Bromine solution

For class work it is convenient to make up a single bromine solution by dissolving 7 ml. of bromine in 100 ml. of glacial acetic acid, and using 6-5 ml. of this solution for each preparation. 

Dibromide formation. Dissolve 0 2 ml. of styrene in 0 5 ml. of CCI4 in a test-tube. Add slowly, drop by drop, a 10% solution of bromine in CCI4. Note the decolorisation of the bromine and absence of HBr fumes (therefore reaction by addition and not by substitution). Continue to add the bromine solution until a faint brown colour persists. Scratch the sides of the tube and cool it in ice-water. Filter off the crystals that separate and recrystallise the styrene dibromide from methanol m.p. 72 . 

For ammonium bromide, another method involving reaction of an aqueous bromine solution and Hon filings has been used. The solution of ferrous and ferric bromide thus formed then reacts with ammonia to precipitate hydrated oxides of Hon. Ammonium bromide can be recovered by crystallization from the concentrated Hquor. 

Analysis. Butenes are best characterized by their property of decolorizing both a solution of bromine in carbon tetrachloride and a cold, dilute, neutral permanganate solution (the Baeyer test). A solution of bromine in carbon tetrachloride is red the dihaUde, like the butenes, are colorless. Decoloration of the bromine solution is rapid. In the Baeyer test, a purple color is replaced by brown manganese oxide (a precipitate) and a colorless diol. These tests apply to all alkenes. 

Benzoyl azide Biphenyl triozonide Boron tribromide Bromine azide Bromine solutions... 

Sorbic acid Treat with bromine solution or bromine vapor di-, tri- and tetrabromocaproic acids are produced. [47]... 

To a solution of 80 mg of 1-(/3-D-arabinofuranosyl)-2-thiocytosine in 12 ml of water is added dropwise 3 ml of a 1 M bromine solution in carbon tetrachloride. At this point the color of the bromine persists for about 2-3 minutes after each addition. The unreacted bromine is blown off with a stream of nitrogen, and the reaction mixture is concentrated to a syrup in vacuo using a bath temperature less than 50°C. The residue is evaporated three times with 10 ml portions of ethanol, whereupon it crystallizes. The product is triturated with cold ethanol and with ether to obtain 17 mg of 2,2 -anhydro-1 -(/3-D-arabinofuranosyl)cytosine hydrobromide, MP 240°C (dec.). 

It is essential to maintain the temperature of the solution below 25° during the addition of the bromine solution. If external cooling is applied, initially with an ice-water bath, the addition can be completed within 20 minutes. 

Halogenatlon. Poly(2,6-dimethyl- and 2,6-diphenyl-l,4-phenylene ether) can be aryl-brominated simply by exposure to a bromine solution no catalyst is required.6 In fact, the use of Lewis acid catalysts to promote the chlorination of poly(2,6-dimethy1-1,4-phenylene ether) leads to substantial degradation of the molecular weight of the chlorinated products.7 Membranes produced from ring brominated PPO (40% wt Br) exhibited enhanced permeability to CHi and CO2 and proved to be more selective in separating CH4/CO2 mixtures.8... 

Method of Preparation Dissolve 1 g of phenol and 4 mL of liquid Br2 separately in 10-15 mL of glacial acetic acid. Add Br2 solution to phenol solution until the decolourisation of bromine ceases. Allow the mixture to stand for 20 min and add more bromine solution, if the colour faded. Pour the liquor into 70 mL of water and filter the product. Wash with water and recrystallise in ethanol. 

Molybdenum (IV) bromide is a black crystalline solid which is very sensitive to oxidation and hydrolysis it should be handled only under a dry inert atmosphere. Its solubility in bromine at 51° is ca. 3.0 g./lOOO g. of bromine, and bromine solutions were found to be nonconductors. For example, at 25° both the solvent bromine and a 0.96 X 10 3 M solution in molybdenum (IV) bromide exhibited a specific conductance of 1.3 X 10-10 ohm-1 cm.-1 At 110 to 130° in vacuo, solid molybdenum (IV) bromide decomposes quantitatively into molyb-denum(III) bromide and bromine, and because of this thermal instability it cannot be sublimed except under a bromine atmosphere. 

Bromine solution was prepared by shakinp liquid bromine in water at room temperature in closed plass vessels and suitably diluted. The details of the bromine and ammonia stapes were given in a previous publication [8],... 

A. 2-Ami/no-S-bromopyridine. In a 2-1. three-necked flask equipped with stirrer, dropping funnel, and condenser is placed a solution of 282 g. (3.0 moles) of 2-aminopyridine (Note 1) in 500 ml. of acetic acid. The solution is cooled to below 20° by immersion in an ice bath, and 480 g. (154 ml., 3.0 moles) of bromine dissolved in 300 ml. of acetic acid is added dropwise with vigorous stirring over a period of 1 hour. Initially the temperature is maintained below 20°, but after about half the bromine solution has been added it is allowed to rise to 50° to delay as long as possible the separation of the hydrobromide of 2-amino-5-bromopyridine. At 50° the hydrobromide usually begins to crystallize when about three-quarters of the bromine has been added. When addition of bromine is completed, the mixture is stirred for 1 hour and is then diluted with 750 ml. of water to dissolve the hydrobromide. The contents of the flask are transferred to a 5-1. beaker and are neutralized, with stirring and cooling, by the addition of 1.2 1. of 40% sodium hydroxide solution. 

Now keep the solution of the base cool in ice and rapidly run in bromine solution with continuous shaking. Observe that the fine red colour attains its maximum when about 25 c.c. of the bromine solution have been added, but that after the addition of 25 c.c. more the colour becomes much lighter. Because of secondary reactions a pure yellow colour is never produced as a rule, yet a little more bromine must be added rapidly. When the loss of colour has ceased run in stannous chloride solution immediately. After 25 c.c. have been added the beautiful colour of Wurster s red returns, only to... 

Materials Required Thyroid gland dried 1.0 g anhydrous potassium carbonate 17.0 g bromine solution (9.6 ml of Br2 and 30 g of KBr in 100 ml DW) 7.0 ml dilute phosphoric acid (10% w/v) 42.0 ml starch iodide paper phenol solution (saturated solution of phenol in water) 5.0 ml potassium iodide solution (10% w/v in water) 0.01 N sodium thiosulphate solution starch solution. 

This involves the preparation of 0.1 N bromine solution and subsequent standardization with 0.1 N sodium thiosulphate solution. Bromine solution is also known as Koppeschaar s Solution in some literature. 

Materials Required 0.1 N Bromine solution hydrochloric acid ( 11.5 N) 5 ml potassium iodide solution (10% w/v in water) 5.0 ml 0.1 N sodium thiosulphate starch solution. 

Procedure Transfer 25 ml of 0.1 N bromine solution with the help of a pipette into a 500 ml iodine flask and dilute it with 120 ml of DW. Add to it 5 ml of hydrochloric acid, moisten the glass-stopper with water and insert the stopper in the flask. Shake the contents gently. Now, add 5 ml of potassium iodide solution, again lace the stopper and allow the resulting mixture to stand for 5 minutes in the dark. Titrate the liberated iodine with previously standardized 0.1 N sodium thiosulphate solution, adding 3 ml of freshly prepared starch solution towards the end-point. Each ml of 0.1N sodium thiosulphate is equivalent to 0.01598 g... 

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