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Synthesis of benzoin Renan Gongora Spring 2017
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Outline Tetracyclone Retrosynthesis Ylide Benzoin Reflux
Alcohol Oxidation Acyloin Condensation Ylide Benzoin Reflux Recrystallization Analyze Crude Caclulate % yield Get into pairs Outline 2
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X 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 Recall how low your yield was for the isopentyl acetate lab, this method could increase yield You’re not making this but you could X 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: /cr
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Retrosynthesis Imagine if you wanted to make this compound, how could I make it using simple/inexpensive materials? Ask yourself “a snapshot before it was this molecule, what was it?” How do I know how to make it? Analogy: Hedge Maze. create a map and then go through the maze.
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Synthesis: The next two weeks (separate lab reports)
HNO3 H2O/EtOH 1:3 v/v This week!!
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Synthesis GENERATE YLIDE in solution Add benzaldehyde H2O/EtOH 1:3 v/v
reflux 90 mins Enzymes vs Other Catalysts Lower energy of activation than ordinary catalysts Selective, “Lock and Key Model” Mild conditions Benefits of Enzymes May Avoid many side products May avoid dangerous/toxic chemicals
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Ylide Formation Resonance (S and N) stabilizes the ylide
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Synthesis 2M NaOH, 10 mins H2O/EtOH 1:3 v/v H2O/EtOH 1:3 v/v
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Procedure (1.5 g) (3.5 g) DI water (2 mL) 4.5 mL 2M NaOH
under ice bath 10 mins (NOT 2 days) DI water (2 mL) 15 mL EtOH Stirr until dissolved 100 mL RBF
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Recall Reflux Prevents solvent loss Prevents buildup of pressure
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Procedure (3.5 g) (4.5 mL) Heating Mantle place in reflux reflux
for 60 mins cool to r.t.
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Washing with cold DI water twice (20 mL)
Procedure Vacuum Filter Washing with cold DI water twice (20 mL) Weigh filter paper before this step What is in the flask? H3O+
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Procedure (3.5 g) just enough EtOH (8mL per 1g ) under ice bath
until crystals form just enough (8mL per 1g ) EtOH sit at r.t. MILDLY heat until completely dissolved 100 mL RBF
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Recrystallization Procedure
Weigh filter paper before this step Vacuum Filter Washing with cold EtOH (5 mL) What is in the flask? H3O+
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Outline Tetracyclone Retrosynthesis Ylide Benzoin Reflux
Alcohol Oxidation Acyloin Condensation Ylide Benzoin Reflux Recrystallization Analyze Crude Caclulate % yield Get into pairs Outline 15
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Questions?
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