edited by ARDEN P. ZIPP SUNY-Cartland
the microscale laboratory A Synthesis of 9-Fluorenol: Sodium Borohydride Reduction of 9-Fluorenone
c-1and,Ny13045
Literature Cited 1. Mayo.
D.W.; P ~ k e R. . M.: Butcher S. S. M , n n r . d e Orgnnir Lnhorninr:~,21E. Wilcy
,am
2. Mayo, D.W.: Pike. R. M.:Tiurnper P K . Micrnsm& O r ~ n ~ iLohoralo,:~, h. WE. Wiley
C. Susana Jones University of California. San Diego La Jolla, CA 92093-0303
The oxidation of 9-fluorenol by chromic acid-amberlite resin (I.2 ) is a common undereraduate exoeriment in mi., crosu:il(~ord;inic lal~oratones.The cost of the starring rnatt>rialii;louroximntelv .. " eleht rirnesrmentrr r h n n thnr ofthe product, 9-fluorenone. Thus, i t seemed worthwhile to investigate whether the reduction back to the alcohol was a reacGon that also could be carried out in the undergraduate laboratory. This new reaction, reduction of a ketone, could be assigned a s a special project to allow students in a second term of organic laboratory to gain experience with scaled-up reaction conditions. The product could be used for a class-wide microscale oxidation during the following semester. Students will be able to observe different percentage yield reactions. This borohydride reduction has a 95-100% yield, and the chromic acid-amberlite resin oxidation reaction has only up to a n 80% yield. Experimental Procedure For a microscale approach the chemicals in the next procedure may be reduced by a factor of 10. Caution Large scale preparation should be done in a hood because of the hydrogen gas evolved. A 5-g sample of 9-fluorenone is dissolved i n 30 mL of warm ethanol in a 100-mL beaker. To this solution is added, dropwise, 10 mL of a reducing reagent, freshly prepared, which consists of 200 mg sodium methoxide, 10 mL methanol, and 0.4 e sodium borohydride. This solution is allowed to stand undisturbed for 10-20 min. Acolor change is observed a s the reaction proceeds from the yellow 9-fluorenone to the white 9-fluorenol. The product i s precipitated by the addition of 50 mL of water and neutralized with 0.1 M HCI, vacuum filtered, and washed with cold water to remove any residual inorganic salt formed by the excess of the sodium horohvdride reaeent and hvdrochloric acid. The dried crude product is suffiyciently puEe for characterization bv meltine ~ o i n tinfrared . s ~ e c t r aand . NMR. The crude prdduct mek{ng pdint is 153 'c, with a product yield of 95-100%. Analytical Procedure Thin-layer chromatography (TLC) as indicated i n Mayo (1)could be used to monitor the progress of the reaction, the retention factor for 9-fluorenone is Rr = 0.80 and for fluorenol Rt = 0.56, obtained using Eastman Kodak flnorescent silica gel plates developed with 30% acetoneihexane as the chromatography eluent, and visualized under W light. Acknowledgment Support and suggestions from Barbara Sawrey improving this article are gratefully acknowledged. A252
Journal of Chemical Education
1994.
Microscale on a Budget R. Daniel Bishop, Jr. Colorado State University Fort Collins. CO 80523
The benefits to be obtained from converting an undera a d u a t e oreanic laboratorv o r o a a m to microscale exoeriLents havelbeen presented ion&cingly in several over the last few years ( 1 3 ) .One maior obstacle to makine the conversion, particularly for medium and large university programs, is the initial cost in new labware and eqnipment. In our program, there are 18 organic sections of 24 students each, so that complete conversion to microscale would require the purchase of 432 microscale lab kits. With even the least expensive kits retailing around $150 each, conversion costs could easily exceed $63,000. This challenge was confronted by selectively purchasing individual microware items, rather than complete kits, and incorporating inexpensive alternatives for items that could be omitted. The table itemizes both the labware omitted and the labware purchased for this conversion project. This approach, along with a manufacturer's discount, made the cost of glassware only $39 per drawer in 1990 when our conversion was made. (Today, the cost per drawer would come to about $58 before discount. All prices discussed in the remainder of this paper and i n the table are based on the 1994 undisconnted price list from Kontes.) Along with the glassware, 10 centrifuges, six digital 1.000mL microdisoensers. and 10 reaeent bottle-too. disoensers were purchased to equip our three labs for microscale work a t a total cost of $22.200. In addition. 72 aluminum heating blocks (one for each student station) were made by our machine shop. The microscale labware chosen was from the MicroFlex Kit line supplied by Kontes, designed for use with Kenneth Williamson's text, Macroscale a n d Microscale Organic Exoeriments (1989. D. C . Heath and Comoanv). However. " similar savings can be achieved with other manufacturers' labware bv selectine onlv " those items needed for the conversion. Our students are assigned locked drawers for their labware, which already included stainless steel spatulas, filter flasks. Hirsch funnels. and filter collars. so these items along with plastic storage cases were left off our shopping list for a savines of more than $41 Der drawer. The standari kit comes with twd 5-mL round-bottomed flasks, five calibrated reaction tubes (10 x 100 mm test tubes), and three 10-mL Erlenmeyer flasks . Each drawer was supplied with only one 5-mL RB flask, having selected the long-necked flask for its wider range of uses. Two reaction tubes and two 10-mL Erlenmeyer flasks were included. The three-armed connecting adapter, though useful, was felt to be redundant. Simple alternatives (see
