Do-It-Yourself 5-Color 3D Printing of Molecular Orbitals and Electron Density Surfaces

This report outlines an approach for preparing 5-color 3D printed plastic models of molecular orbitals and electron density surfaces using a hobby-grade 3D printer. Instructions are provided for preparing 3D orbital and electron density surface (EDS) models using solid or mesh representations in ground state and transition state structures. We show that the information content of 3D orbital and surface models can be enhanced with text annotation, bisection, strut and dashed bond placement, and composite orbital-EDS model constructions. Example prints illustrate orbital concepts in organic and inorganic chemistry, such as the ethyl cation (a-p hyperconjugation), methane (hybridization and C-H bonding), ethane (a-a* hyperconjugation in the staggered and eclipsed conformations), 2-hydroxytetrahydropyran (the anomeric effect/n-a* hyperconjugation), the water dimer (hydrogen bonding/n-a* overlap), ethylene, 1,3-butadiene, and benzene (x molecular orbitals), Re2Cl82-, and U2(COT)2 (metal-metal quadruple bonds). Transition state models illustrate orbital interactions in the SN2 reaction of cyanide with methyl, ethyl, and isopropyl chloride and in a hydroboration reaction of BH3 with propene. Composite EDS models of methyl and isopropyl chloride (for exploring their relative reactivities as SN2 electrophiles) and methylcyclohexane (visualizing 1,3-diaxial interactions) are described. Student perceptions of a multicolor 3D orbital print used in an introductory organic chemistry laboratory course are reported.