The synthesis of 1, 1-difluoro-2-(dideuteriomethylene)-cyclopropane is reported along with the kinetics of its competing, reversible, first order rearrangements:(a) the degenerate rearrangement to 1, 1-difluoro-3, 3-dideuterio-2-methylene-cyclopropane, and (b) its rearrangement to 2, 2-dideuterio-1-(difluoromethylene)-cyclopropane. The observed experimental ratio of these two rate constants, 2.3, is consistent with Borden's theoretically ...