Tollen\'s and Benedict\'s Paper PDF

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Tara Straub CHM 112: Fund. of Biological Chemistry Dr. Solsky 10 Mar. 2021 Tollen’s Test and Benedict’s Test Tollens’ test, commonly referred to as the silver-mirror test, is a qualitative laboratory test used to distinguish between an aldehyde and a ketone. It exploits the fact that aldehydes are readily oxidized, whereas ketones are not (OChemPal). One thing about Tollen’s test that is important to note is that it utilizes a reagent known as Tollen’s reagent, “...which is a colorless, basic, aqueous solution containing silver ions coordinated to ammonia” (Libretexts). The reagent consists of “...a solution of silver nitrate, ammonia and some sodium hydroxide” (Wikimedia Foundation). If Tollen’s test is positive, a silver mirror will appear in the test tube, indicating the presence of an aldehyde. When an aldehyde is introduced to the Tollens reagent, the aldehyde is oxidized by the Tollens reagent and forms a carboxylic acid (BYJU’s contributors). Ketones are not oxidized by Tollens’ reagent, so the treatment of a ketone with Tollens’ reagent in a glass test tube does not result in a silver mirror (OChemPal). The types of compounds that result in a positive Tollen’s test include all aldehydes. Benedict’s Test is another test that utilizes aldehydes and ketones. The purpose of this test is to detect reducing sugars, and it can also be used to detect the presence of glucose in blood and urine. In the medical community, this test is important because it aids in helping identify diabetes and glycosuria (U.S. National Library...). Benedict's reagent starts out as an aqua-blue color. As it is heated in the presence of reducing sugars, it turns yellowish-orange. In general, blue to blue-green or yellow-green is indicative of a negative test, yellowish to bright yellow

indicates a moderately positive test, and bright orange to red is a very strong positive test (Organic Molecules Review). The chemical makeup of Benedict’s reagent consists of a complex mixture of sodium carbonate, sodium citrate and copper (II) sulfate pentahydrate (Admin.). The type of compounds that give a positive test for the Benedict's reagent include glucose, fructose, and ribose (Admin.).

References Admin. (2020, October 21). Benedict's Test - Reagent Preparation, Principle, Procedure, Reaction. BYJUS. https://byjus.com/chemistry/benedicts-test/. Benedict's test: Definition, Principle, uses, and reagent. (2020, September 21). https://www.chemistrylearner.com/benedicts-test.html. BYJU’s contributors. (2020, October 5). Tollens test - description and preparation of tollens reagent. https://byjus.com/chemistry/tollens-test/. Libretexts. (2020, September 13). Tollens Test. https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Org anic_Chemistry)/Aldehydes_and_Ketones/Reactivity_of_Aldehydes_and_Ketones/Tollens _Test. OChemPal. http://www.ochempal.org/index.php/alphabetical/s-t/tollens-test/. Organic Molecules Review. Lab Review. https://www.nku.edu/~whitsonma/Bio150LSite/Lab%203%20Organic/Bio150LRevMolec. html. U.S. National Library of Medicine. (2020, July 31). Glucose in Urine Test: MedlinePlus Medical Test. MedlinePlus. https://medlineplus.gov/lab-tests/glucose-in-urinetest/#:~:text=If%20high%20levels%20of%20glucose,a%20diagnosis%20of%20gestational %20diabetes. Wikimedia Foundation. (2021, January 26). Tollens' reagent. Wikipedia. https://en.wikipedia.org/wiki/Tollens%27_reagent#:~:text=The%20reagent%20consists%2 0of%20a,the%20German%20chemist%20Bernhard%20Tollens....