Rearrangements Concerted with Fragmentation of Cyclopropylmethoxychlorocarbene and Cyclobutoxychlorocarbene in Hydrocarbon Solvents and Ar Matrices

Fragmentations of cyclopropylmethoxychlorocarbene (6) and cyclobutoxychlorocarbene (10) lead
to rearrangments that afford mixtures of cyclopropylmethyl chloride (7), cyclobutyl chloride (8), and 3-butenyl
chloride (9). Isotopic substitution studies show that these rearrangments are accompanied by partial
exchange of the methylene groups within 6 and 10. Surprisingly, these processes that are typical of
carbocations persist in hydrocarbon solvents such as pentane and cyclohexane-d12. Quantum chemical
calculations reveal that the cis-conformers of the incipient oxychlorocarbenes C4H7OC̈Cl decay to C4H7Cl
+ CO via transient hydrogen bonded C4H7δ+···Clδ- complexes which possess significant ion pair character,
even in the gas phase or in nonpolar solvents. In contrast to benzyloxychlorocarbene, no free radicals are
formed upon generation or photolysis of 6 or 10 in Ar matrixes, although acid chlorides (the recombination
products of these radical pairs) are observed. The IR spectra obtained in these experiments show the
presence of several conformers of the two C4H7OC̈Cl.