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C H E M I C A L PROJECTS
The Formation of Acetone from Acetates See NOYCE,W. K., J. Chem. Edue., 26, 275-6 (1949).
Many metal acetates decompose when heated, forming acetone as one of the major products. Probably, if the heating is prolonged or if too high a temperature is reached, some of the acetone which is originally farmed pyrolyzes (decomposes by heat); and other products are thereby ohtained. The other products may also be formed directly in the initial heating of the metal acetates. The procedure is simple. A hydrated or anhydrous metal acetate or a mixture of metal acetates is heated in a test tube and the volatile decomposition products are condensed in a water-cooled condenser, collected, and examined. The yields of acetone obtained vary considerably depending upon conditions which have not been identified, according to the author.
Questions:
Select two or more metal acetates and show that acetone is formed when each of the selected acetates is heated. What other products are also formed in the pyrolysis of metal acetates? Account for their formation, and devise procedures which will verify your explanation. What factors, for any single metal acetate, affect the yield of acetone or other products obtained? Can you explain why the identified factors affect the yield? Test your explanations by further laboratory work. Is i t true that mixtures of more than one metal acetate give a higher yield of acetone than either of the two singly? Account for the results you obtain, and test your explanations.
The Preparation of Nitrosobenzene See ROBERT~ON, P. S.
AND
VACGHAN, J., J. C h m . Educ., 27,605 I:l950).
I n many organic syntheses i t is necessary to separate the desired product from a mixture of side-products and residual reagents. The over-all yield of a synthetic process is often adversely affected by this necessary f i n d separation, since the separation itself may involve some mechanical or chemical loss of the desired material. Usually, several separation procedures w e feasible; and the selection of an optimum procedure is an interesting challenge, frequently requiring evaluation of several possible pbcedurew by laboratory investigation. As a. specific example, nitrosobenzene (C.HENO), can he pre~ m from d nitrobenzene (CnHSNO2)by treatment with zinc ;n' aqueous ammonium chlbride solution followed by oxidation of the intermediate, phenylhydroxylamine (CsHrNHOH), with
potassium dichromate. The nitrosobenzene is finally separated, in the usual procedure, by steam dirtillation. Robertson and Vaughan point out that i t can also be separated by distillation a t about 65°C under 17 mm pressure. The final yield is slightly greater although more t,ime is required for the vacuum distillation.
- ......... Select some other organic synthetic process; devise two or more procedures for the separation of the final product. Which procedure is best? Or, see if you e m improve upon the s e p m tion procedures which have been recommended by other workers.
Laboratory Experiments Dealing with the Manufacture of Paints See BOIG,F. S., J . C h a . Educ., 2 4 , 5 9 4 4 and 599 (1947). Mr. Joseph H. Rohloff, Warwick Veterans Memorial High School, Warwick, R.I., made valuable suggestions. In this article, Boig describes the stpps in the preparation of several different paints, from the precipitation of the pigment to the final product. Recipes for blue, green, and red paint are given in detail. Questions:
Basing your work on the principles discussed in the article, prepare a paint of some other color, using mixtures of two or more pigments. All of the paints described by Boig use linseed oil as the vehicle. Are any other vehicles also suitable? If so, what are their advantages and disadvantages, compared to linseed oil? Several other different substances, in addition to those men-
tioned by Boig, are used as pigments in commercially available paints. Prepare one of these pigments and use it in the formulation of a paint. Is there a relationship between the opacity of a paint and the difference in refractive index hetween pigment and hardened vehicle? List the qualities that are desirable in s. paint. (These will differ, depending upon the use to which the paint is to be put.) Modify the recipes given by Boig, or establish your own recipe and modify it. Determine the effect of the modifications upon the qualities of the paints you prepare. Account for these effects and test your explanations by further laboratory work. Since 1947 many new types of paint have been devised and are now available. Select one of these types and, following the general principles discussed in the article, prepare a small quantity of such paint.
