir(NII3)6]Br3, is formed by treating a solution of the nitrate with hydrobromie acid. It crystallises in colourless six-sided prisms which resemble the chloride, only they are more soluble in water. 

The bromide, [ Ir (Nil 3) 4CI2] Br. H 20, is prepared by the addition of concentrated livdrobromic acid to a warm solution of the chloride, when the crystalline compound separates. It is recrystallised from warm water and obtained in yellow needles or prisms which resemble the chloride. It loses water at 80° C. 

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