بسم الله الرحمن الرحيم UMM AL-QURA UNIVERSITYFaculty of MedicineDep. Of BIOCHEMISTRY
To identify organic compounds from their odors and the colors of their reaction products. OBJECTIVES:
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. Odors:
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. Experiment S:
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.
ABDULLATIF TAHA ABDULLAMSc. BIOCHEMISTRY سبحانك لا علم لنا إلا ما علمتنا * إنك أنت العليم الحكيم 0 QUESTIONS?