A Dynamic Carbon Model Capable of Showing Changes in Hybridization
he worth the undertaking for the benefit gained.
It is possible to construct a simple dynamic model of a carbon atom which demonstrates the Walden inversion, the SNI reaction, and when joined with one other unit like itself demonstrates the full spectrum of elimination reactions. The cost of this versatile model is so low that numbers of them have been made and distributed to students a t NMSU in a lab exercise with models which results in deep insight as t o the actual mechanics of these reactions. To construct the model one needs a practice golf balL2swizzle sticks, and Dow Corning silicone rubber bathtubcaulk. One inserts the main swizzle stick through appropriate holes in the plastic golf ball so as to form an axis. Through holes a t 120° toeaehother3 a t the equator ofthe ball one then inserts swizzle sticks each havingadaubof caulking on the end. (The transition state corresponds t o pseudoDsh symmetry.) These meet a t the axial stick, and when the caulk dries i t remains flexible. Plastic tubes such as found in the Organichem model set4 are inserted over the appropriately trimmed sticks t o give a c h i d center when the axial stick is displaced so as to allow a tetrahedral configuration. The nucleophile and nucleofuge are placed along the axial stick. Motion of the axial stick in either direction causes the A, B and C ligands to move in the opposite direction as the exposed axial stick. As the nucleophile becomes more attached, by sliding the plastic tube onto the axis swizzle stick, the ligands A, B, and C distort from Dsh symmetry and adopt more and more the tetrahedral configuration.
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Figure 2. E2 elimination via dynamic model. Figure 1. Dynamic model The El,ElCb, and El renrtwns are all equnlly well reprrtentrd hg the mudel.
