the microtcole loboratory 40-60 petroleum ether as the eluting solvent. Take about 6-mL fractions (12 fractions should he enough), and analyze the contents of each collection tube by TLC. Combine the contents of those tubes that contain the same isomer, and evaporate the solvents. The faster moving component is the cis isomer, which, when pure and free of solvent, can he crystallized by cooling, mp 44 OC;Qhe slower moving component is the trans isomer, mp 178 OC,fiwhich can he recrystallized from ethanol if necessary. The reaction usually gives comparable amounts of the two isomers.
Preparation of (E,E)-14-Diphenylbota diene
Place 380 mg henzyltriphenylphosphonium chlorides and 132 mg cinnamaldehyde into the tapered flask. Add 1 mL dicbloromethane, place the magnetic stirrer into the flask, and stir the mixture. Add 0.5 mL sodium hydroxide solution (8 g110 mL water), and stir the mixture at room temperature for 20 min. Transfer the contents of the flask into a 6-mL tube, wash the flask with 1 mL each of dichloromethane and water, mix the layers well, and separate them. Transfer the bottom layer (dichloromethane) into another tube, wash the aqueous layer with a further 0.5 mL of dichloromethane, dry the combined organic extracts with magnesium sulfate, filter the drying agent, and evaporate the solvent. Dissolve the residue in 0.7 mL ethanol with heating, cool it, and, when
crystallization is complete, filter the crystalline product on a Hirsch funnel, and wash it with 2 drops of ethanol. Recrystallize it from ethanol, and determine its melting point. Reported mp 149-151 "C. If desired, the E,Z-1.4-diphenylhutadienecan be isolated from the first ethanol mother liquor by evaporatingthe solvent and subjecting the residue to chromatographic separation. The E,Z isomer is an oil at room t e m ~ e r a t u r e . ~
'
Mayo D. W.; Pike R. M.: Butcher S. S. Micre scale Or~anlcLaboratory: Wiley: New Yo*. 1986: p 163. PikeR. M.; Mayo D. W.: Butcher S. S.: Butcher D. J.: Hinkle R. J. J. Chem. Educ. 1988, 83, 917918. MBrkl G.; Merz A. Synthesis 1973,295-297. 'Still W. C.: Kahn M.: Miba A. J. Org. Chem. 1978,43.2923-2925. me phosphonium salts are prepared by the Instructor by refluxing equimlar amounts of tri-
phenyi phosphine and the benzyl chlorides in chlcrofwrn for half an hour, cooling the solution, and precipitating the products with ether. The students could equally easily prepare them themselves. but we choose to do itmis way. Weis, C. D. Helv. Chtm. Acts 1968. 49, 234243.
Inert Atmosphere Techniques for the Microscale Laboratory Figure 1
Thomas A. Newton University of Southern Maine Partiand, ME 04103
An Apparatus tor Dispensing Alr-Sensltlve Liquids
Current microscale' and microlmacroscale- laboratory manuals offer ~ x p ~ r i m e n t u that require students to maintain anhydrous conditions, hut noneof them mcludes an experiment where working under an inert atmosphere is essentiaL3 One of the reasons for this, presumably, is the logistical difficulty of providing large numbers of students access t o inert a t m o s ~ h e r e s .We would like to describe a system'we have developed to introduce students to this aspect of modern chemistry. As part of a multistep synthesis af compound 1, a component of the aggregation pheromone of the male boll weevil, we have adapted a preparation4 of 3,3-dimethylcyelohexanone, as outlined in eq 1, to our mierascale laboratory. ~
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The synthesis requires students to generate lithium dimethylcuprate by the reaction of copper(1) iodide with methyl lithium. The figure illustrates our method for providing students with samples of methyl lithium and anhydrous ether. Obviously this device can be used for other reagents.
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the micro~ccrle Icrborcrtory
The sample dispenser consists of a 13- X 100-mm screw-capped culture tube fitted with a self-sealing, Teflon-lined septum and an open-topped cap. The liquid reagent is introduced via syringe into the culture tuhe after it has been flushed with argon. A small argon-filled halloon is used to maintain the inert atmosphere as students remove samples. (The inflated balloon is slipped over the end of a disposable 2.5-mL syringe body from which the ears have been removed.) The syringe is fitted with a 4-in. 22-gauge needle that extends to the bottom of the tube. The filled tube is then inverted and clamped to a ring stand. In this position the tip of the needle is above the surface of the liquid so that none of the sample enters the balloon. Students remove the &sensitive solution using polypropylenelpolyethylene syring~.~ When theexperimentisdoneon a 1-mmol scale, each student requires about 1.6 mL of 1.4 M methyl lithium. Since the capacity of a 13- X 100-mm culture tube is approximately 8 mL, each apparatus services four or five students. Four such assemblies meet the needs of an entire lab section. When used with a 31s-in., %gauge needle, a balloon/syringe assembly also provides students with a convenient means to maintain an inert atmosphere over their reactions. The argon-filled balloon allown students to flush the air from their apparatus through a vent needle. Without a vent, the balloon expands in response to addition of reagents to the apparatus. This prevents pressure from building up and facilitates the injection of samples. It should be noted that argon is preferable to nitrogen for two reasons. First, organolithium reagents do not react with argon. Second, being more dense than air, argon will displace it from the bottom of a reaction vessel.
