Sodium bromide, reaction

Equip a 3 litre three-necked flask with a thermometer, a mercury-sealed mechanical stirrer and a double-surface reflux condenser. It is important that all the apparatus be thoroughly dry. Place 212 g. of trimethylene dibromide (Section 111,35) and 160 g. of ethyl malonate (Section 111,153) (dried over anhydrous calcium sulphate) in the flask. By means of a separatory funnel, supported in a retort ring and fitted into the top of the condenser with a grooved cork, add with stirring a solution of 46 g. of sodium in 800 ml. of super dry ethyl alcohol (Section 11,47,5) (I) at such a rate that the temperature of the reaction mixture is maintained at 60-65° (50-60 minutes). When the addition is complete, allow the mixture to stand until the temperature falls to 50-55°, and then heat on a water bath until a few drops of the liquid when added to water are no longer alkaline to phenolphthalein (about 2 hours). Add sufficient water to dissolve the precipitate of sodium bromide, and remove the alcohol by distillation from a water bath. Arrange the flask for steam distillation (Fig. this merely involves... 

The formation of alkylbenzenes, largely free from unaaturated compounds, provides another interesting application of organosodium compounds. Thus pure M-butylbenzene is readily obtained in good yield from benzyl sodium and n-propyl bromide. Benzyl-sodium is conveniently prepared by first forming phenyl-sodium by reaction between sodium and chlorobenzene in a toluene medium, followed by heating the toluene suspension of the phenyl-sodium at 105° for about 35 minutes ... 

Recall that the term kinetics refers to how the rate of a reaction varies with changes m concentration Consider the nucleophilic substitution m which sodium hydroxide reacts with methyl bromide to form methyl alcohol and sodium bromide... 

The oxidative reaction of furan with bromine in methanol solution or an electrochemical process using sodium bromide produces 2,5-dimethoxy-2,5-dihydrofuran (19), which is a cycHc acetal of maleic dialdehyde. The double bond in (19) can be easily hydrogenated to produce the corresponding succindialdehyde derivative. Both products find appHcation in photography and as embalming materials, as well as other uses. 

Unsaturation value can be determined by the reaction of the akyl or propenyl end group with mercuric acetate ia a methanolic solution to give acetoxymercuric methoxy compounds and acetic acid (ASTM D4671-87). The amount of acetic acid released ia this equimolar reaction is determined by titration with standard alcohoHc potassium hydroxide. Sodium bromide is normally added to convert the iasoluble mercuric oxide (a titration iaterference) to mercuric bromide. The value is usually expressed as meg KOH/g polyol which can be converted to OH No. units usiag multiplication by 56.1 or to percentage of vinyl usiag multiplication by 2.7. 

Halothiophenes. The biomothiophenes, coimneicially the most impoitant of the halothiophenes, are readily made and can be further derivatized. Manufacture of 2-bromothiophene involves the reaction of thiophene with a solution of sodium bromide/sodium bromate in acid solution. 

Commercial manufacture of methyl bromide is generally based on the reaction of hydrogen bromide with methanol. For laboratory preparation, the addition of sulfuric acid to sodium bromide and methanol has been used (80). Another method involves the treatment of bromine with a reducing agent, such as phosphoms or sulfur dioxide, to generate hydrogen bromide (81). 

There have been a number of cell designs tested for this reaction. Undivided cells using sodium bromide electrolyte have been tried (see, for example. Ref. 29). These have had electrode shapes for in-ceU propylene absorption into the electrolyte. The chief advantages of the electrochemical route to propylene oxide are elimination of the need for chlorine and lime, as well as avoidance of calcium chloride disposal (see Calcium compounds, calcium CHLORIDE Lime and limestone). An indirect electrochemical approach meeting these same objectives employs the chlorine produced at the anode of a membrane cell for preparing the propylene chlorohydrin external to the electrolysis system. The caustic made at the cathode is used to convert the chlorohydrin to propylene oxide, reforming a NaCl solution which is recycled. Attractive economics are claimed for this combined chlor-alkali electrolysis and propylene oxide manufacture (135). 

Complexes 59 or 60 enter the chloride displacement reaction with sodium bromide and iodide. The products obtained are analogs of isomer 59. Pyiazole,... 

