An Easily Constructed Bicapped Tetrahedron Model Shuklchl Yamana Faculty of General Education, Kinki University, Kowakae, Higashi Osaka 577, Japan
A model of a b i c a ~ ~ etetrahedron d which is useful for teaching stereochemibiry (for example of t h e octadecarbonvlhexaosmium(0)J' can he made easily by using two sealed, empty envelopes. T h e principle of t h e m e t h o d is t o produce a t first, a model of twin tetrahedrons having a common line and t h a t of another t e t r a h e d r ~ n , ~aJn d next t o combine t h e m with each other t o yield t h e model given i n t h e title. T h e steps (illustrated in t h e figure) are given below. (11 Theenrelope is folded down the center lengthwise. (2) The right lower part oftheenwlopeis folded upat thecornerA
sothat theother corner Hfallaon thecentrrline.'l'his point on the line is marked C. (3) A horizontal line, perpendicular to the center line a t C is drawn. The intersection of this line and the left- or (right-) hand side of the envelope is marked D (or E). (4) The right lower part of the envelope is unfolded. On the reverse of the envelope, the point corresponding to the C is marked C*. (5) The lower part of the envelope is folded up along the line DE. On the original front of the envelope, the points corresponding to the A and B, are marked F and G, respectively. (6) The lower part of the envelope is unfolded. ( I ) The upper part of the envelope is cut off along the Line FG, and the remaining portion is folded hoth backward and forward along the lines AG, FB, and DE. (8) The top of the envelope is opened, and the left- and right-hand sidesaf the envelope are pushed together so that the two points D and E approach and touch each other hack to hack. (9) The top of the envelope is closed along the line FG and taped to produce a model of twin tetrahedrons having a common line. The triangles FC'C and C'AC are marked a and h, respectively.
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Journal of Chemical Education
Next, t h e second envelope of t h e same shape a n d magnitude as t h e first one usedabove, is employed t o produce a new tetrahedron model a s follows; (10) By the similar steps to (14) mentioned above, a horizontal line
D'E' is drawn along which the upper part of the envelope is cut off. On the reverse of the envelope, the point corresponding to the C'..~~~~~~~~~~~ is marked C'*. (11) The r~mainingmoiety is folded horh hackward and forward almg the line* A'? (i.e.. A'C'-I and C'B' (i.c., P H ' I . (12) The topoftheenvelope isopened and the twupoints Wand E' are forced to approach and meet to produce a new tetrahedron model. Two triangles B'C'T'and A'C'*C'are marked a'and h', respectively. (13) This new tetrahedron model is intruded on the two component tetrahedrons of the twin tetrahedrons obtained already by the steps (1-9), so that the faces a and a' (or h and h') touch together. In this case, each of the four corners B', C",C', and A' (of the new tetrahedron) and each of the other four comers F, C, C*, and A (of the twin tetrahedrons) are forced to approach and meet, respectively. The sides are taped to produce the model given in the title. ~~~
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Mason. R.; Thomas, K. M.: Mingos, D. M. P. J. Am. Chem. Soc. 1973,95.3802. Yamana, S. J. Chem. Educ. 1968,45245. 'Yamana. S.: Kawaguchi, M. Ann. Rep. Res. Sci. Educ., Kyoto Univ. Educ. 1979, 9. 25.
