A theoretical study of the (ClC3H2)(+) species has been carried out. Two di
fferent models, the complete MP4 at MP2 geometries and the QCISD(T) at B3LY
P geometries, have been employed. Our calculations predict that the global
minimum is a cyclic isomer with a three-membered carbon ring, ClC3H2+((1)A(
1)), whereas two different open-chain structures, ClCCCH2+((1)A(1)) and ClH
CCCH+((1)A'), lie similar to 19 and 15 kcal/mol, respectively, higher in en
ergy. The lowest-lying triplet state is an open-chain structure, ClCCCH2+((
3)A "), which lies >57 kcal/mol above the global minimum. These theoretical
results allow the development of thermodynamic arguments about the reactio
n pathways of the process Cl+ +- C3H2 For the reaction of Cl+ with vinylide
necarbene (1-C3H2), the production of ClCCCH+ is both thermodynamically and
kinetically favored, and even the formation of ClC3H+ is also more exother
mic than the charge transfer. In the reaction of Cl+ with cyclopropenyliden
e (c-C3H2), the production of both cyclic and open-chain chlorine-carbon co
mpounds seems to be severely hindered; hence, charge transfer should be the
dominant process. Consequently, only the reaction of Cl+ with 1-C3H2 seems
to be a possible source of chlorine-carbon compounds in space, and the pre
ferred product should be linear ClCCCH+, which could be a precursor to ClCC
C.