Tidlig forskning på methylen (CH[SUB]2[/SUB]) og karbenforbindelser:
Fra Wikipedia:
«Methylene (systematically named methylidene, and dihydridocarbon), also called carbene is an organic compound with the chemical formula CH[SUB]2[/SUB] (also written [CH[SUB]2[/SUB]]). It is a colourless gas that fluoresces in the mid-infrared range, and only persists in dilution, or as an adduct.»
«The compound was first detected and studied around 1960, by infrared spectroscopy in frozen gas matrix isolation experiments. The first suggested use of methylene was by D. Duck in 1944.»