less expensive than PFD (bp 142 "C) are also a t least a s volatile a s PFDMCH (bp 101-102 "C). I n sum, perfluorodecalin is a suitable bubbler fluid for measuring small flow rates of Clz, SOz, or HC1. We would expect it to be usable with other gases of similar reactivity toward alkenes; Clz, HC1, and SOz react with alkenes by three different mechanism^,^ and thus represent three distinct classes of gases for which PFD bubblers will be useful. Acknowledgment We thank J.C. Baum of this department for loans of h hardwareandC.H. Vanselow I ~ n i v e r s iot f~~ o r t Carolina a t Greensboro~for helpful discussions. This work was supported by the ~ l o r i d aInstitute of Technology ~ e s e a & h OEce. and bv the donors of The Petroleum Research Fund, admidistered by the American Chemical Society.
Synthesis of trans-2-tert-Butylcyclohexanol via Hvdroboration: A Microscale Oraanic Exoeriment Demonstrating Syn idi it ion ' Carl T. wigal,' William T. Hopkins, and Bruce P. Ronald Idaho State University Pocatello, ID 83209 The hvdmboration reaction. first reported bv H.C. Brown in i956 (I), is a classic example i f regio&emical and stereochemical control. The addition of borane to a n alkene produces an organoborane that upon oxidation with basic hvdroeen oeroxide results in svn addition of water in an a n t i - ~ a r k o v n i k o v fashion: While t h i s reaction demonstrates imvortant mechanistic aspects of alkene hydration, the stereochemical consequen&s have been difficult, ifnot impossible, to prove in a typical organic teaching laboratory. Previously reported hydroboration experiments (2-5)have failed to address these mechanistic issues or
required the preparation of derivatives to determine the relative stereochemistry of the addition. We have developed a microscale experiment, the hydroboration of l-tertbutylcyclohexene, which d e m o n s t r a t e s both t h e reniochemical a n d stereochemical outcome of t h e hy&oboration reaction via a melting point and a Jones oxidation test. This reaction is auite simple in both procedure and equipment needed yet demonstrates uneqtuvocally themechanist~caspcctsofthehydrohoration reaction. Experimental All reagents used in this experiment are available from Aldrich Chemical Company Inc. and were used without further purification. 4C12and HCl: Streitwieser, A,, Jr.; Heathcock, C.H. Introduction to OrganicChemistry,3rd ed.; Macmillan:New York, 1985;pp 255-262. SO,: Rogid. M.M; Masiiamani, D. J. Am. Chem. Soc. 1977, 99, 5219-5220.
I n a 10-mL round bottom flaskz equipped with a CaClz dryingtube, magnetic spin vain, and aircondenser is added 1-tert-butvlcvclohexene (0.366 mL. 2 mmoli. Added slowlv to the flack \;ia syringe is 1.0 M B H ~ T H F( 2 0 mL, 2 mmolj. After addition of the BH.-THF. the reaction mixture is allowed tn stirat room trm;eraturefor 1 h Added dropwise to the rpactlon mixture wh~lestirnneis 3M NaOH 110 m1.1 followed by 30% hydrogen peroxide'il.O mL). Caution: 30% KOzcan cause blistering of the skin! While being stirred, the mixture is heated for 45 min a t reflux using a hot water bath and then is transferred to a glass centrifuge tube allowing the mixture to cool to mom temperature. The reaction mixture is extracted with dichloromethane (3 x 1.0 mL). The combined organic phase is washed once with water (1.0 mL), dried over anhydrous NazSOa for 10 min, and transferred to a tarred vial for solvent removal under a stream of' nitrogen. The white crystalline pn~ductis we~ghedand the melting point detrrmined. Asmall sample is used fur a Jonenox~dationtest 31. Discussion We have found this exveriment to be a valuable addition to our laboratory curricuium. Atypical student yield of this reaction is -75 % with exclusive formation of the trans isomer a s determined by gas c h r o m a t o g ~ a p h ~ T .h~e regiochemistry of the addition is determined by the Jones oxidation test. The Jones oxidation test, in this case, differentiates a secondary alcohol (anti-Markovnikov addition) *om a tertiary alcohol (Markovnikov addition). Therefore, 2-tert-butylcyclohexanolsgive a positive Jones test while 1-tert-hutylcyclohexanolgives a negative Jones test. The stereochemistry is determined by the melting point. The trans isomer has a meltina point of 84-85 "C (6)while the cis isomer melts at 66-57 ' F ( 7 , .A typical melting range of thenudealn,holforstudents was76-81 'C . Subhnination of the crude alcohol can be carried out in a beaker or test tube by heatinp the material on a 80 "C sand bath for 5-10 min rcsultinl: k formation of long needle-like crystals on the walls of the container. Melting- range of the sublimined crystals was 82-84 "C. Acknowledgment We would like to acknowledge the participation of the students of CHM 304 a t Idaho State University for their assistance in developing this experiment. Literature Cited . . . . 3. Mayo, D. W.:Pike,R.M.; ~uteher,S.S. ~ i m s m O~ganie k Lobomion; Wllw: New York,1989. 4. Goach, E. E. J. Chm. Edur. 1990,67, A232. 6. Picketing,M. J Cham.Educ. 1990.67, 436. 6 Milstein, 6I3A 126. 7. Beilsleix, 6131, 125.
'Author to whom correspondence should be addressed. 2Thissynthesiscan also be carried out on a 112 scale to accommodate a 5-mL conical vial. =GCanaivsis 110%Carbowax. 2 m x 1/8". 120 OC. He 50 mL/min.\ of the comherial mixture of isomers gave the following retentioi times: cis isomer, 9.02 min.: trans isomer, 9.98 min. Volume 68 Number 12 December 1991
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