Methylidenecarbene
（重定向自Vinylidene）
Methylidenecarbene (systematically named λ-ethene and dihydrido-1κH-dicarbon(C—C)) is an organic compound with the chemical formula C=CH
2 (also written [CCH
2] or C
2H
2). It is a metastable proton tautomer of acetylene, which only persists as an adduct. It is a colourless gas that phosphoresces in the far-infrared range. It is the simplest unsaturated carbene.