CBSE CHEMISTRY PRACTICALS CLASS-XII-2
Identification of functional groups in organic compounds
EXPERIMENT: 1
Tests for the functional groups present in organic compounds:
Aim: To identify the functional groups present in an organic compound:
Apparatus and chemicals required:
Test tube and test tube stand, Droppers, spatula and water bath (use 50 mL glass beaker as water bath), Organic compound. And Bromine reagent, Bayer’s reagent.
Tests for Unsaturation
There are two tests for determining unsaturation in an organic compound.
Procedure:
1. Bromine Test
Dissolve 0.1 g or 5 drops of organic compound in 2 mL of carbon tetrachloride in a test tube and add 2% solution of bromine in carbon tetrachloride or bromine water drop by drop with continuous shaking.
Observation:
The orange-red color of bromine solution remain same no color change is observed
Inference:
An unsaturated organic compound (unsaturated hydrocarbon) is absent
May be saturated organic compound may be present, May be alcohol or carboxylic acid is present.
2. Baeyer’s Test (Alkaline KMnO4 Test)
Procedure: Dissolve 25-30 mg of organic compound in 2 mL of water (free of alcohol) and add 1% potassium permanganate solution containing equal volume of 1% sodium carbonate solution. Observation:
Pink color of KMnO4 not disappeared.
Inference: unsaturated organic compound is absent may be saturated organic compound ethanol may be may be present.
Precautions:
(a) The tests should be performed at room temperature. (b) Handle bromine solution carefully. Do not inhale the vapors and also avoid its contact with the skin.
Tests for Alcoholic Group:
The alcoholic group can be detected by the following tests:
Procedure:
1. Sodium metal test
Take 3ml of given organic compound in a dry test tube add 1g of CaCl2 to it then filter it. Then add a piece of sodium metal to the filtrate.
Observation:
Alcohols react with active metals like sodium and liberate hydrogen gas that can be observed in the form of effervescence.
Inference:
May be Alcohol or phenol or ethanoic acid present.
2. Ester test:
Procedure: Take about 0.1 g compound in a test tube, add 1 mL ethanol or methanol and 2-3 drops of concentrated sulphuric acid. Heat the reaction mixture for 10-15 minutes in a hot water bath at about 50°C. Pour the reaction mixture in a beaker containing aqueous sodium carbonate solution to neutralize excess sulphuric acid and excess carboxylic acid.
Observation: Sweet smell of the substance formed
Inference: the presence of -OH functional group in the compound.
3. Ceric ammonium nitrate test:
Procedure:
Take 1 mL solution of organic compound dissolved in a suitable solvent. Add a few drops of ceric ammonium nitrate solution. Alcohols reacts with ceric ammonium nitrate to form a red colored alkoxy cerium (IV) compound.
Observation: Appearance of red color.
Inference: Alcohol ethanol (-OH) is confirmed.
Experiment-2
Aim:
The phenolic group can be detected by the following tests:
1. Litmus test
Phenol is a weak acid, it gives red colour with litmus paper. The dissociation of phenol in water is represented as follows:
2. Ferric chloride test
Take 2 mL of aqueous or alcoholic solution of the organic compound in a test tube, add neutral ferric chloride solution dropwise and note the color change.
Observation: Phenol reacts with ferric ions to form violet colored complex.Appearance of a blue, green, violet or red color
Precautions: (a) Always use freshly prepared, neutral and very dilute solution of ferric chloride. (b) Phenol is toxic and corrosive in nature and should be handled with care.
3.Phthalein Dye test
Take 0.1 g of organic compound and 0.1 g of phthalic anhydride in a clean dry test tube and add 1-2 drops of conc. H2SO4. Heat the test tube for about 1 minute in an oil bath. Cool and pour the reaction mixture carefully into a beaker containing 15 mL of dilute sodium hydroxide solution.
Observation: Appearance of pink, blue, green, red etc. colors.
Inference: the presence of phenolic –OH group in the compound is confirmed.
Experiment-3 and 4:
Carbonyl groups in aldehydes and ketones are identified by the following tests:
Aim: To identify the presence of functional group in given organic compound.
Procedure:
1. 2, 4-dinitrophenyl hydrazine test (2,4-DNP test):
Take 2-3 drops of the liquid compound in a test tube or in case of solid compound, dissolve a few crystals of it in 2-3 mL alcohol. Add a few drops of an alcoholic solution of 2,4-dinitrophenylhydrazine
Observation:
Appearance of yellow, orange or orange-red precipitate.
Inference: confirms the presence of carbonyl group.
If precipitate does not appear at room temperature, warm the mixture in a water bath for a few minutes and cool.
Test for aldehyde:
2. Sodium bisulphite test
Procedure:
Take a saturated solution of sodium bisulfite in a clean test tube. Add 1ml of the given organic compound. Shake well and leave it for 15-20 minutes.
Observation:
White precipitate is observed.
Inference: The presence of the carbonyl group is confirmed.
Note: Acetone phenone and benzophenone do not give this test.
1. Schiff’s Test:
Procedure:
Take 3-4 drops of the liquid compound or dissolve a few crystals of organic compound in alcohol and add 2-3 drops of the Schiff’s reagent.
Observation: Appearance of pink color.
Inference: Presence of Aldehyde is confirmed.
Note: With benzaldehyde the pink color develops slowly.
