S N and ~ SN2 Reactions: Paper Marionette for Demonstration A paper-made "marionette" for classroom demonstration of the mechanisms of S N 1and S N reactions ~ will be described in this paper. All the necessary materials are carton paper of suitable size,2 a bit of strong paste, several rubber bands and felt-tip pens. The assembly of the marionette is shown in Figure 1. After cutting out the pieces A-I from the carton paper, and bending some of them as shown in Figure 1, the bottom of A is pasted on the tap of B, and the legs of B are inserted through the holes of C and D, and then through the canal of E and another hole of F, as shown by the vertical arrows in Figure 1. The lower ends of the legs are then bent open, and G is pasted to their soles from below, so that B e m serve as a two-legged pin holding all the pieces A-G toeether.,~and. a t the same time. allowine free rotation of the pieces C, D, and Faraund B and Figure 2. Front view of the finished Figure 1. Assembly of the mariafree sliding of the whole unit composed ofA-D, marionette (I), which also shows nette. F, and G along the canal on E. The ends of the pieces H and I are then bent down like key bits how to Connect the parts with cut as shown in Figure 1, and inserted into the knife cuts on both sides of E. Finally, the rubber bands, how to fix their knotpieces C. D, and F are rotated t o their positions shown in Figure 2, and their ends ted ends ( I l l , and how to play the are connected with E with cut rubber bands as shown in the same figure. (Important: marionette I I i i l the lengths of these bands must be adjusted so that, when the central unit is slid from one end of the canal to the other, the three protruding ends of C, D, and F remain nearly equidistant from hoth ends of E.) After the assembly is over, the letters C, a, b, c, X , and Yare written on the six "atoms" as in Figure 2, and they and their "bonds" are suitably colored or hatched with felt-tip pens of brilliant colors. The plat of the marionette play for an S N 2reaction will be nearly self-evident t o the reader. When the central unit is held by one's left hand, and the piece E is pushed horizontally by the right hand as shown in Figure 2, the marionette will play the change which occurs when a nudeaphilic reagent Y attacks an optically active molecule CabcX. As Y a p proaehes the molecule, the group X is driven off with its bonding pair (i.e., the "rod" in the model), leaving Cabc which. passing through . a -planar transition state, combines with Y and forms a new active molecule CabeY with inverted cbnrormatian. An SN1reaction can also he played with this marionette. In this case, the play is started with the marionette without Y. and E is pushed until the C atom comes t o the middle of E, showing the dissociation of X from the original molecule. X is then removed, and Y is attached either on the right-hand or left-hand side of E, and made to attack the earbonium ion either by pushing or pulling E,with resultant formation of CabeY with or without inversion. Ifproper care is taken in the assembly andplaying, impressive shows can be played with this simple marionette.
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1 Inquiries on this paper should be addressed to: Mrs. Yachiyo Sone, Hongo 4-20, Bunkyo-ku, Tokyo 113, Japan. 21t will be convenient t o use a strip of very thick paper, 2 x 12 in. in size, as the piece E, and cut out other pieces from another paper which is not too thick, in sizes which may be estimated from the figures.
Oohanamizu University Otsuka, Tokyo 112, J a p a n
Yachiyo Sone' Kozo Sone
Volume 50, Number 9, September 1973 / 615