Methylphenyl)benzothiazole (80IC762) and 2-benzylbenzothiazole (95ICA(239)125) can be cyclopalladated. In the latter case, cylopalladation occurs upon reaction with palladium(II) acetate and gives the product 80. With lithium chloride, sodium bromide, or sodium iodide, a series of three products of substitution of the acetate group 81 (X = C1, Br, I) results. Pyridine, 2- and 3-methylpyridine, 2,6- and 3,5-dimethylpyridine cause the transformation of the chelate complexes 81 (X = C1, Br, I) and formation of the mononuclear products 82 (R = z= R" = = R = H, X = Cl, Br, I ... 

The heat of reaction brought about refluxing during the addition of the 2-bromo-3-hexyne, and when the addition was complete the reaction mixture was heated to refluxing for a further period of 30 minutes. A sufficient amount of water was then added to the reaction mixture to dissolve the sodium bromide which had formed, and the only organic layer was separated, washed with water and dried over anhydrous magnesium sulfate. The dried organic layer was then fractionally distilled under reduced pressure, and the diethyl (1-methyl-2-pentynyl) malonate formed in the reaction was collected at about 117° to 120°C at the pressure of 2 mm of mercury. 

Butylation of ethyl phenylacetate, /-butyl phenylacetate, and ethyl 2-phenylhexanoate has also been accomplished with M-butyl bromide and sodium hydride in refluxing monoglyme in 64%, 66%, and 56% yields, respectively.6 In contrast to the sodium amide reactions above, however, careful fractionation of the crude products was required to obtain pure products. 

We can use these bromine compounds to illustrate one kind of organic reaction. Ethyl bromide is not particularly reactive but it does react with bases such as NaOH or NH3. If we mix ethyl bromide and aqueous sodium hydroxide solution and heat the mixture for an hour or so, we find that sodium bromide and ethanol are formed. 

We have seen that oxidation is electron loss and reduction is electron gain. Electrons are real particles and cannot just be "lost. Therefore, whenever a species is oxidized, another species must be reduced. Oxidation or reduction considered separately is like one hand clapping one transfer must occur in conjunction with the other for reaction to take place. For instance, in the reaction between chlorine and sodium bromide, the bromide ions are oxidized and the chlorine... 

We see that magnesium has been oxidized and chlorine has been reduced. Similarly, in the reaction between sodium bromide and chlorine,... 

Methanol containing 0.2 M sodium bromide was chosen as the reaction medium. Bromide ions were added to obtain better precision on chemoselectivity since, in the absence of external bromide, the yield of dibromo adduct can be very small. The results of this investigation are shown in Table 1. 

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. 

Recycle traditionally involves caustic scrubbing the gaseous HBr from bromination reactions (eqn. 3). The resulting sodium bromide solution is then treated with chlorine gas to generate bromine (eqn. 4). 

These reactions are useful because they run under mild conditions, use inexpensive or easily recoverable starting materials, and have short reaction times. The major problem in purification is the separation of the sodium pyridone sulfonate from excess sodium sulfite, sodium bromide, and sodium bromoalkyl sulfonate. However, these latter compounds usually would not interfere with the use of the pyridone sulfonate as a water tracer. From a practical point of view, the pyridone sulfonates need not be purified, but can be used directly. A modified synthetic procedure involves the treatment of the pyridone sodium salt with a tenfold excess of a,iu-dibromoalkane in acetonitrile, followed by removal of the excess dibromide by vacuum distillation. The resulting product is treated with an excess of sodium sulfite in aqueous ethanol. Evaporation of the solvent yields a useful tracer. Procedures given in the experimental section were... 

When equal volumes of 0.100 M solutions of sodium bromide and silver nitrate are mixed, a white solid precipitates from the solution. Identify the precipitate, write the net ionic reaction for the solubility equilibrium, and identify any spectator ions. 

An alternative ambient temperature design based on sodium ion reaction refers to the domain of the so-calledbatteries. The polysulfide bromide cell (PSB) provides a reversible electrochemical reaction between two salt solution electrolytes (sodium bromide and sodium polysulfide), according to the scheme... 

The submitter reports that an equivalent number of moles of Y-bromobutyronitrile or a mixture of 7-chloro- and 7-bromo-butyronitrile may be substituted for 7-chlorobutyronitrile. If the bromo compound is used the reaction mixture should be refluxed six hours and it is necessary to filter off the sodium bromide just before the final vacuum distillation. 

---