The linear isomer of C3H2 was first
Cernicharo et al.
in 1991 in
Taurus Molecular Cloud 1
(TMC-1), the closest known region of low-mass star
the linear form of C3H2 is a
carbene species, where the terminal carbon has fewer bonds
than the optimal four that carbon generally possesses. It is also a
cumulene molecule by virtual of its pair
of aligned and adjacent double bonds. Cumulenes have a -C=C(=C)n- backbone.
The l-C3H2 is slightly less stable
energetically than the cyclic form. There are other isomers as well, including
quasi-linear HCCCH and other cylic arrangements. None of the other structures have been observed in the ISM.