Cyclopropenylidene radical

The discovery of cyclopropenylidene radical (172) in laboratory and in space was reported277 in 1985. Its ring geometry is similar to that of 171 (Table 18). The cyclic "C3H radical... 

The discovery of cyclopropenylidene radical (172) in laboratory and in space was report-ed in 1985. Its ring geometry is similar to that of 171 (Table 18). The cyclic C3H radical (173) is another interstellar species, observed also in laboratory. It has Qv symmetry and a nearly equilateral triangular shape in the 2 state. The bond lengths are from MW spec-tra , r, (H)C—C 1.3750, C C 1.3745 and C—H 1.0747 A. 

Fig. 19. The unimolecular reaction channels for the propargyl radical together with the heats of reaction. Assuming that H2 loss is associated with a substantial reverse barrier, formation of cyclopropenylidene, c-C3H2, is the most likely channel. (From Deyerl et a/.143)...

In cyclopropenylidene m=n=0) the highest occupied polyene radical (S) has the correct symmetry for interaction with the px orbital (S). Mixing of these orbitals leads to two new orbitals of different energy px is destabilized, and a is stabilized by bending, which reinforces the splitting of the a and the delocalized p level. This is shown in the interaction diagram for cyclopropenylidene (7). 

Cyclopropenones, alkoxy, 177 Cyclopropenones, benzo, 180 Cyclopropenones, hydroxy, 170 Cyclopropenyl radicals, 187 Cyclopropenylidene, 187... 

The exciting discoveries of Interstellar hydrocarbon ring molecules have been very recent. Cyclopropenylidene, C-C3H2, appears to be widely distributed in the Interstellar medium millimetre-wave transitions of C-C3H2 have recently been identified in emission in several cold molecular dust clouds and in absorption in the direction of the galactic center (4). The detection of the related cyclic C3H radical molecule has been reported just recently (5). Toward mc-l the column density of C-C3H is comparable to that of linear C3H, I-C3H, and is about one order of magnitude lower than that of C-C3H2 (5). 

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