Chemical reactivity of quintet carbenes, m-phenylenebis (phenylmethylene)(1) and m- phenylenebis (methylene)(2) has been studied. Dicarbene 1 adds to 1, 1-diphenylethylene (84%) and strongly abstracts an H atom, Dicarbene 1 has a triplet-like character. Photolysis of 1, 3-bis (α-diazomethyl)-benzene (6) in cis-2-butene results in nearly stereospecific cyclopropanation (98% cis-cis adducts, 20–22), accompanied by 2% trans-cis adducts (24 ...