1. An old term, which is not recommended, for @A00224@s, especially those of low @M04000@.
  2. 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 [Terms] [Paper]