- An old term, which is not recommended, for alkenes, especially those of low molecular weight.
- An old term for alkanediyl groups commonly but not necessarily having the free valencies on adjacent carbon atoms, e.g. propylene (systematically called propane-1,2-diyl).
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1314 (https://doi.org/10.1351/pac199567081307)