The Cooper Structure-A
Simple Model to Illustrate the Tetrahedral Geometry of sp3 Bonding
A unique model for illustrating the tetrahedral geometry of spS bonding is obtained when the pattern in the figure is cut out and assembled as follows: (1)After removing the central circle in eaeh of the four parts that make up the pattern bend up along the two dotted lines in each part until the two separated points meet. (2) Bend down along the solid line between each pair of parts until two small adjacent triangles (one from each part) are back-to-back. (3) Fasten all pairs of back-to-back triangles taeach other either with glue or by taping adjacent edges together. The resulting structure is a tetrahedron with four recessed faces and a central hole and has been named the Cooper Structure. Each face is recessed in such a way as to produce a model that clearly shows the relative pasitioa of four bands extending from the center af a tetrahedron, one towards eaeh apex. This model was designed by William H. Freeman for inclusion in "Organic Chemist~y-How to Solve It (I. Molecular Geometry)" by Ruth A. Wdket, after Mr. Freeman observed models made by Roger Hayward, the illustrator of the organic workbook published by Freeman, Cooper and Co. in 1972. Ruth A. Walker Herbert H. Lehman College, CUNY Bronx, New Yark 10468
Volume 50, Number 10, October 1973
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