C. W. Schimelpfenig
The George Washington University Washington 6, D. C.
I
Laboratory Synthesis of a Heterocyclic Compound
The preparation and reactions of heterocycles are often neglected in the course in general organic chemistry. That time is a major factor in determining which topics to omit can hardly be debated. However, lack of time in the laboratory need not be a resson for missing the opportunity to give students practical experience with heterocyclic compounds if rather short experiments can be developed. Short preparations of r-caprolactam, fluorescein, and cyclic anhydrides and imides may be foupd in a number of laboratory manuals; excellent longer experiments are included in the laboratory manuals of Mackenzie' and of Robert~on.~ Mackende's preparation of phenylmethylpyrazolone requires two and one-half hours and his preparation of hydantoin requires two hours. Robertson's preparation of quiuoline requires eight to ten hours. We have developed a test tube experiment which requires approximately 45 minutes and which, moreover, serves to introduce to the student a valuahle research technique. Because of the proximity of the melting points of o-nitroaniline and of benzofurazan oxide, the fact that both contain the same elements, and MACBENZIE,C. A., '%xperimental Organic Chemistry," PrenticeHall, Inc., Edgewood Cliffs, N. J., 1955, pp. 175, 176. ROBERTSON, G. R., "Laboratory Practice of Organic Chemistry," 3rd ed., The Macmillan Co., New York, 1954,p 330.
their similarity in color (orange and yellow), it bccomes feasible to demonstrate non-identity of starting material and product by mixture melting point. The procedure for the preparation of benzofurazan oxide is an adaptation of the method of Mallory.3 Preparation of Benzofumzan Ozide. Add to 15 ml of a 10yo solution of potassium hydroxide in ethanol contained in a 25- X 2W-mm test tube one gram of o-nitroaniline. Warm the mixture slightly until the solid dissolves. While swirling the solution, add dropwise a. commercial bleaching solution until precipitation is complete (about 30 ml of "Chlorox" is necessary, for example). Remove the yellow crystalls by motion filtration. Dissolve the moist solid in 10 ml of ethanol, filter if the solution is turbid, and add 20 ml of water dropwise. Remove the d i d by filtration and allow the crystals to dry overnight. Determine the melting paint and percentage yield of the product. Observe the melting behavior of a mixture af the product and o-nitroaniline.
I n a typical performance the melting point of the o-nitroaniline (Eastman product, not recrystallized) was 69.5-7l0, the melting point of the benzofurazan oxide was 66-67.5O0, the melting range of a 50:50 (weight) mixture of the starting material and product was 38-61", and the yield was 40%. More of the product could be recovered from the ethanol-water filtrate. if desired. MALLORY, F. B., in "Organic Syntheses," Vol. 37, edited by J. C ~ S O N John , Wiley & Sons, Ino., New York, 1957,p. 1.
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Journal of Chemical Education
