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17 Cards in this Set
- Front
- Back
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Cycloaddition |
Reaction in which two unsaturated molecules react to form a ring |
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Cycloaddition of Dienes and Alkenes |
Forms cyclohexanes, discovered by Otto Diels and Kurt Alder |
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Importance of Diels-Alder Reaction |
Allows for the production of functionalized six-membered rings, which are very important especially in pharmaceuticals |
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Diels-Alderase |
Enzyme that can catalyze a diels alder cycloaddition, found in nature |
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Best Diels Alder Reactions |
Works best with dienophiles that contain an electron withdrawing group directly attached to the alkene The more electron-deficient the alkene, the more reactive it is |
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Type of Reaction |
Concerted: bond breaking and bond forming occur simultaneously Stereospecific: reagent dictates product (cis reagent = cis product) |
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Cheletropic Elimination |
Produce s-cis-1,3-butadiene (gas at room temp) from 3-sulfolene with heat |
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Overall Reaction |
1. 3-Sulfolene and heat produce s-cis-1,3-butadiene 2. s-cis-1,3-butadiene + maleic anhydride (in xylenes) produces 4-cyclohexene-cis-1,2-dicarboxylic anhydride |
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Procedure |
1. Add 1.5 g maleic anhydride, 2.7 g butadiene sulfone, a stir bar, and 4 mL of xylenes to a 50 mL RB flask 2. Reflux (55%) for 30 minutes with hood closed (so SO2 gas doesn't escape) 3. Let reaction cool, add 9 mL of xylenes, heat until warm then decant into 50 mL beaker 4. Add warm petroleum ether (~ 5 mL) until precipitate forms and chill in ice bath (5 min) 5. Filter with Buchner funnel washing with cold petroleum ether |
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Waste Disposal |
Filtrate: "Diels Alder Waste" container Rinse everything with acetone |
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3-Sulfolene |
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s-cis-1,3-butadiene |
Plus SO2 gas |
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Maleic Anhydride |
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4-cyclohexene-cis-1 2-dicarboxylic anhydride (Diels Alder Product) |
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Hazards |
Maleic Anhydride: corrosive, causes burns to skin & eyes and allergic reaction/irritation Butadiene Sulfone: corrosive, causes burns to skin & eyes, respiratory irritant, foul smell Petroleum ether: toxic & flammable (bp 36-50 C) Xylenes: toxic & flammable (bp 141-143 C) Sulfur Dioxide: toxic, foul smelling |
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Diels Alder Reaction Overview |
Initiated by heat, thermal reaction Forms 6 membered rings by breaking 3 pi bonds and creating 2 sigma bonds and 1 pi bond |
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Diene and Dienophile Reactivity |
Can only react in cis form Electron withdrawing groups make dienophile a better electrophile |
