CarbenesR2C:
formed by mono or dialkyl substitution of
methylene,
H2C:, e.g.
CH3CH2CH:
propylidene.
Source:
PAC, 1995, 67, 1307
(Glossary of class names of organic compounds and reactivity intermediates based on
structure (IUPAC Recommendations 1995))
on page 1314