Methylchlorocarbene. Solution electronic spectroscopy of alkyl- and alkylhalocarbenes is sparse because these species generally have weak absorptions and undergo rapid rearrangements. Nevertheless, we describe the sigma-p absorption of MeCCl at 545 nm obtained by laser flash photolysis (LFP) of methylchlorodiazirine in pentane at ambient temperature. Evidence is presented for complexation of MeCCl in anisole, which affects both its UV spectrum and the rate of its reaction with alkenes.

Dichlorocarbene. A new synthesis of dichlorodiazirine is described. LFP studies in solution at ambient temperature afford evidence for the reactions of dichlorocarbene with oxygen and pyridine. The sigma-p absorption of CCl₂ has thus far proven too weak to observe in solution.

Diazirinone. Diazirinone, the diaza analogue of cyclopropenone, is generated by ipso attack of fluoride ion on p-nitrophenoxychlorodiazirine. Diazirinone has a lifetime of about 5 minutes near ambient temperature, and its exothermic decomposition to N₂ and CO can be followed by IR spectroscopy.

Carbanions from carbenes. Reactions of phenylhalocarbenes (PhCX) with halide ions produce phenyldihalomethide carbanions (PhCXY^-) which add to electron deficient alkenes. Cyclization of the adduct anions with expulsion of halide ion then generates cyclopropanes. The kinetics of these processes are readily visualized by LFP. Examples are provided for the formation and reactions of PhCBr₂^- and PhCFBr^-.

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