Bromine-water test

The bromine water test is somewhat more satisfactory for pure tryptophane than the glyoxylic acid test. Hydrogen sulfide may interfere (owing to sulfur formation) and must be boiled out first. The solution to be tested must be acid with acetic acid. 

Rgure 10.71 The bromine water test for unsaturated hydrocarbons. The unsaturated hydrocarbon decolorizes the bromine water the saturated compound does not... 

The sulfonic acid group in phenols and amines may often > displaced by halogen in connection with the usual bromine-water test. 

Bromine. Slip the glass cover of a jar momentarily aside, add 2-3 ml. of bromine water, replace the cover and shake the contents of the jar vigorously. Note that the bromine is absorbed only very slowly, in marked contrast to the rapid absorption by ethylene. This slow reaction with bromine water is also in marked contrast to the action of chlorine water, which unites with acetylene with explosive violence. (Therefore do not attempt this test with chlorine or chlorine water.)... 

Extract the acidified solution with ether, remove the ether and identify the phenol in the usual manner (see Section IV,114).f Add a few drops of bromine water or nitric acid to the aqueous layer and test for sulphate with barium chloride solution. 

Pure Commercial Benzene, obtained from coal-tai naphtha, should distil w lthin one degiee (80—Si ), and solidify completely when cooled to 0°. Other tests are as follow s shaken with concentrated sulphuric acid for a few minutes, the acid should not darken, and a drop of bromine water should not be immediately decolourised. A single distillation over a few small pieces of sodium, which absorb any traces of water, is usually a sufficient purification. If the benzene impart a brown or black colour to the sulphuric acid, it must be repeatedly shaken with about 20 per cent, of the acid until the lattev becomes only slightly yellow on standing. This is done in a stoppered separating funnel, and after shaking fora few minutes the mixture is allow ed to settle, and the low er layer of acid diawn off. The benzene is then shaken tw o 01 three times with water to free it from acid, carefully separated from the aqueous layer, and left in contact with fused calcium chloride until the liquid becomes clear. It is then decanted, frozen in ice, and any liquid (carbon bisulphide, paraffins) carefully drained off, and die benzene finally distilled over sodium. 

They react with a solution of bromine in carbon tetrachloride by substitution and an equivalent quantity of hydrogen bromide is evolved (compare addition with unsaturated compounds). When the test is conducted with bromine water and a dilute aqueous solution of a phmiol, the sim of reaction is the separation of a sparingly soluble bromine substitution product. ... 

A set of Pacific open-ocean samples were analysed for iodate-iodine using both the procedure which incorporates pre-oxidation with iodine water and that which does not. Also, in a similar exercise total iodine was determined using both the method that incorporates pre-oxidation with bromine water and the catalytic method using the reaction between Ce(IV) and As(III) [81]. Variance tests showed that differences between either replicates or methods was not significant. 

Next, drops of bromine water, chlorine water and iodine water were mixed in samples of mineral oil and the color of the oil and evidence of a reaction were recorded in the Table 2 below. Also tested was the halide ion mixed with mineral oil. 

The product is tested for the presence of phosphorus (PC13) by decomposing a few drops with a little warm water and evaporating the solution in a porcelain capsule. The residue is twice evaporated with concentrated nitric acid or with bromine water and is finally tested for phosphoric add in the usual way. If phosphorus is detected, the material should again be distilled with a few drops of glacial acetic acid. 

Since it does not reduce Tokens or Fehltng reagent, (A) must be a ketone. (A) responds to iodoform test. Therefore, it should be a methyl ketone. The molecular formula of (A) Indicates high degree of unsaturation, yet it does not decolourise bromine water or Baeyer s reagent. This indicates the presence of unsaturation due to an aromatic ring. 

Tryptophane is not obtained in any large amount by the hydrolysis of proteins by acids and is best prepared by the action of trypsin. According to Hopkins and Cole, the protein is digested in alkaline solution by trypsin, until the solution gives a maximal coloration when tested with bromine water the solution is then acidified, boiled and... 

Add 3-5 ml of water into a test tube with bromine and stir its contents with a glass rod. What is observed Is the solubility of bromine in water high What is called bromine water Add a few drops of a saturated potassium bromide solution to this tube containing bromine water and stir its contents. Explain what occurs. 

Pour 2-3 ml of bromine water into a test tube and add a sodium hydroxide solution. How can the change in the colour of the solution be explained Write the equation of the reaction. 

Pour several drops of bromine water into a test tube, dilute it with 5 ml of distilled water, and add 5-10 drops of chloroform. Thoroughly stir the contents of the test tube. Explain the observed phenomenon. Perform a similar experiment with other organic solvents (petrol, benzene, carbon disulphide, carbon tetrachloride). 

Pour bromine water, chlorine water, and acidified solutions of potassium permanganate and dichromate into separate test tubes. Pass a stream of hydrogen snlphide through all the tubes. What happens Write the equation of the reactions. What property of hydrogen sulphide is indicated by the occurring phenomena ... 

Cobalt(in) Hydroxide. Pour a cobalt(ll) salt solution into two test tubes, add bromine water to one of them, hydrogen peroxide to the other, and then pour a sodium hydroxide solution into both tubes. What happens Write the equations of the reactions. 

Pour 1-2 ml of a tin(II) chloride solution into each of two test tubes. Add a little bromine water to the first tube. How does the colour of the solution change Add sulphurous acid to the second tube. What do you observe Write the equations of the reactions. What properties of tinfll) compounds do these reactions indicate ... 

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