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2311 lec 8 - • Aldol Condensation Rx Aldol • Two...

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Unformatted text preview: • Aldol Condensation Rx Aldol • Two Synthetic Routes Two of Preparation Tetraphenylcyclopentadienone Tetraphenylcyclopentadienone O Ph Ph Ph Ph • Diene for next reaction Diene • Highly conjugated, all Highly sp2 carbons, carbons, • Purplish/black Purplish/black Reaction Scheme Reaction O Ph Ph + O Ph O Ph O OH solvent Ph Ph Ph + 2 H2O dibenzyl ketone (1,3-diphenylacetone) benzil KOH Ethanol Ph Reaction A Refluxing ethanol 30 minutes Reaction B Triton B triethylene glycol 100 oC, 5 minutes Reaction Conditions B Reaction Mechanism of Aldol Condensation Reaction Mechanism of Aldol Overall Reaction O Ph 1 2 3 Ph + O 4 Ph 5 Ph O O OH Ph 1 2 3 Ph + solvent Ph 2 H2 O 45 Ph Formation of Nucleophile (resonance stabilized anion) O Ph H Ph H + OH Ph H O Ph Ph enolate anion O Ph plus resonance with phenyl ring pKa = 15-16 Mechanism, Continued Mechanism, O Ph Ph Ph Ph Ph δ+ O O new carbon-carbon bond formed O H Ph O Ph Ph H-OR Ph O OH H Ph OH Ph Ph Electrophile O O heat (base-catalyzed dehydration) O Ph Ph repeat steps Ph Ph Ph Ph O O Ph Ph Goals Goals • Isolate crystals from BOTH reaction Isolate conditions • Compare yield and quality of crystals Compare • Which reaction would you scale to 1 kg ! Which • Use TPCPD in Diels-Alder reaction Use Computational Chemistry Model of Computational Tetraphenylcyclopentadienone What is Green Chemistry? What • When the EPA began its research grant When program in 1991, it defined green chemistry as.. “Innovative Chemical Technologies that reduce or eliminate the use or generation of hazardous substances in the design, manufacture and use chemical products” What is Green Chemistry? What • Use chemistry to PREVENT pollution Use • Design processes that lower or eliminate Design the use of hazardous chemicals • Meet current needs for chemical products Meet without jeopardizing future needs • Focus on renewable resources (raw Focus materials from plants, other sources besides petroleum) 12 Principles of Green Chemistry 12 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Prevention waste (rather than treat) Prevention Atom Economy (max atoms used for product) Less Hazardous Chemical Syntheses Designing Safer Chemicals Safer Solvents and Auxiliaries (separations) Design for Energy Efficiency (rt and atm pressure) Use of Renewable raw materierals and feedstocks Reduce Derivatives (protecting groups) Use Catalytic reagents when possible Design for Degradation in the environment Real-time Analysis for Pollution Prevention Inherently Safer Chemistry for Accident Prevention Atom Economy Atom Mohrig – pp. 20-21 Mohrig Manual – pp. 112-113 • The atom economy for a reaction can be The calculated using the following equation: Molecular weight of desired product Molecular weights of all reactants Percent atom economy = x 100% • Consider Aldol Condensation reaction Consider Reaction Efficiency Reaction • p. 21 Mohrig p. • Hydrogenation Rxn - Assume yield of 85% Hydrogenation ...
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