Mel Gorman, Dennis DeMoWia, Daniel Doonan, and Gary McDonald
Un~vers~ty of Son Franc~sco 94117 Son Fronc~sco,Col~forn~a
A
h0rganiC Synthesis in Undergraduate Research
sampling of appropriate entries in the calculated directly; the dioxane content was obtained yearly indexes of the JOURNAL OF CHEMICAL EDUCATION by difference. and a compilation of undergraduate research' reveal Determination of the number of moles of dioxane per mole of lithium thiocyanate in duplicate determinations that inorganic synthesis occupies a minor role in undergraduate research. We have found that a series of of four separate preparations gave 0.98, 1.02, 1.05, 1.08; i.e., LiSCN.C4&02 yield: 92%. The product related inorganic syntheses has the advantages of (a) is unstable, yielding dioxane very rapidly a t 20°C, and having a reasonable chance of success, for student the resulting lithium thiocyanate is extremely hymorale, (b) allowing the student to proceed with maxigroscopic. mum independence, and (c) letting him see that he is Reagent grade sodium thiocyanate was dried for 24 part of an integrated program. This project stemmed from student work on 1,4-dioxane as an a d d u ~ t , ~ hr at 130". One gram of the anhydrous salt was added to a mixture of 15 ml of absolute ethanol and 25 ml of which was then applied to inorganic thiocyanates. purified dioxane. When the ingredients were boiled the Preparation of the dioxanates of the alkali thiocyanates has been a continuing theme of research by undersalt dissolved and after 30 min refluxing the reaction graduates. Their collaborative procedures for synvessel was cooled at 0" for 2 hr. The resulting white flaky crystals were collected and analyzed as described thesizing these new compounds are described below. above. The number of moles of dioxane per mole of Anhydrous lithium thiocyanate was prepared by the sodium thiocyanate in duplicate runs of three separate method of Lee.3 One-half gram of the salt was dispreparations were 3.01, 3.04, and 3.06; i.e., NaSCN, solved in 10 ml dry ether, and the solution was added to 5 ml of purified dioxane. White fluffy crystals 3C4H802. Yield: 93%. The product is of the same order of stability as the lithium compound. formed instantly. They were collected by suction Reagent grade potassium thiocyanate was rethrough a 35-mm diameter coarse sintered glass filter crystallized from water and dried 24 hr at 120'. One and washed quickly and thoroughly with 5 ml cold gram of the anhydrous salt was refluxed with 20 ml of (0") dry ether from a 10-ml hypodermic syringe. This dioxane and 10 ml of ethanol. After the salt was disoperation was completed in less than 30 sec. The small solved completely (in about 1 hr) the reaction vessel amount of adhering ether was allowed to evaporate was stoppered and stored at lO0C for 24 hr. Oblong, until its odor disappeared (about 1 min). The crystals translucent crystals separated, and were collected and were transferred quickly to a weighed, screw-cap, analyzed as described above. The number of moles of 50-ml volumetric flask. After reweighing and disdioxane per mole of potassium thiocyanate in duplicate solving to volume, 10 ml aliquots were run through a runs of four separate syntheses were 1.94, 1.98, 2.01, column (0.6 cm X 13 cm) packed with the acidic form and 2.09; i.e.; ICXN.2CaH802. Yield: 84%. The of the cation exchange resin Amberlite IR-120 at the product is of the same order of stability as the lithium rate of 1 ml/min and eluted with 75 ml of water at the and sodium dioxanates. same rate. The eluted acid was titrated with standard The above procedures were adopted after various sodium hydroxide and the lithium thiocyanate content unsuccessful methods were tried. No single set of operations could be found for the preparation of these three dioxanates. In general, due to the hygroscop'FINLEY,K. J., AND HAYLLES, W. J., "Directory of Undergrsntusta Research," Department of Chemistry, Rochester icity of the alkali thiocyanates and the instability of the Institute of Technology, Rochester, N. Y., 1965, p. 11-15, dioxanates, the amount of water in the reagents had to 35-6. be kept to a minimum. The dioxanates are stable in 3 GEUEN, T., AND GORMAN, M., J. Inorg. N w 2 Chem., 27, contact with suitable concentrations of dioxane a t low 482 (1965). "LEE, D., Inmg. Chem., 3, 289 (1964). temperatures (@lo0). But a t 20°C in the atmosphere
466 / Journal o f Chemical Educafion
vapors of dioxane are given off rapidly, so that success in analysis a t room temperature depends on rapid handling of the solids. Attempts to prepare the corresponding rubidium and cesium compounds by these procedures were unsuccessful. To a seasoned investigator, the mere synthesis of a new compound without further investigation of its structure, thermodynamic properties, use as an intermediate, etc., would indeed be quite trivial, but to the embryo chemist, the knowledge that he has made a compound never before prepared gives a tremendous lift to his scientific ego. I n our case it was especially satisfying to learn that undergraduates were successful in one instance where experienced investigators partially failed.' Even those students who worked without success as far as preparing a new compound was concerned nevertheless felt vindicated with a sense of accomplishment, because they knew they were participating in a systematic and joint project with their
fellow students. Undergraduate students are now attempting to synthesize the dioxanates of the alkaline earth metal thiocyanates. No claim is implied that the synthetic problems presented here are in any way unique or unusual; all we say is that they are well adapted for undergraduate research goals. It is always beneficial to the morale of the undergraduate researchers to learn that their type of work is novel and important enough to engage the current attention of workers in the field. A case in point is the recent discovery and use of macrocyclic polyether complexes with alkali metal ions.5
' TRONOV,B. V., ZHELNOV,A. A,, AND GAVRILIN,G. F.,Org. Kompleks. Soedin. Tomsk., Tomsk. Univ., 1965, 151; Ref. Zh. Khim., 1966, Pt. 1, Abstract no. 17V51; Chem. Abstr., 66, 61386q (1967), were unable to prepare the sodium thiocyanate dioxamte directJy from its components. However, they did make it indirectly. C h m . Eng. News, 48, no. 9,26 (1970).
Volume 47, Number 6, June 1970
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