JOURNAL OF CHEMICAL EDUCATION
REDUCTION OF BENZOPHENONE BY ALUMINUM ISOPROPOXIDE QUINTIN P. COLE Trinity CoUege, Hartford, Connedicut
tested a t five-minute intervals for the presence of a c e tone by treatment with a solution of 2,4dinitrophenylhydrazine. When a negative test was obtained the condenser was lowered t o effect total reflux. At fiveminute intervals the condenser was raised and a few drops of distillate collected and tested for acetone. The reaction was considered to be complete when this test was negative. The condenser was then raised and most of the I n the present work the student use of this proisopropanol distilled off. cedure on a much smaller scale (less than 0.01 mol) Twenty milliliters of 2-N was found to be practical, employing the simple appahydrochloric acid was ratus pictured in the figure. The finger condenser a, stirred into the residue and the 25 ml. distillation tube b, and the water bath c were the crystalline benzohystandard pieces of apparatus commercially a ~ a i l a b l e . ~ drol filtered off, washed The air condenser d was a piece of 12 mm. glass tubing with dilute acid and water, and the receiver e was a small test tube. The students and dried in the air. It were supplied with a I-M solution of aluminum isoprowas purified by crystalpoxide in isopropanol prepared by the procedure delization from benzenescribed by Adams and used without purification. The petroleum ether. T h e tendency of the aluminum isopropoxide to deposit as average student yield of d crystals from this solution made it advisable to arrange purified product was 75 for use of the reagent within a few days of its prepaper cent of the theoretical. ration. - It was found that conTen milliliters of the aluminum isopropoxide solutinuous distillation for tion, 1.5 g. (0.008 mol) of benzophenone, and some boilabout one hour was necesing chips were placed in the distillation tube. The sary to obtain the first mixture was heated on the water bath and the rate of negative test. Hence, testdistillation adjusted to one or two drops per minute by ing of the distillate may raising and lowering the condenser. After thirty properly be deferred that minutes of continuous distillation the distillate was long. A t o t a l heating ~. ----~ -----. -. --. . --.--.. . -. . -. . . -... .. . . . -. period of 1 X t o 2% hours ~. . . -------. ---. -. ' Annans, R., "Organic Reactions," John Wiley & Sons, Inc., .-.-. -----------. . --------------was required for complete New York, 1944, Vol. 11,pp. 198-203. Wilkens-Anderson Company, Chicago, Illinois. ~ . d ~ =At Pi ~~. ,~ . ~ ~ reaction. The Meerwein-Ponndorf-Verley reduction of benzophenone by aluminum isopropoxide and isopropanol is reported' to give a nearly quantitative yield of benzohydro1 when a reasonably efficient fractional distillation assembly is used to remove the acetone formed and the quantity of benzophenone reduced is 0.1 mol.
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