Three-Dimensional Representation -- Wedge Formula

The simplest way to recover genuine three-dimensional information from a flat page is the solid-and-dashed wedge convention. For a tetrahedral carbon bonded to four groups (labelled a, b, c, d for a generic example), bonds that lie roughly in the plane of the paper are drawn as ordinary straight lines; a bond projecting OUT of the page, towards the person looking at it, is drawn as a solid wedge (or a heavy line); and a bond projecting BEHIND the page, away from the observer, is drawn as a dashed wedge (or a dashed line). This lets a single flat drawing unambiguously convey which two of th …