An Easily Constructed Tricapped Trigonal Prism Model Shukichi Yamana Department of Kyoushoku Educatlon, Kinki University. Kowakae, Hlgashl Osaka 577, Japan
A model of a tricapped trigonal prism that is useful for teaching stereochemistry (for example, of neodymium bra. mate enneahydrate, Nd(BrO&.SH20)' can be made easily by using two sealed, empty envelopes. The principle of the method is to produce a t first, a model of twin tetrahedral pyramids having a Common line (laheled Model 1) and that of monocapped trigonal prism (labeled Model 11) and next to combine them with each other to yield the model given in the title. The stens in the figure) . (illustrated . - are -given below. (1) The fiat figure shows the starting configuration,which is produced by steps 1-3 of the previously published a~ticle.~ (2) The lower part of the envelope is folded up at D so that the pointE falls on thecenter line (C).The point corresponding to E is marked F. (3) The lower part of the envelope is unfolded. (4) A horizontal line, perpendicular to the line (C) at F,is drawn so that it crosses the left- and rixht-hand sides of the envelope at C andH, respectively. (5) The lower part of the envelope is folded up along the line GH. The points corresponding to D and E, are marked I and J, respectively.
640
Journal of Chemical Education
(6) The lower part of the envelope is unfolded.
(7) The lower part of the envelope is folded up so that lines FH and FC lie just an lines (C) and FC, respectively. On the obverse of the envelope, the points correspondingto E and D, are marked
K and L, respectively. (8)The lower part of the envelope is unfolded, (9) The middle points of the lines KI and LD are marked MandN, respectively. (10) A line is drawn from the Kso that it is parallel with the line LF. The intersection of this line and the line MF is marked 0. (11) A line is drawn from the 0 so that it is parallelwith the line (D). The intersection of this line and the line NF is marked P. (12) On the line (Dl a point is marked Q so that the lengths of the lines IQ and I 0 are equal to each other. (13) The left-hand half of the envelope is folded rightward along the line (C). On the obverse of the envelope the points corresponding to Q, 0, K, L, and P,are marked R, S, T,U, and V, respectively.
' Helmholz, L. J. Am. Chem. Soc. 1939, 61, 1544. Yamana, S. J. Chem. Educ. 1988, 65, 1071.
(14) The left-hand half of the envelope is unfolded. (151 The left- and right-hand parts and the upper part oftheenvelopes arerut off along the rigrag roune I)Pl.KOIQRJ.SI'(!VE, romomed of thr 13 lrnes DP. PL, LK, KO. 01. IQ. QK. K J , J S , ST. TU. UV. and VE. 1I6l ,--,o n t h e k r s e of the envelooe..the DOints corresoondine ta 8. R, I , J , 0, T,F, L, U,P, and marked Q*.R*,!*, J;; 0*, S*, K*, T*, P, L*, U*, P*, and V*, respectively. (17) Oblique lines are drawn to shade eight harpoons (IOKF, JFTS, FLPD, and FEVU on the front and I*O*K*F*, J*F*T.S*, F L * P D , and F*EV*U* on the hack). (18) Eight regular triangles (IFJ, TFU, FDE, and KLFon the front and I*F*J*. T*F*US. F*DE. and K*L*F* on the hack) are marked o , . a . , a , , ad, h ~b:,, b,. and b,, respertrvely). (19) Twu rectangles rQlJR on the front and Q*I*JSR*on the back) are marked d l and c ~ resperrwely , (20) T h r enwlope is folded both hnckward and forward along the lines I J tm., P J * ) , KU %i.e.,K*lJw),O \ ' tie., O*lr*), IK (i.e., I./.''>, J D 1i.e.. J a D J ,SP,i.e..S-PI,and TL (ie.. I"/.',. (21) The original back of the envelope is unfolded downward along the line-DE. (22) On the front of the envelooe. the eight corners I, J,T. U. E. D. L. -. and K..of the four tri&eles a,. a*. and a;. are foreed approach earh orher so tharthe idur lines IJ. ~ 1 ED, ' . and LK form n square, infolding the timr shaded harpoons inside. The sides are taped cogether to form a trtragonal pyramid having four slopes a,, ar, or, and a+ (23) On the original hack of the envelope, which has already been unfolded downward along the line DE, the eight corners D, E, U*. T*. J*..I*..K*..and L*. of the four trianeles b:i.., b?. . b,. .. and br. are'foreed to approach each other s o that the four lines DE; U * F , J*I*, and K*L* form a square, infolding the shaded ~
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harpoons inside. The sides are taped together t
