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Introduction


Definitions


Three-Dimensional Representations


Assigning Priorities


Determining Stereochemical Relationships


Question Sets


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Determining Stereochemical Relationships for Cyclic Structures




There are four different methods that can be used to determine the stereochemical relationship between cyclic molecules drawn using different three-dimensional representations. One of these methods utilizes the assignments of R and S in a molecule. The other three types are based on making physical comparisions to determine whether or not a pair of molecules can be related by superimposibility and a mirror image. Choose whether you feel most comfortable with assigning stereocenters with their R or S orientations, or whether you prefer a particular three-dimensional representation for comparing molecules. Select the option with which you feel most confident for making complex structural comparisons. Each section will have its own Testing Your Knowledge section and answer key, designed to match the option that you have chosen.

Recall that cyclic molecules can exist in various sizes, with the smallest ring containing three atoms. However, since six-membered rings (cyclohexane rings) are the most common in organic chemistry, the following sections will each focus on six-membered rings. The methods presented can be applied toward cyclic molecules of any size.

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