Organic chemistry lecture course and exercises based on true scale models

Felix Lederle,Eike G Hübner

doi:10.1515/cti-2019-0006

Abstract

Abstract 3D models of chemical structures are an important tool for chemistry lectures and exercises. Usually, simplified models based on standard bond length and angles are used. These models allow for a visualized discussion of (stereo)chemical aspects, but they do not represent the true spatial conditions. 3D-printing technologies facilitate the production of scale models. Several protocols describe the process from X-ray structures, calculated geometries or virtual molecules to printable files. In contrast, only a few examples describe the integration of scaled models in lecture courses. True bond angles and scaled bond lengths allow for a detailed discussion of the geometry and parameters derived therefrom, for example double bond character, aromaticity and many more. Here, we report a complete organic chemistry/stereochemistry lecture course and exercise based on a set of 37 scale models made from poly(lactic acid) as sustainable material. All models have been derived from X-ray structures and quantum chemical calculations. Consequently, the models reflect the true structure as close as possible. A fixed scaling factor of 1 : 1.8·108 has been applied to all models. Hands-on measuring of bond angles and bond length leads to an interactive course. The course has been evaluated with a very positive feedback.

Highlights

Visualization of 3D structures and spatial orientation has always been a major aspect of chemistry lectures (Oliver-Hoyo & Babilonia-Rosa, 2017)
X-ray structures taken from the Cambridge Structural Database have been used as source for most 3D models intended for a discussion of bond length and angles and other spatial phenomena
The lecture course and exercises have been evaluated by the Clausthal University of Technology Center for Quality Management in study and teaching before and after introduction of the scale models

Summary

Introduction

Visualization of 3D structures and spatial orientation has always been a major aspect of chemistry lectures (Oliver-Hoyo & Babilonia-Rosa, 2017). For the understanding of complex geometries in the 3D space, molecular modelling kits with standardized sets of atoms and bonds are indispensable. Modern technologies allow for significantly improved representations of complex molecular structures. The technology of 3D-printing has been applied to generate true 3D models as scaled counterparts to the original molecular structure. These models can be handled as objects from molecular modelling kits, but have one significant advantage: They represent exactly scaled bond lengths and bond angles instead of standardized atom distances.

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Discussion

Conclusion