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BRANDEIS UNIVERSITY CHEMISTRY 29A PRELAB WRITEUP AND EXPERIMENTAL REPORT SHEET NAME_ T.A.’S NAME DATE________ EXPERIMENT # __3_____ TITLE Tropilium iodide synthesis by triphenylmethyl carbocation intermediary Purpose: To synthesize Tropilum Iodide by reduction of triphenylmethanol and reaction with cycloheptatriene PRELIMINARY WRITEUP* (INCLUDING EQUATIONS, TABLE OF MATERIALS, THEIR AMOUNTS AND CONSTANTS. AND PRELAB QUESTIONS. Place these questions on the reverse of this page) (* use reverse of both sheets if necessary) Triphenylmethanol Fluoboric Acid diethyl ether Triphenylmethane Cycloheptatriene Methanol Hexane Triphenylmethyl Fluoborate Cycloheptatriene Tropilium fluoborate Tropilum iodide EXPERIMENTAL PROCEDURES* (include in preliminary writeup) 1. Mix 1.75mL cold acetic anhydride and 88 mg fluoboric acid, remain cooling on ice 2. add 195 mg triphenylmethanol through stirring, keeping solution cold 3. warm mixture until a homogeneous darkned mixture forms, do not heat for too long 4. add 78 mg cycloheptatriene, and allow the color change to occur 5. add 2mL diethyl ether, stir thoroughly, cool on ice 6. filter the solution through Hirsch funnel and collect both the filtrate and filtered solid 7. wash the filterate in 3M sodium hydroxide 8. then wash in 2mL water and then remove all traces of water with sodium sulfate 9. remove the solvent (ether should be only solvent left) and place in a tared reaction tube 10. measure crude melting point, and crude weight 11. recystallize with hexane and determine final melting point and weight 12. obtain weight of filtered crystals 13. take the filtered solid and dissolve it in hot water 14. place 0.25mL of NaI into solution then remove the solvent (vacuum filtration) 15. wash crystals in 0.5mL cold methanol 16. dry the crystals further 17. obtain weight of filtered crystals 18. place some crystals in 1-2 drops of water 19. drops 2% silver nitrate into solution until it turns clear MODIFICATIONS AND OBSERVATIONS* (Obtained from the lab experience.) The initial reaction with partner Ariel Levy did not work, the triphenymethanol (white irregular crystals), fluoboric acid (colorless liquid) and acetic anhydride (colorless liquid, smells like vinegar) solution mixed together and formed a yellow orange colored clear solution. After heating it darkened to a black/extremely dark orange color and did not react with cycloheptatriene, over time a black precipitate formed. In a group with Vimal we prepared the filtered solid preparation using 0.647 mL fluoroboric acid, 1.75mL acetic anhydride, 0.1048 g triphenylmethanol, and 79 mg cycloheptatriene (yellowish clear liquid). These formed a white precipitate before filtration. After filtration the weight of the filtered white crystals (small, granular)
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