Effects of molecular representation on chemistry students' understanding of R and S configuration

This study explored the effect of molecular representation, three-dimensional dash-and-wedge or Fischer projection, when assigning R and S configuration to a molecule. In addition, common student difficulties noted while they assigned of absolute configuration for three-dimensional representations and Fischer projections were identified.;Think-aloud interviews were conducted with nine participants to further explore this relationship and also to determine where difficulties arise in assigning R and S configuration. These interviews along with questionnaire responses were analyzed and themes developed. Results suggest that mentally orienting the molecule when using a three-dimensional representation and correctly remembering rules when using Fischer projections are the most common difficulties encountered as students' assign R and S configuration.;Research results indicate that students use many different approaches to assign absolute configuration, many of which are devised by themselves. Evidence confirms that use of models, either mental or physical, is key to students building their understanding of the spatial aspects of molecular representations. Further research into the development of student visualization skills and spatial ability is recommended.;Spatial abilities were assessed using the Purdue Visualization of Rotations Test (ROT) and the Find-a-Shape Puzzle (FASP). Instruments were administered at the course's start to 133 first-semester organic chemistry students at two institutions; a large private university and a small two-year public college. A four-item questionnaire was developed to probe participants' understanding of assignment of absolute configuration. An ANOVA was conducted to investigate the relationship between spatial ability and choice of molecular representation. No significant relationship was found between spatial ability and choice of representation.