A Laboratory Introduction to Polymeric Reagents In view of the widespread use of polymeric reagents in organic chemistry,' we felt an illustrative experiment would be useful to undergraduate chemistry majors. An "ideal" experiment would involve a recyclable polymer and inexpensive reagents, and would result in a crystalline product amenable t o recrystallization and successful use on a semi-micro scale. The following preparation, adapted from work by Cainelli, Cardillo, Orena, and S a n d ~ imeets , ~ these criteria. I t involves the oxidation of 9-fluorenol t o 9-fluorenone by use of a polymer-bound chromium trioxide reagent. Both the used polymer and the saturated Cr03 solution may he recycled polymer. The reaction's ease of warkup invites its use for micro-scale preparations, whose progress can be followed by TLC. Preparation of Polymer-Bound Cr03 10 g of Amherlyst A-26 resin (or 5 g of dry used resin) is stirred in 20 ml of saturated aqueous CIOB(caution-corrosive) for 30 min a t room temperature. The polymer is collected by suction filtration and washed with 100 ml of water followed by 20 ml of acetone. The polymer is then dried, either by allowing it to remain on the Biichner funnel under suction for 15-30 minor by allowing it to air-dry overnight. The yield is 5-6 g of dry oxidizing polymer.
Polymeric Oxidation of 9-Fluorenol A mixture of 1g (5.49 mmol) of 9-fluorenol (Aldrich), 5 g of the dry oxidizing polymer, and 35 ml of toluene is heated a t reflux with magnetic stirring for 1hr. If desired, the reaction's progress may be followed by thin-layer chromatography on fluorescent Silica Gel, developed using 30% acetone in heaane, and visualized by ultraviolet light. The polymer is removed by filtration, and the solvent is evaporated (either on a rotary evaporator or by warming while blowing a gentle stream of air over the surface). Reerystsllization from ethanol or ethanollwater affords pure 9-fluorenone, with typical student yields of about 0.8 g (4.4 mmal, 80%), and typical melting points of 81-86' (lit. 84-86').3
C. Accounts Chem. Research. 11.327 (1978): Hodee. P.. Chem. in Britain. 14.237 (1978) . C.. ,~~~~ Cainrlli, C.., Cardillo. G., Orena. M., and Snndri, s.; J. knwr ~ h o m 98.6737 11978, "THC Handbuok of Chemistry and Phyrrca," 38th Ed., p. C-308 (197111. 1. Reviews: .. ~. . T.emoff
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Colorado State University F o r t Collins. CO 80523
438 1 ~ournalofChemical Education
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L. G. Wade, Jr. Linda M. Stell
