Planar Structures

Planar molecules such as benzene, ethene, and methanal are best drawn in the plane of the paper with bond angles of about 120^o. When it is desired to draw them as viewed on edge (out of plane) care must be taken to provide proper perspective. The forward bonds can be drawn with slightly heavier lines; a tapered bond indicates direction, the wide end pointing toward the viewer and the narrow end away from the viewer (Figure 5-11). Barred lines are used here to indicate a rear or receding bond (many writers use dashed lines, but these may be confused with other uses of dashed lines, as for partial bonds).

However, you will find other representations of planar carbons with rather grossly distorted bond angles. For example, methanoic acid is planar with nearly 120^o bond angles, but often is drawn with H−C−O angles of 90^o and 180^o:

The distorted structures commonly are used to save space and, regretfully, we have to use them very frequently for this reason.