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Conclusion below) can be employed in its place in most experiments that call for its use. These alterations to the order resulted By studying the equipment requirements for the experiin a n additional net savings of about $25 per drawer. ments used in an organic lab, improvising to design reaSeveral additional 13 x 100 mm test tubes, already in sonable and safe alternatives to published setups, and purstock, two 10-mL Griffin beakers, one side-arm test tube chasing only those individual microscale pieces actually (or "filter tube") and two 20-mm rubber septa were inneeded, it should he possible to outfit an undergraduate cluded in each drawer, a t a cost of about $10 per drawer. A organic labs with microscale equipment for less t h a n 5-mm hole was punched through one septum with a #5 $60.00 per student drawer. Although this still represents a cork borer to improvise a filter collar to fit into the sidesizeable cost, it is small enough to turn the shorter payarm test tube. This hole fits snugly around the microscale back period (from reduced chemical purchase and waste glassware, allowing the side-arm test tube to be attached disposal costs) into a convincing justification for making directly to the microscale distillation head for use as a disthe investment. tillation receiver. The side-arm test tube also can be used a s a reaction Acknowledgment vessel for gas generation, with the top sealed using the The author wishes to thank the College and University unpunched septum. Addition of reagent can be achieved Instructional Equipment Fund Committee a t Colorado using a syringe with needle inserted through the stopState for the grant used to pursue this project. per. If a n inert gas flow is required, the punched septum, fitted with a n appropriate piece of glass tubing (such a s Literature Cited t h a t from a medicine dropper) for connection to the gas 1. Butcher. S. s.: Mayo. D. w.: Pike. R. M ; Fmte. C. M: Hotham. J. R.: Page. D.S. J, line can be used to cap the side-arm test tube instead. Claarn. Edur 1985.62.147-El. 2. Harnrnond. C. N.;'hrnilling, M. J.J. Chmn Erlur 1987. 64. 440442. The standard microscale setup for a Fischer esterifica3. Zipp. A. P J Chenl. &uc. 1989.66.956-957. tion uses one arm of the three-arm adapter to trap water that has been removed from Microscale Savings Table the reaction mixture by co-distillation with toluene. The "h" shaped distillation head Item Omit Dollars nclude Dollars was used to accomplish this task, alleviating Saved Spent the need for the three-arm adapter. The di& 17.26 tillation head is oriented upside down to re- Plastic Case and Foam 6.03 semhle the letter " h and the air-cooled re- Column Chromatography Set-Up flux condenser (listed a s the "Distillation Chromatography Tip and Stopcock Column") is attached to its upward pointing 4.56 10 x 100 Calibrated Reaction Tubes arm. The arm directly below the reflux con2.87 10-mL Erlenmeyer Flasks denser serves as the water trap. This arm i s 14.73 sealed with a rubber septum, allowing one to 25-mL Filter Flask and Hirsch Funnel remove collected water with a syringe if nec- I-cc Syringe essary. The reaction flask is attached to the Stainless Steel Spatual 7.02 remaining downward pointing arm. R B flask, Short Neck 8.68 5-mL Another savings can be realized by substi5-mL R B Flask. Long Neck tuting 15-cm lengths of 11 mm (o.d.1 glass tubing with fire-polished ends for the glass 3-Arm Adapter 8.33 chromatography column that currently sells ~ i ~ ~ i~~~d l l ~ ~ i ~ ~ for $3.60. The plastic column tips can he pur- Distillation Column chased seuaratelv. T h e microscale thermometer 'dapter Ean serve as a connector Connecting Adaptersand Rod for this setup by attaching i t to the glass tub- Rubber Septa. Small, 8-mm ing and inserting the plastic column tip into ThermometerAdapter the adapter's smaller opening. Over $3.00 pE Tubing 2.13 are saved by this one substitution. Centrifuge Tube (15-mL) and Cap Most old two-finger clamps are too large 0.27 for the microscale setups, but the smaller P'Pet(l-mL) space hehind the clamp's bolt can he used to Stir Bars 1.95 clamp the Williamson kit microscale alumi- Filter Tube (Side-ArmTest Tube) num rod securely in place. By rotating the Beakers clamp 90 degrees and attaching the clamp to the stand, the o ~ e n i n abehind the bolt can Rubber Septa, Large accommodate the ho&ontally oriented alu$73.83 minum rod. The bolt can then he tightened to "NAdenotes Items not mciuded in the standard m~croscalek t prov~defirm support for the rod and its atXXX denotes (ternsalready stocked in student drawers tached glassware. Volume 71
Number 10 October 1994
A253
