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Synthesis of benzil Renan Gongora Spring 2017 Outline • Tetracyclone • Retrosynthesis O • Alcohol Oxidation • Acyloin Condensation • Ylide • Benzoin • Acyloin Condensation • Reflux • Recrystallization H 2O H 2O • Analyze Crude • Caclulate % yield • Get into pairs 2 2 Tetracyclone Used to make Shvo’s Catalyst (top structure) Oxidative coupling of primary alcohols to esters Oxidation of alcohols to form ketones Aldehyde, ketone and imine hydroboration O O Recall how low your yield was for the isopentyl acetate lab, this method could increase yield O You’re not making this but you could Brian L. Conley, Megan K. Pennington-Boggio, Emine Boz, and Travis J. Williams "Discovery, Applications, and Catalytic Mechanisms of Shvo’s Catalyst" Chemical Reviews, 2010, volume 110, pp. 2294–2312. doi:10.1021/cr9003133 3 Retrosynthesis O Imagine if you wanted to make this compound, how could I make it using simple/inexpensive materials? O O O O OH O 4 Synthesis: The next two weeks (separate lab reports) H 2N N O S H 2N N S O O OH N N N N OH OH H2O/EtOH 1:3 v/v This week!! HNO3 O Synthesis 1) Reflux in acid 2) Quench with Water 3) Purify O O OH O HNO3 benzoin Oxidation benzil Which carbon was oxidized? Protip: You can determine if a carbon has been oxidized if there are less hydrogen atoms connected to it or if there are more oxygen atoms connected to it. 6 Procedure O OH (2.5 g) Only start refluxing after setup has been approved! H 2O HNOOH (12 mL) (10 mL) 3 H 2O 50 mL RBF set up NaOH reflux with gas trap 7 7 Procedure Only start refluxing after setup has been approved! H 2O H 2O NaOH ≈60 mins or until no more NO2 (g) cool to r.t. O crude Stir unitl crystallization If no crystals form cool with an ice bath (40 mL) Vacuum Filter Washing with cold DI water twice (25 mL) (10 mL) SLOWLY quench with cool DI water and pour reaction mixture into OH (10 mL) water O OH Procedure filter to Vacuum dispose filtrate in acid waste Recrystallization O O O OH Recall the purpose of your select solvent is At elevated temperatures: completely dissolve your product but At lower temperatures: your product should be i_s_l_b_e Procedure O O O OH under ice bath until crystals form enough EtOHOHjust(10 mL) (≈0.5g/5mL of EtOH) OH (10 mL) 100 mL RBF MILDLY heat NaOH until completely dissolved sit at r.t. 11 Recrystallization Procedure O O O OH Vacuum Filter Weigh Washing with cold filter EtOH (5 m LX 2) paper O O before this step to Vacuum DI H 2O EtOH (you calculate this volume) 12 Recall Reflux • Prevents solvent loss H 2O H 2O • Prevents buildup of pressure 13 Outline • Tetracyclone • Retrosynthesis O OH O O • Alcohol Oxidation • Acyloin Condensation • Ylide • Benzoin O • Acyloin Condensation • Reflux • Recrystallization • Analyze Crude • Caclulate % yield • Get into pairs 14 14 Questions? 15