Use an Eppendorf pipetter to dispense 1.00 i 0.02 mmol of 3-methyl-2-cyclohexen1-one into a dry 13- X 100-mm screwcapped culture tube. Stopper the tube with aTeflon-lined septum, and vent it witha 26gauge needle. Inject 2.2 0.1 mL of anbydrous ether into the tube. Remove the vent needle. Place 1.00 i 0.02 mmol of copper(1) iodide into a dry, 5-mL conical vial equipped with a spin vane. Seal the vial with a Teflonlined septum. Vent it as you did previously, and flush it with argon from a balloon attached to a 2.5-mL syringe fitted with a % in. %-gauge needle. After 1-2 min, inject 300400 wL of anhydrous ether. Remove the vent needle. Stir the CuIIether slurry in an ice-water bath rapidly for 3 4 minutes before injecting 2.20 i 0.02 mmal of 1.4 M methyl lithium into the reaction vial. Continue to stir the mixture for 5 min. With a 2.5-mL syringe, inject the 3-methyl-2-cyclobexen-1-one solution into the stirred CuIlether slurry over a period of several minutes. Continue to stir the mixture at 0 OC for 5 min and at room temperature for an additional 10 min. Using a Pasteur pipet, squirt the reaction mixture into 2 mL of NH3/NHaCI buffer (pH = 8-9) in a 25-mL Erlenmeyer flask. Swirl the solutions as you mix them. Continue mixing by drawing the sulution into the Pasteur pipet and expelling it back intn the flask several times. Hinae the mini-vial with another 0.5 mL portion of buffer, followed by 0.5 mL of solvent ether. Add these rinses to the Erlenmeyer flask. Transfer the entire sample to a 13- X 100-mm screw-capped culture tuhe. Stopper the tube tightly, and shake it vigorously. Centrifuge the sample for approximately 1min to facilitate separa-
*
tion of the aqueous and organic phases. Wash the ether layer with 1mL of saturated salt solution. Transfer the bulk of the ether layer into another culture tuhe containing approximately 300 mg of anhydrous sodium sulfate. Rinse the salt solution with 0.5 mL ofsolventether. Combine this rinse with the other ether layer. Cap the tube,and shake it gently. Filter the solution through approximately 100 mg of anhydrous sodium sulfate in a filter pipet. Rinse the culture tube with 0.5 mL of solvent ether, and pass the rinse through the filter pipet, too. Collect the filtrate in a tared 5-mL mini-vial. Evaporate the ether in a sand bath until the mass of the sample decreases by less than 5% between two successive weighings.
' a . Mayo. D. W.: Plke. R. M.: Butcher. S. S. Microscale Organic L a h t a y . 2nd ed.: Wiley: New York. 1989. b. Pavia, D. L.: Lampman, G. L.: Krlz. G. S.: Engel. R. G. lntrcduction to Organic L a h t a y Techniqw: A Microscale Appmach; Saunders: Philadelphia, 1990. a. Willlamson. K. L. Macmcale and Miw+ scab hgsnic Experiments; Heam: Lexington. 1989. b. Rodig, 0. R.; Bell, C. E., Jr.: Clark, A. K. Organic Chemishy Laboram Standardand Miscale Experimentsbunders: Philadelphia. 1990. An experiment h t requires Inert atmosphere ~ondltlonsappeared in J. Chem. Educ. 1990, 67, A232 while this work was In progress. House, H. 0.: Fischer. W. F.. Jr. J. Org. Cham. 1863, 33, 949. These syrlnges are available horn Aldrlch Chemical Co.. 940 W. St. Paul Ave.. Milwaukee. WI 53233. They are suitable for use with organ* llmlurn reagents.
A Simple Sublimation Apparatus Henry Brouwer Redeemer College Ancaster. ON L9G 3N0, Canada With the widespread use of small-scale reactions in organic chemistry, the role of sublimation as a means of purifying compounds is becoming more important. A recent article in this Journal1 described in allglass microsuhlimatar adapter for use witha 5-mL vial fitted with a 14/10 glass joint. To construct such a device would require glassblowing facilities and skills. Although a simpler sublimation apparatus can be made* by test tube with a ruhfitting a large side.her stopper bored to accept a smaller test tube, which serves as a cold-finger, such a device has several disadvantages. First, because the test tube needs to be small, it cannot contain murh ice. Second, it is located too high in the larger test tuhc for good sublimation. Third, it is difficult to bore the (Continued on page A641
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