What Is a Wedge and Dash Projection in Chemistry?

A wedge and dash projection is a drawing, a means of representing a molecule in which three types of lines are used in order to represent the three-dimensional structure:

1. Solid lines to represent bonds that are in the plane of the paper
2. Dashed lines to represent bonds that extend away from the viewer
3. Wedge-shaped lines to represent bonds oriented facing the viewer

Although there is no hard-and-fast rule for drawing a wedge and dash structure, most people find it easiest to visualize the three-dimensional shape of a molecule if the pair of bonds in the same plane as the paper is drawn next to each other, and the bonds in front of and behind the plane are also drawn next to each other (as in the example shown).

Although the wedge-and-dash is the most common method of representing molecules in 3D, there are other diagrams you may encounter, including the sawhorse diagram and Newman projections.