Cyclopropenylidene (c-C3H2) was first
Thaddeus et at.
here) in 1985
in various sources, including
Orion A and in diffuse molecular
clouds. In spite of its unusual nature, this species is
widely observed and more thoroughly confirmed than many other astromolecules.
Two isotopic variants have also been observed, including monodeuterated c-C3HD
by Bell et al.
and the mass 13 isotope of C by
Gomez-Gonzalez et al.
and Madden et al.
It has also been observed in extragalactic sources, including
NGC 5128 by
Seaquist & Bell and
NGC 253 and
Tomoko et al.
UPDATE (July 2018): Cyclopropenylidene was detected in the protoplanetary disk
HD 163296 by
Qi et al. in 2013.
The ground electronic state of cyclopropenylidene is a singlet. There is also a
triplet state which is somewhat higher in energy. Both forms are examples of
species that possess a carbon with only two bonds instead of the usual four.
(CH2) is the prototypical carbene. They tend to be very reactive. Hence,
cyclopropenylidene is thought to be a precursor for various other astromolecules.