Aldol-Dehydration Chemistry Using Aldehydes and Ketones | CHEM 2546, Study Guides, Projects, Research of Organic Chemistry

Download Aldol-Dehydration Chemistry Using Aldehydes and Ketones | CHEM 2546 and more Study Guides, Projects, Research Organic Chemistry in PDF only on Docsity! Aldol-Dehydration Chemistry Using Aldehydes and Ketones Biruk Mikru, Ryan Ritch, Shawn Trent, and Katie Wooten Objectives • To utilize aldol-dehydration chemistry and Brady’s reagent to identify unknown aldehydes and ketones. O R 2 R 1 H Aldol Claisen-Schmidt Condensation • Type of aldol addition • Named after the two scientists: Ludwig Claisen and J. G. Schmidt • This reaction however uses two molecules of esters to make a β-keto ester. CH3 O O R 2 O CH3 O R O β -Keto ester Brady’s Reagent • 2,4-Dinitrophenylhydrazine (2,4-DNPH) mixed in Methanol or Sulfuric Acid (H2SO4) • Used to detect aldehyde or ketone • The addition of an alcohol, acetone and an acid in to both the ketone and aldehyde, will produce orange precipitant • Indicates the presence of carbonyl functional group, i.e. double bond between carbon and oxygen. 2,4-Dinitrophenylhydrazine Aldol Reactions in Nature • The formation of cross-linked collagen (protein of connective tissue) between two collagens to make the linkage stronger. Procedure React unknown aldehyde and ketone Weigh product and take melting point Perform crystallization on unknown aldehyde and unknown ketone with 2,4-dinitrophenylhydrazine Take melting point Compare the products with possible unknown Compare the product to possible dehydration products Week 1 Week 2 Observations: Step I (Week 1) • Unknown Aldehydes and Ketones – Clear liquids – Produced “sweet” odors • Ethanol – Clear liquid – Used as a solvent • Sodium Hydroxide (NaOH) – Clear liquid solution – Used as a base catalyst • Toluene – Clear and flammable liquid – Used as a solvent Observations: Step I (cont.) • After the addition of NaOH – Two layers were formed – Top Layer: yellow tint and oily – Bottom Layer: clear and contained white solid • Stirring Process – Solution became cloudy after 10 minutes – Solid was observed after 15 minute stirring and the solution appeared yellow and cloudy Observations: Step 2 (cont.) • Test Tube A (Aldehyde) – Red-orange Crystalline Product. • Test Tube B (Ketone) – Yellow Crystalline Product. • Ethanol: – Clear Flammable Liquid – Used for Washing Product • Recrystallization – Dissolved Product In Solvent – Heating Solution and Evaporating Solvent Results/Discussion: Step I • Aldol-Dehydration – Aldehyde A + Ketone 1: • .533 g of product • Melting Point: 100-103 C° • Melting point similar to the product of 4- methylcyclohexanone and benzaldehyde – Aldehyde B + Ketone 2: • .90 g of product • Melting Point: 133 – 135 C° • Melting point similar to the product of 4- methylcyclohexanone and 4-methylbenzaldehyde Table of Literature Melting Points for Step 1 MP of Aldol-Dehydration | Ketones products (°C) Aldehydes Acetone | Cyclopentanone | Cyclohexanone} 4-methylcyclohexanone Benzaldehyde 113 189 118 98-99 4-methy Ibenzaldehyde 175 235-236 170 133-135 4-methoxylbenzaldehyde | 129-130 212 159 41-142 E-3-phenyl-2-propenal 144 225 180 163-164 NMR Data for Aldol Dehydration Product of Aldehyde B and Ketone 2 Conclusion • Step II results for aldehyde B and ketone 2 confirmed Step I results – 4-methylbenzaldehyde – 4-methylcyclohexanone • Results for aldehyde A and ketone 1 were unsatisfactory. – Experimental Error – Improper Drying – Incorrect MP Identified Unknowns oO H SS O° 4-methylbenzaldehyde 4-methylcyclohexanone Works Cited Anslyn, Eric V and Dennis A Dougherty. Modern Physical Organic Chemistry . University Science Books, 2006. Paula, Yurkanis and Bruice. Organic Chemistry. Upper Saddle River: Pearson Printice Hall, 2007. Richter, Victor Von, Richard Anschütz and Georg Schroeter. Victor Von Richter's Organic Chemistry; Or, Chemistry of the Carbon Compounds. Ann Arbor: P. Blakiston's sons & co, 1900. Shriner, R, et al. The Systematic Identification of Organic Compounds. New York: Wiley, 1980. Works Cited Ctd. • “The Use of 2:P-Dinitrophenylhydrazine as a Reagent for Aldehydes and Ketones.” www.rsc.org/ejarchive/AN/1926/AN9265100077.pdf Accessed 04/13/08 • Many personal conversations with Stephanie Antolak