Diazomethane insertion into ketene

CARBENE. The name quite generally used for the methylene radical, CH,. It is formed during a number of reactions. Thus the flash photochemical decomposition of ketene (CH2=C=0) has been shown to proceed in two stages. The first yields carbon monoxide and CHj. the latter then reacting with more ketene to form ethylene and carbon monoxide. Carbcne reacts by insertion into a C- H bond to form a C-CH, bond. Thus carbene generated from ketene reacts with propane to form, i-butane and isobutane. Carbene generated by pyrolysis uf diazomethane reacts with diethyl ether to form ethylpropyl ether and ethylisopropyl ether. 

A century ago, Nef could not know, by any means, how unstable methylene actually is and how much theoretical and (indirect) experimental work was necessary to obtain reliable information on its structure (bond length, bond angle) and its energy of formation In fact, reactions involving methylene and other carbenes, as metastable intermediates, were studied successfully in the first half of this century, e.g., by Staudinger and Kupfer (1912), who obtained ketene (H2C = C=0) when they pyrolyzed diazomethane in the presence of CO, or by Meerwein et al. (1942), who discovered the insertion of the methylene group of diazomethane into O — H and C-H bonds of alcohols. 

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