Drawing Stereoisomeric Structural Formulas

This new version of the Molecular Editor allows the user to draw specific stereoisomers. Problems created earlier, do not recognize stereoisomers such as cis- & trans-2-butene, and the wedge bond tool in the menu is absent.
Both chiral and achiral stereoisomers are handled by the Editor. The isomers (E/Z) of appropriately substituted double bonds are automatically recognized. Isomerism due to chiral centers is specified by the wedge/hatched bond tool. Repeated clicking on a bond alternates its orientation. Two of the bonds to a chiral center must lie in the plane of the drawing and must connect heavy atoms (not hydrogen). The remaining two bonds will then be drawn as wedge and hatched lines. The (S)-2-bromo-2-chlorobutane example on the right shows a number of applications of this notation. In general, it is best to draw a carbon chain or ring in the reference plane and place substituents above or below that plane, as in the first drawing next to the Fischer formula. Do not try to draw Fischer projection formulas, the Editor will not recognize them. Do not draw hydrogen substituents at chiral centers, they are assigned an up or down orientation by default, as shown in the meso-2,3-butanediol example.

Using the Drawing Window, practice drawing the structures shown on the right below. When you have finished drawing a structure, check it by pressing the Check Molecule # button.

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Evaluation Window

Example 1. (S)-2-bromo-2-chlorobutane (see above)

Example 2. meso-2,3-butanediol (see above)

Example 3.

Example 4.

Example 5.

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