E Alexander Chem 130l Lodine Lodide Test Add 2 Drops Of Iodine Potassium Iodide To 2 Ml Of Each Of The Seven Carbohyd 1 (77.96 KiB) Viewed 23 times
E Alexander Chem 130l Lodine Lodide Test Add 2 Drops Of Iodine Potassium Iodide To 2 Ml Of Each Of The Seven Carbohyd 2 (42.86 KiB) Viewed 23 times
E Alexander Chem 130l Lodine Lodide Test Add 2 Drops Of Iodine Potassium Iodide To 2 Ml Of Each Of The Seven Carbohyd 3 (54.28 KiB) Viewed 23 times
E. Alexander CHEM 130L lodine-lodide Test. Add 2 drops of iodine-potassium iodide to 2 ml. of each of the seven carbohydrate solutions. Note the color changes after mixing. Barfoed's Test. Barfoed's reagent is useful in differentiating between reducing monosaccharides and reducing disaccharides. Place 3 mL of Barfoed's reagent and I mL of the carbohydrate solution in a test tube and place the tube in a beaker of boiling water for 5 minuets (no longer!). After heating, remove the test tube and cool it in running water. A dark red precipitate of cuprous oxide is a positive test for a reducing monosaccharide. Bial's Test. This test can be used to distinguish between pentose's and hexoses. CAUTION: This test uses concentrated (12 M) HCI which can cause severe skin burns. Immediate washing of the affected area and prompt reporting to the instructor are important to avoid skin burns if the hydrochloric acid is spilled. Place 3 mL of Bial's reagent and 2 drops of the 1% carbohydrate solution in a test tube and place the tube in a beaker of boiling water and heat. Remove each tube as soon as you see a color change. A pentose will provide a green or blue color within 2 minucts. The muddy brown or grey color develops from-a-ketose or disaccharide containing a ketohexose. Benedict's Test. Benedict's test is used to identify reducing sugars. Add 10 drops of each of the seven 1% carbohydrate solutions to 3 mL of Benedict's solution contained in individual test tubes. Place all seven tubes in boiling water at the same time, and remove them after exactly 2 minuets. A dark red precipitate of cuprous oxide is a positive test. Seliwanoff's Test. This test can be used to distinguish between aldohexoses and ketohexoses. CAUTION: This test uses concentrated (6 M) HC1 which can cause severe skin burns. Immediate washing of the affected area and prompt reporting to the instructor are important to avoid skin burns if the hydrochloric acid is spilled. Place 10 drops of each carbohydrate solution, 15 drops of distilled water, and 9 mL of Seliwanoff's reagent into test tubes. Place in a beaker of boiling water, and heat no longer than a cherry-red product; aldoses give a blue-green solution. Part B- Hydrolysis of Carbohydrates The properties of hydrolyzed carbohydrates are compared with those of the unhydrolyzed parent material. For this part unsolubilized starch (corn starch) and sucrose are used. Acid-Catalyzed Hydrolysis of Sucrose. Add 1 mL of 3 M hydrochloric acid to 10 mL of 1% sucrose solution. Place the mixture into a beaker of boiling water, and heat for 30 minuets. Cool the solution, and neutralize it to litmus with 3 M sodium hydroxide. Test the neutralized solution
CHEM 130L E. Alexander with Benedict's reagent. Run concurrently another Benedict's test on unhydrolyzed sucrose. Use the procedure for Benedict's test in Part A. Acid-Catalyzed Hydrolysis of Corn Starch. Mix 2 g of corn starch with 20 mL of cold water and crunch the lumps with a stirring rod. Pour the suspension slowly into a beaker containing 250 mL of boiling distilled water. Boil the mixture for an additional 2 minuets, and allow it to cool. Hydrolyze 10 mL of the corn starch solutions as follows. Add 1 mL of 3 M hydrochloric acid, and heat the mixture in a beaker of boiling water for 30 minuets. Cool the solution, and neutralize it to litmus with 3 M sodium hydroxide solution. Perform the Benedict's test and the 12-KI Test as described in Part A. Perform each test simultaneously on the unhydrolyzed cornstarch solution and on the hydrolyzed cornstarch solution. Compare the results.
Sellwan off's test c. Maltose and mannose Benedict's maltese d. Sucrose and lactose Barfoed's test e. Sucrose and starch Iodine test. 2.) What structural features do all reducing sugars have in common? All reducing sugars have the presence of Open aldehydic/Ketonic reagents that reduce the tollen's reagent. 3.) Explain why sucrose reacts rapidly with Seliwanoff's reagent. Sucrose reacts rapidly with seliwanoff's reagent because it is the only non-reducing disaccharide known, Sucrose is also a xetuse so it gets dehydrated faster during the test, allowing fast results. 4.) Explain the changes you observed in the 12-KI test and the Benedict's test for corn starch and hydrolyzed corn starch. 5.) A compound does not react with Barfoed's solution. It gives a brown color with the Bial solution and a cherry color with Seliwanoff solution. Draw a structure for the compound. CH₂OH sucrose H 15 X OH HO CH 2016 НО OH H 12 OH
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