A Model To Show the S N Inversion ~ When wr werernnsidevingthcSr,2 mechanism in in? Orgmlc clssi, two of my students prcsrnrcd me with whar I brlwve to be a novel model for plrtunng the mversion of configuration. The model is made of paper or lightweight cardboard and is an equilateral triangle with another equilateral triangle an each edge. The three outer triangles can fold up or down tc make a tetrahedron. The inner triangle has a slit in the center through which a narrow strip of paper or cardboard passes. Starting with the tetrahedral shape, the strip "attacks" the face that has the slit in it. As the stripenters, the tetrahedron starts to come undone a t the opposite apex, step 1, see figure. The three outer triangles next pass though the flat, transition stage, step 2, and f i nally flap aver to envelop the strip, step 3, and the inversion is complete.
Richard D. Sands Devin C. Dressrnan Shawn R. Wyan Alfred University Alfred, NY 14802
428
Journal of Chemical Education
