Divalent groups formed by removing two hydrogen atoms from a hydrocarbon, the free valencies of which are not engaged in a double bond, e.g. 1,3-phenylene,
–CH2CH2CH2– propane-1,3-diyl,
–CH2–methylene.
Source:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1341 (https://doi.org/10.1351/pac199567081307)