Oxidation of Alcohols Using Calcium Hypochlorite and Solid/Liquid Phase-Transfer Catalysis Oxidation of alcohols to aldehydes and ketones is a fairly common exercise in elementary organic chemistry laboratories. For many years, the oxidizing agent of choice was acidic dichromate solutions, but concerns about toxicity and waste disposal have led t o use of hvoochlorite solutions as alternative oxidizing media.',2 The orevious articles both report the use of "awimminn oonl ehl~~ine." ~ a e renort h considers oxidation of only . .. ~. an aoueous solution of 12-15% sodium hvuochlorite. one compuund, cyclohrvanol to ryclohpxane' and 2-pn,p;mol 11, acetoneL \Vr haw drwluped n simpler alternative and generaleed the pmwrdurr U, include synthesis uian aldehyde frvm d primrig. nlrcrhol a%well as several ketones i r m s r c m d a g alcohols. Solid calcium hypochlorite (65% available chlorine) from a local swimming pool supplier was used as the oxidizing medium.3The alcohol was dissolved in dichloromethane as a solvent. Tetrahutylammonium hydrogen sulfate was employed as a phase-transfer catalyst to transport the hypochlorite ions from the solid to the liquid phase. Solid calcium hypochlorite has the significant advantages of being relatively stable and easily stored as compared to the various hypochlorite solutions. Also, "liquid swimming pool bleach" requires that large volumes of solution he used.' The following conversions were carried out: (1) henzyl alcohol to benzaldehyde, (2) 2-hutanol to 2-hutanone, (3) 1phenylethanol to acetophenone, and (4) cyclahexanal t o eyclohexanone. Gas chromatographic and infrared analyses of the reaction mixtures showed greater than 99% conversion in each case. Control reactions without the catalyst showed little conversion over the same period. Actual student yields ranged from 5&91% (59-7890 for benzaldehyde, 63-87% for 2-butanone, 58-72% for acetophenone, and 7&91% for cyclohexanone). Following is a typical procedure. Other procedures are identical except for the amount of alcohol and temperature range for product collection. ~~
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Procedure CAUTION: Cany out the procedure in a hood or well-ventilated room t o avoid exposure to,any chlorine that might he released. Be sure to mix the alcohol with the solvent before adding it t o the hypoehlorite; reaction with undiluted alcohol can he violently exothermic. Place 32.8 g (0.15 mol) of the calcium hypochlorite in a 500-mL Erlenmeyer flask. Mix 12 mL (0.1 moll of 1-phenylethanol and 150 mL of dichloromethane and add to the bleach. Next add 1.7 g (0.005 mol) of tetrahutylammonium hydrogen sulfate and a few drops of water. Fit the flask with a reflux condenser and stir a t reflux temperature on a magnetic stirrerhot plate5 Reaction was determined by GC analysis t o be complete in 1h. The reaction mixture was decanted into a clean flask, 2-3 small crystals of sodium hydrogen sulfite were added and the mixture swirled for about 5 min to decompose any hypochlorite oresent (anlv traces. a t most. are carried over). then filtered t o remove any solids. After drying over a small amount of an~vrlronr'aod~nm sulfate. the diehloromethanekas removed hv distillation. The oroduct aietiohenone was collected over ~~, thr range 197.21%) Y'.Yield was 7.0 g (38rr,. The solid r~sidue,which contains unreacted calcium h y p ~ ~ c h l ~ rran ~ t ebe , ~ hydroyrn suliatr in 100 mL or *,of watrr.Thrrxneutraltwd by addition oldsolution made by d ~ s d v i n 5c . 2 olsvdium periment is easily completed by mast students in a 3-h laboratory period. ~
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EDW;.. 58,824 (1981). See also references therein. Zuezek. N. M.. and Funh. P. S.. J. CHEM. 2Kauflman,J. M.,and McKee, J. R., J. CKM.E m . , 59, 862 (1982). A more expensive product, available from Aldrich Chemical Co., P.O. Box 355, Milwaukee, WI 53201, stock no. 21,138-9, gave similar resuns. 'The auihors cited above used 75 mL and 312 mL, respectively. The reaction e m be accomplished without magnetic stirring (see footnota 2). but it is not as convenient.
John W. HIII, Jeffrey A. Jenson, Charles F. Henke, Joseph G. Yaritz, and Richard L. Pedersen University of Wisconsin-River Falls River Falls. WI 54022
1118
Journal of Chemical Education
