Displacement bromine

Chlorine has a lower electrode potential and electronegativity than fluorine but will displace bromine and iodine from aqueous solutions of bromide and iodide ions respectively ... 

Dimethothiazine, 374 Dimethoxanate, 390 Dimethylpyrindene, 145 Dimethylthiambutene, 106 Dimetridazole, 240 Dinoprost, 27, 33, 34 Dinoprostone, 27, 30, 33, 35 Dioscorea, see Mexican yam Diosgenin, 156, 182 Dioxyline, 349 Diphenhydramine, 41 Diphenidol, 45 Diphenoxylate, 302 Diphenylhydantoin, 246 Di phepanol, 46 Dipipanone, 80 Dipiproverin, 94 Dipyridamole, 428 Displacement, bromine by nitro, 247... 

The fluorine can be said to displace the chlorine from the compound, in the same way that chlorine displaces bromine or iodine... 

The electrochemical oxidation of bromoalkanes on platinum in anhydrous hydrogen fluoride displaces bromine by fluorine.27... 

Chlorine is used to displace bromine from brine that contains sodium bromide. Could oxygen in an acidified solution be used instead If so, why is it not used ... 

The commercial production of bromine from salt-well brines or from seawater depends on the fact that chlorine is capable of displacing bromine from its salts. Bromine is extracted from seawater by a process involving the following steps ... 

Several replacement reactions at C-4 in sydnones may be carried out but aqueous bases must be avoided. Butyllithium can be used to displace bromine from a 3-phenylsydnone the resulting organolithium salt can be carbonylated, will add to ketones, and forms a silyl derivative (80CB1830). A sydnone Grignard derivative can also be made and will add ketones in the normal way (80JCS(Pl)20). Sodium borohydride will reduce a sydnone sulfone, formed by oxidation of a thioether (Table 5) with hydrogen peroxide, back to the unsubstituted sydnone (74T409). 

JCS(C)1949 71JCS(C)3052 72JCS(P 1)265] in the latter two compounds, the displaced bromine substituted into starting material to give... 

In Section 19-11, we saw that direct alkylation is often a poor synthesis of amines, giving large amounts of overalkylated products. In this case, however, the reaction gives acceptable yields because a large excess of ammonia is used, making ammonia the nucleophile that is most likely to displace bromine. Also, the adjacent carboxylate ion in the product reduces the nucleophilicity of the amino group. The following sequence shows bromination of 3-phenylpropanoic acid, followed by displacement of bromide ion, to form the ammonium salt of racemic phenylalanine. 

OCH3 and NH3, give exclusive attack at the hard electrophilic centres, i.e. C—F, whereas soft nucleophiles displace bromine. This is further evidence for the importance of ion-dipole interactions, regarding attack at C—F bonds. Reactions of perfluoro-quinoline and -isoquinoline with hard and soft nucleophiles have also revealed a sensitivity towards a change in orientation of attack with the nature of the nucleophile [114] (Figure 9.42). 

Chlorine, Cl2feq) displaces bromine from MgBr2, so the missing species is free bromine,... 

A halogen higher in the periodic table is a stronger oxidizing agent than one lower down. Thus, chlorine can oxidize bromide ions or iodide ions from solution, and bromine can oxidize iodide ions. Here, chlorine displaces bromine ... 

Copper(I) cyanide in dimethylformamide displaces bromine in positions 5 or 6 of disubstituted imidazo[2,l-i][l,3,4]thiadiazoles (56) forming the corresponding heteroaromatic nitriles (Table 18) <83JHC1003, 88ZOR199). 

Triethylstibine dibromide, (C2Hg)3SbBr2, occurs when an alcoholic solution of the stibine is treated dropwise with a similar solution of bromine. It is purified by the method described for the dichloride. The dibromide is a colourless, strongly refractive liquid, density 1-953 at 17° C., solidifying to a snow-white mass at -10° C. It has a terpenoid odour, causes violent sneezing and is tear-exciting when warmed. In water it is insoluble, but solutions may be obtained in alcohol or ether. Concentrated sulphuric acid causes evolution of hydrobromic acid, and chlorine displaces bromine. 

Chlorine rapidly bleaches damp litmus paper. It will displace bromine from a solution of potassium bromide (then test for bromine by adding a suitable organic solvent such as hexane, which will show the brown bromine colour). 

The reactivity of the halogens decreases as the group is descended. Chlorine will displace bromine and iodine from bromides and iodides, respectively, and bromine will displace iodine from iodides. 

It has been found that the reaction at the C-Br or the C-Cl bond of l-bromo-4-chlorobutane can be controlled by changing the solvent for the reaction. For instance, the regiospeciflcity at the C-Br bond in the S 2 alkylation reaction with RZnBr in the presence of a Pd-PEPPSI-/-Pr catalyst when the DMI/THF ratio is 1/2 is 12.2 1 or 92%. DMI is dimethylimidazolidinone with an e = 37.6, whereas THF has an e = 7.5. However, when the DMI/THF = 2/1, the reaction occurs at the C—Cl bond. This means that the two reactions can be performed in one pot that is, one RZnBr reagent is used to displace bromine and, when this reaction is complete, the solvent composition is changed and a different RZnBr reagent is used to displace chlorine. Both reactions occur at room temperature, with yields of 70%. 

Consider the conversion of 64 to 65. The C-Br bond must be broken and water must attack the bromine-bearing carbon to form a C-0 bond. The experimental data show that this is not an 8 2 reaction, so water cannot displace bromine directly. The only way for the reaction to occur is for the C-Br bond to break first, which means that bromine must leave before water reacts. If true, then the OH in 65 arises fi om water, but if water reacts with carbon, the product is an oxonium ion, C-OH2h Therefore, 65 must arise from the oxonium ion, which arises fi"om the reaction of water with a carbocation intermediate. The carbocation must arise by loss of bromine fi om 64. This walk-through suggests the mechanism for this reaction. 

The a-phosphonoesters or ketones used in this variation of the Wittig reaction are formed by two successive reactions. Trimethylphosphite is an excellent nucleophile and readily displaces bromine from an a-bromoester or a-bromoketone by an reaction. Bromide ion then is the nucleophile in the second Sj 2 reaction that generates the a-phosphonoester. 

We say that chlorine has displaced bromine from solution. 

Figure 20.22 Aqueous chlorine displaces bromine from a solution of potassium bromide. We can use values to explain why a halogen higher in Group 17 displaces a halogen lower in the group from a solution of its halide ions.

The anion [(7T-Cp)W(CO)s] does not react with hexafluorobenzene, but displaces bromine from bromopentafluorobenzene, to give complex (54), and fluorine from tetrafluorophthalonitrile and pentafluoropyridine, to give complexes (55) and (56), suggesting that its nucleophilicity lies between that of [(ir-Cp)Mo(CO)3]- and of [Mn(CO)5]. The benzoyl complex (57) is formed from pentafluorobenzoyl chloride. 

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