Addition and insertion reactions of methylene

The carbenes are also effective excitation reagents in addition reactions. Methylene, H2C , is the parent compound in this series. It is also the most reactive. Its ground state is a triplet86, the reactions of which are principally hydrogen abstractions and non-stereospecific additions to carbon-carbon double bonds. 

Similarly, the reactions of methylene with saturated compounds and hydrogen require postulation of excited products to explain the kinetics98-100. The production of excited methyl cyclopropane 

Although highly excited and energetically able to decompose, the molecules formed either by H-atom or by H2C addition survive many vibrations. The energy of reaction is distributed over the entire molecule prior to isomerization or bond rupture. This has been deduced from analysis of the proportions of the various products that are formed (when more than one path is available). The proportions change very little, if at all, with excitation energy. Thus, for complex excited molecules, their history, i.e. mode of formation, becomes irrelevant in the analysis of subsequent reactions. 

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