Editing Structural formula (section)

=== Unspecified stereochemistry ===
[[File:Skeletal Structure of Cyclic D-Fructose.svg|thumb|left|175px|[[Fructose]], with a bond at the [[hydroxyl]] (OH) group upper left of image with unknown or unspecified stereochemistry]]
Wavy single bonds represent unknown or unspecified stereochemistry or a mixture of isomers. For example, the adjacent diagram shows the [[fructose]] molecule with a wavy bond to the {{chem2|HOCH2\s}} group at the left. In this case the two possible ring structures are in chemical equilibrium with each other and also with the open-chain structure. The ring automatically opens and closes, sometimes closing with one stereochemistry and sometimes with the other.{{cn|date=January 2025}}

Skeletal formulas can depict [[cis-trans isomerism|''cis'' and ''trans'' isomers]] of alkenes. Wavy single bonds are the standard way to represent unknown or unspecified stereochemistry or a mixture of isomers (as with tetrahedral stereocenters). A crossed double-bond has been used sometimes, but is no longer considered an acceptable style for general use.<ref name="IUPAC-2006">{{cite journal |author=J. Brecher |year=2006 |title=Graphical representation of stereochemical configuration (IUPAC Recommendations 2006) |url=http://www.iupac.org/publications/pac/pdf/2006/pdf/7810x1897.pdf |journal=[[Pure and Applied Chemistry|Pure Appl. Chem.]] |volume=78 |issue=10 |pages=1897–1970 |doi=10.1351/pac200678101897 |s2cid=97528124}}</ref>

[[File:E-Z notation in alkenes.svg|thumb|400px|center|Alkene stereochemistry]]