2.Tollen’s Test
Procedure:
Take 1 mL of freshly prepared (~ 2 %) silver nitrate solution in a test tube. Add 1-2 drops of sodium hydroxide solution to it and shake, a dark brown precipitate of silver oxide appears. Dissolve the precipitate by adding ammonium hydroxide solution drop-wise.
Heat the reaction mixture of step (ii) in a water bath for about 5 minutes.
Observation: Formation of a layer of silver metal on the inner surface of the test tube.
Inference: the presence of an aldehyde is confirmed.
3. Fehling’s Test
Procedure:
Take nearly 1 mL of Fehling’s solution A and 1 mL of Fehling’s solution B in a clean dry test tube. To this add 2-3 drops of the liquid compound or about 2 mL of the solution of the solid compound in water or alcohol. Heat the content of the test tube for about 2 minutes in a water bath.
Observation:
Formation of brick red precipitate is observed.
Inference: the presence of aliphatic an aldehyde.
Precautions: Always use freshly prepared reagents to perform the tests. (b) Do not heat the reaction mixture directly on a flame. (c) After performing the test, destroy the silver mirror by adding dilute nitric acid and drain off the solution with excess of water.
Test for Ketones:
1. m-dinitrobenzene Test
Procedure:
Take 2ml of given organic compound add 0.5g of solid m-nitrobenzene and add few drops of Aqueous solution of sodium hydroxide and shake the contents.
Observation: A violet coloration is appeared. After sometime it faded away.
Inference: Ketone functional group confirmed.
2. Sodium nitroprusside Test
Procedure:
Take 2ml of given organic compound in a test tube add 1ml of sodium hydroxide solution followed by sodium nitro-presside solution.
Observation: The anion of the ketone formed by a alkali reacts with nitroprusside ion to form a red colored complex.
Inference: Ketone functional group is confirmed.
Experiment: 5
Tests for Carboxylic group
Aim: To identify the functional group present in given organic compound.
The following tests can be used to identify carboxylic acids:
1. Litmus Test:
Take 2ml of given organic compound in dry test tube dip blue litmus paper in solution.
Observation: Blue litmus solution changes to red color.
Inference: May be carboxylic acid present or phenol.
2. Sodium Hydrogen Carbonate Test
Procedure: take 2ml of given organic compound in dry test tube and add 0.5g of sodium hydrogen carbonate.
Observation: A colorless gas which can be seen in the form of a brisk effervescence.
Inference: - COOH functional may be present.-OH functional group is absent.
3. Ester Test
Procedure: take 2ml of given organic compound into a dry test tube add equal quantity of ethanol and few drops of concentrated sulphuric acid and heat on water bath for 5 minutes.
Observation: a fruity smell will be observed.
Inference:-COOH Functional group is confirmed.
Experiment-6
Tests for Amines:
Aim :To identify the functional group present in given organic compound.
1. Solubility Test:
Procedure:
Take 1 mL of given organic compound in a test tube and add a few drops of dilute H Cl to it. Shake the contents of the test tube well.
Observation: the organic compound dissolves in dilute H Cl.
Inference: it shows the presence of an amine.
2. Litmus Test
Amines are basic in nature and turns red litmus blue.
3. Carbylamines Test:
Procedure:
Take 2-3 drops of the compound in a test tube and add 2-3 drops of chloroform followed by addition of an equal volume of 0.5 M alcoholic potassium hydroxide solution. Heat the contents gently.
Observation: An obnoxious smell is evolved.
Inference: the presence of primary amino group in the given organic compound.
4. Azo-Dye Test
Procedure:
Dissolve nearly 0.2 g of the compound in 2 mL of dilute hydrochloric acid in a test tube. Cool the content of the test tube in ice.
(ii) To the ice cooled solution add 2 mL of 2.5% cold aqueous sodium nitrite solution.
(iii) In another test tube, dissolve 0.2 g of β-naphthol in dilute sodium hydroxide solution.
(iv) Add diazonium chloride solution prepared in step (ii) into the cold β-naphthol solution slowly with shaking.
Observation: The formation of a scarlet red dye will be observed.
Inference: confirms the presence of aromatic primary amine.
Chemistry Projects
List of chemistry projects for class -12
Projects for class 12 Chemistry
PROJECTS
Scientific investigations involving laboratory testing and collecting information from other sources A few suggested Projects.
Projects from chemistry in day life:
1. Role of Paracetamols and Hydroxyl chloroquine in controlling COVID -19 pandemic conditions.
2. Need of Azithromycin and vaccine in COVID -19 Pandemic situations.
3. Role of disinfectants in controlling and prevention of spread of viral and bacterial diseases. (Sanitizers and soaps, Dettol’s)
4. Study of the presence of oxalate ions in guava fruit at different stages of ripening.
5. Study of quantity of casein present in different samples of milk.
6. Preparation of soybean milk and its comparison with the natural milk with respect to curd formation, effect of temperature, etc.
7. Study of the effect of Potassium Bisulphate as food preservative under various conditions (temperature, concentration, time, etc.)
8. Study of digestion of starch by salivary amylase and effect of pH and temperature on it.
9. Comparative study of the rate of fermentation of following materials: wheat flour, gram flour, potato juice, carrot juice, etc.
10. Extraction of essential oils present in Saunf (aniseed), Ajwain (carum), Illaichi(cardamom). 11. Study of common food adulterants in fat, oil, butter, sugar, turmeric power, chilli powder and pepper.
Note: Any other investigatory project, which involves about 10 periods of work, can be chosen with the approval of the teacher.
Sample project
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