I Bromide

Submitted by R. J. Clark, Ernest Griswold, and Jacob Kleinberg Checked by Richard D. BarnesJ and John D. CohbettJ 

Previous methodsfor the preparation of indium (I) bromide, as well as other indium monohalides and the dihalides, have utilized two main approaches. Either the metal was halogenated with free halogen or hydrogen halide under the appropriate conditions, or indium tri- 

The procedure described below for the preparation of indium(I) bromide is extremely simple. Moreover, by appropriate variation of the stoichiometry of the reactants, it can be used for the preparation of indium dibromide. The preparation consists of the reaction of indium metal with mercury(II) bromide at an elevated temperature in a sealed evacuated tube. Mercury (I) bromide can be used in place of the mercury(II) compound. The same method can also be used for the synthesis of the chlorides and iodides of lower-valent indium.  

The reaction is carried out in a 20 X 0.8-cm. piece of thick-walled Pyrex tubing which has a small well of 8-mm. tubing sealed about 6 cm. from the closed end of the tube. One and fifteen-hundredths grams (0.01 mol) of indiumf and 1.80 g. (0.005 mol) of mercury(II) bromide are weighed into the reaction tube. The tube is then evacuated to a pressure of 10 to 15/i, sealed, and heated to 350° in a muffle furnace for about 30 minutes. The mercury set free is separated from the molten indium (I) bromide by removing the tube from the furnace and carefully tilting it so that the mercury runs into the well. To ensure complete 

A series of preparations gave products having the following bromide to indiumf atomic ratios 1.01, 1,06, 1.07, 1.03, 1.00. 

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Bromine is used in the manufacture of many important organic compounds including 1,2-dibromoethane (ethylene dibromide), added to petrol to prevent lead deposition which occurs by decomposition of the anti-knock —lead tetraethyl bromomethane (methyl bromide), a fumigating agent, and several compounds used to reduce flammability of polyester plastics and epoxide resins. Silver(I) bromide is used extensively in the photographic industry... 

Thirty minutes after refluxing had stopped, a trace of copper(I) bromide was added to terminate the conversion. The reaction mixture was cautiously poured on to 500 g of finely crushed ice, then 200 ml of 4 N hydrochloric acid were added. After the remaining ice had melted the layers were separated and the aqueous layer was extracted three times with diethyl ether. The combined ethereal solutions were washed with saturated NaCl solution and dried over magnesium sulfate. The greater part of... 

To a mixture of 0.30 mol of l-diethylamino-4-methoxy-2-butyne (see Chapter V, Exp. 15) and 175 ml of dry diethyl ether were added 2.5 g of copper(I) bromide. 

To a mixture of 100 ml of THF and 0.10 mol of the epoxide (note 1) was added 0.5 g Of copper(I) bromide. A solution of phenylmagnesium bromide (prepared from 0.18 mol of bromobenzene, see Chapter II, Exp. 5) in 130 ml of THF was added drop-wise in 20 min at 20-30°C. After an additional 30 min the black reaction mixture was hydrolysed with a solution of 2 g of NaCN or KCN and 20 g of ammonium chloride in 150 ml of water. The aqueous layer was extracted three times with diethyl ether. The combined organic solutions were washed with water and dried over magnesium sulfate. The residue obtained after concentration of the solution in a water-pump vacuum was distilled through a short column, giving the allenic alcohol, b.p. 100°C/0.2 mmHg, n. 1.5705, in 75% yield. 

To 200 ml of 48% hydrobromic acid was added 0.40 mol of phosphorus tribromide (note 1). The mixture was agitated vigorously, while the temperature was kept between 20 and 30 0 by cooling in a water-bath at 10-15 0. After about 1 h the lower layer had disappeared completely. The solution was cooled to 0°C, then 0.40 mol of ammonium bromide, 0.10 mol (note 2) of copper(I) bromide (commercial product),... 

To a mixture of 0.10 mol of 1-ethoxy-l,2-heptadiene (see this chapter, Exp. 13) and 120 ml of diethyl ether was added 1 g of copper(I) bromide. A solution of butyl magnesium bromide in about 200 ml of diethyl ether, prepared from 0.25 mol of butyl bromide (see Chapter II, Exp. 5) was added in 15 min. The reaction was weakly exothermic and the temperature rose slowly to about 32°C. The mixture was held for an additional 40 min at that temperature, then the black reaction mixture was... 

Although It IS possible to prepare aryl chlorides and aryl bromides by electrophilic aromatic substitution it is often necessary to prepare these compounds from an aromatic amine The amine is converted to the corresponding diazonmm salt and then treated with copper(I) chloride or copper(I) bromide as appropriate... 

Furan and thiophene undergo addition reactions with carbenes. Thus cyclopropane derivatives are obtained from these heterocycles on copper(I) bromide-catalyzed reaction with diazomethane and light-promoted reaction with diazoacetic acid ester (Scheme 41). The copper-catalyzed reaction of pyrrole with diazoacetic acid ester, however, gives a 2-substituted product (Scheme 42). 

Neopentyl (2,2-dimethylpropyl) systems are resistant to nucleo diilic substitution reactions. They are primary and do not form caibocation intermediates, but the /-butyl substituent efiTectively hinders back-side attack. The rate of reaction of neopent>i bromide with iodide ion is 470 times slower than that of n-butyl bromide. Usually, tiie ner rentyl system reacts with rearrangement to the /-pentyl system, aldiough use of good nucleophiles in polar aprotic solvents permits direct displacement to occur. Entry 2 shows that such a reaction with azide ion as the nucleophile proceeds with complete inversion of configuration. The primary beiuyl system in entry 3 exhibits high, but not complete, inversiotL This is attributed to racemization of the reactant by ionization and internal return. 

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