Push, Pivot, and Pull Your Way to Converting Fischer Projections into Staggered Bond-Line Structures

Abstract

Interconverting different molecular representations can be problematic for many organic chemistry students. This is certainly the case when converting Fischer projections into bond-line structures. When performing the conversion from a Fischer projection into an all-staggered bond-line structure, students are sometimes taught to draw the fully eclipsed conformer first; for smaller molecules, the conversion to a fully eclipsed bond-line representation is relatively straightforward, while the conversion into the staggered conformation is not always as trivial. A systematic approach using the mnemonic "push−pivot−pull" described herein provides organic chemistry students with another option for producing a staggered bond-line structure from the corresponding Fischer projection while foregoing the fully eclipsed representation altogether.

Arrow-Rotation-Method “ARM”, a Simple and Fast Method for Interconverting Fischer Projections and Zigzag Structures

“…Moreno reported a multistep process to convert Fischer projections into zigzag forms and vice versa . Recently, Butler reported two different multistep procedures for interconverting Fischer projections and zigzag forms. , Despite the usefulness of the newly reported methods, the development of alternative methods that are more time-efficient and less dependent on 3D visualization is needed, especially for students who have problems with such visualizations. This communication presents the “Arrow-Rotation-Method” (ARM) for interconverting Fischer projections and zigzag structures in a few simple steps that require only 2D visualization.…”

“…Converting one molecular representation into another is among the main learning objectives of an introductory organic chemistry course. , Mastering the skill of converting one molecular representation into another requires understanding the 3D structure of each form, performing the necessary operations to complete the transformation, and then executing it. − Three-dimensional visualization of molecules is essential for chemistry-major students; however, for nonmajors or students with a certain level of aphantasia, this can be difficult and overwhelming. ,− Using model kits or computer software can help in 3D visualization; − however, such techniques are only reliable in classroom activities involving small molecules and are impractical for large molecules or during exams. , Despite the importance of this topic, interconverting the different molecular representations has received little attention in undergraduate organic chemistry textbooks, , and the development of simple, practical, and student-friendly techniques remains necessary. Several methods have been reported for the interconversion of the different molecular representations. ,− However, only a few have been reported about interconverting zigzag structures and Fischer projections. ,− The traditional approaches for completing such interconversions that involve drawing the fully eclipsed conformation, using the “absolute configuration assignment” method, or 3D visualization are usually time-consuming and impractical, especially for compounds with multiple chiral centers. − In this context, Mandal described a method for converting the 3D bond-line structure of a chiral center into a Fischer projection to facilitate absolute configuration assignment . Moreno reported a multistep process to convert Fischer projections into zigzag forms and vice versa .…”