An Easily Constructed Monocapped Trigonal Prism Shukichi Y a m a n a Faculty of General Education, Kinki University. Kowakae, Higashi Osaka 577, Japan
A model of a monocapped trigonal prism, which is useful for teaching stereochemistry (for example of t h e heptafluoroniohate ion NhF+)' can h e m a d e easily b y using a sealed e m p t y envelope. T h e steps are illustrated i n the figure a n d given below. (1) The envelope is folded down the center lengthwise, and the middle point of the base AB is marked C. (2) The middle pointsof thelines AC and CB aremarkedD andE, respectively. (3) Three vertical lines, perpendicular to the hase AB at each of the three points D, C, and E, are drawn and they are marked (D), (C), and (E), respectively. (4) The right lower part of the envelope is folded up at A so that the hase AB falls on the left-hand side of the envelope. The point corresponding to the Cis marked F. (5) The right lower part of the envelope is unfolded. (6) A horizontal line, perpendicular to the left-hand side of the envelope at F, is drawn so that it crosses the lines (D) and (E) and the right-hand side of the envelope at G, H, and I , respectively.
' Brown. Georae M.; Walker. Lewis A. Acta Crystallogr. 1966, 20.
(7) The right lower part of the envelope is folded leftward at F so that the point Ifalls an the line (C). The corresponding point is marked J. (8) The right lower part of the envelope is unfolded. (9) The intersection of the lines F J a n d (D) is marked K. (10) . . A horizontal line oeroendicular to the line (Dl . . a t K..is drawn so that it crosses th; left (or right)-hand side of the envelope and the line (C) at L(or M and M, respectively. (11) The lower part of the envelope is folded up along the line FI. On the original front of the envelope, the points corresponding to the L and N a r e marked L' and N', respectively. (12) The lower part of the envelope is unfolded. (13) The upper part of the envelope is cut off along the line LN. (14) The lower parts of the envelope are cut off along the lines L'D and EN'. (15) On the reverse of the envelope, the points corresponding to M, G, and H are marked M*, G*, and H*, respectively. (16) The envelope is folded both backward and forward along the lines FI, (D), (E), ML' (i.e., M*L'), MN' (i.e., M'N'), LG (i.e., LG*), and NH (i.e., NH*). (17) Oblique lines are drawn to shade the eight triangles (LGM, MHN, GL'D, and HEN' on the front and LGaM*, M*H*N, G'L'D, and H'EN' on the back). (18) The back of the envelope is cut along the two lines DG* and ~
Volume 65
Number 12
December 1988
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(19, The lowrr partr uf the front irf the envelope are foldrd 30 [hat r h h~ e GI.' rur 11" falls on the line GD tor H E ) .
EH'. The new corners of the two shaded triangles are marked D* and E*,respectively.
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Journal of Chemical Education
(20) The lower parts of the envelope are unfolded. (21) The right- and left-hand sides of the envelope are pushed together so that the four lines GH, HH*, H'G*, and G*G form a square. (22) Points L' and D are pressed together and the shaded triangles (GL'D and G*L'Dn) are folded inside. Points E and N' are pressed together and the shaded triangles (HEN'andH*E*N') are folded inside. The sides are taped together to form the lower half of the model given in the title. (23) Four points M, N , M', and L are pushed together, and the four shaded triangles (LGM, MHN, M*H*N, and LG'M*) are folded inside. The sides are taped together to produce the model desired.
