Drawing Three Dimensional (3-D) Structures on Paper (continued)

Incorporating three dimensional information into line structures.

All of the lines (bonds) that we have used so far in drawing structures have been "normal" lines. These normal lines are used to represent bonds that lies in the plane of the drawing surface (i.e the computer screen, the paper, the chalkboard, etc.) In order to represent bonds projecting out of this plane, we use "dashed" and "wedged" bonds.

Dashed bonds are used to represent bonds that project backward (behind the drawing plane). While wedged bonds are used to represent bonds that project outward (in front of the drawing plane).

The three common types of bonds used in drawing chemical structures:

Thus, we can take a simple molecule such as methane and represent its tetrahedryl geometry using wedged and dashed bonds as follows:, compare this to the molecular model:

We can also use this convention to represent stereoisomers.. Take a look at the two stereoisomers of 2-bromobutane, which we looked at before. Rotate the 3D models so that they match the line structures. Note that it is possible to draw a number of different line structures representing different views of the same molecule (only two are shown below for each stereoisomer).

(S)-2-bromobutane

(R)-2-bromobutane



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