CHEM 324 - Exp. 47.pdf - Experiment 47 Synthesis of Dimedone and Measurement of Its Tautomeric Equilibrium Constant Hang Tran 40044938 Concordia

CHEM 324 - Exp. 47.pdf - Experiment 47 Synthesis of...

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Experiment 47 Synthesis of Dimedone and Measurement of Its Tautomeric Equilibrium Constant Hang Tran 40044938 Concordia University Chem 324 – Thursday Afternoon Date Submitted: 11/15/2019
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Introduction The purpose of this experiment is to synthesize dimedone. This will be performed through formation of enolates and cyclization to form a 6 membered ring. The reactions taking place during this synthesis are Michael addition as well as Dieckmann cyclization. [1][5] The synthesis will be performed using mesityl oxide and dimethyl malonate as the starting materials. Mesityl oxide will act as the Michael acceptor in the addition while dimethyl malonate will be the soft nucleophile attacking. A self-Claisen condensation will follow resulting in cyclization and formation of a 6-membered ring with ketone and ester functional groups. The resulting compound will then undergo a hydrolysis reaction to form the final product, dimedone. An important technique used in this lab recrystallization to remove impurities. This is a very common technique used to purify organic solids. This technique generally consists of dissolving a crude solid in a hot suitable solvent and then allowed to cool to recrystallize final, pure product. [2] The removal of impurities happens during the dissolving step in the hot solvent and during the crystallization step in the cooled solvent. Impurities are separated from the pure crystals during vacuum filtration for collection of final product. [2] The basis of recrystallization
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depends on the fact that as temperature increases, the solubility of a solid in a solvent increases. Thus, when the recrystallization solution cools, the solubility of the pure solid and its impurities are different which allow for separation of the two. Observations & Raw Data Week 1 - When dimethyl malonate and sodium methoxide were mixed, solution was thick, viscous and white - Once heated, the solution clumped up into one solid and slowly melted as temperature increased - When mesityl oxide was added, the solution became yellow and everything dissolved - Reflux turned the solution into a dark yellow liquid - In the Rotovap, the solution turned solid, pale yellow and foamy - Once NaOH was added, the solid dissolved into a light amber solution - Refluxing for 45 minutes and solution remained a light amber - Once HCl was added, the solution turned into a light-yellow colour - Once removed from heat, the solution cooled, and crystals precipitated - When crystals were forming, there were some oily bits as well - Vacuum filtration yield a white/yellow powdery solid
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