بسم الله الرحمن الرحيم

 To identify organic compounds from their odors and the colors of their reaction products.

Many organic compounds give characteristic odors as follows:  Pleasant odor: ethers, esters.  Pungent odor: carboxylic acids, acetic acid, acid chloride, acid anhydride, acetic anhydride and amines: pyridine.  Phenolic odor: many phenols and derivatives of salicylic acid.  Almond odor: benzaldehyde, benzonitrile and nitrobenzene.

 Many organic compounds give characteristic colors of their reaction products.  The above odors and colors help in identification of at least classes of organic compounds. Colors of Reaction Products:

 Test for Halides: Add 2 ml. of AgNO3 to 1 ml. of methyl iodide and shake. A yellow precipitate of AgI is formed in the cold.  Test for Alcohols: Add 3 ml. of KI and 10 ml. of NaOCl to 0.5 ml. of ethanol and warm gently. Fine yellow crystals of iodoform separate.  Test for Ethers: Add a few crystals of iodine to 3 ml. of diethyl ether. Iodine dissolved in the ether giving a brown color.

 Test for Aldehydes: Add 3 drops of NaOH to 3 ml. of AgNO3 in a test tube. Add ammonia solution drop by drop until the precipitate of silver oxide is almost re-dissolved and then add 3 drops of formaldehyde. A silver mirror is formed.  Test for Ketones: Add 1 ml. of sodium nitroprosside to 0.5 ml. acetone in a test tube. Add NaOH in excess; a red coloration is produced.  Test for Carboxylic Acids: Add NaOH to FeCl3 solution in a test tube untill a small permanent precipitate of Fe(OH)3 is produced. Use the filtrate as neutral FeCl3 solution. Place 0.5 g of acetic acid in a test tube and add slight excess of NH3 solution until just alkaline to litmus paper. Add a piece of unglazed porcelain and boil until NH3 is removed and then cool. To the solution so obtained add a few drops of neutralized FeCl3 solution; A deep red coloration is produced.

 Test for Esters: To a few drops of ethyl acetate add 0.2 g hydroxylamine- hydrochloride and about 5 ml. of NaOH and gently boil for 1-2 min. cool and acidify with HCl and then add a few drops of FeCl3 solution. A violet or deep red-brown color develops immediately.  Test for Acid chloride: Acidify 2 ml. of AgNO3 with HNO3 and then add acetyl chloride solution drop by drop with shaking. A white precipitate of AgCl is produced.  Test for Nitrobenzene: To a very dilute solution of nitrobenzene (1%) in a test tube, add few drops of FeCl3 solution. A reddish coloration is produced.  Test for Phenol: To a very dilute solution of phenol (1%) in a test tube, add a drop of FeCl3 solution. A violet coloration is produced.

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