Tricarbon monosulfide (C3S) or tricarbon sulfur is a reactive molecular substance that has been detected in
outer space
Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, pred ...
. Tricarbon monosulfide is a
heterocumulene A heterocumulene is a molecule or ion containing a chain of at least three double bonds between consecutive atoms, in which one or more atoms in the doubly bonded chain is a heteroatom. Such species are analogous to a cumulene in which the chain of ...
or thiocumulene, consisting of a straight chain of three
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...
debye
The debye (symbol: D) (; ) is a CGS unit (a non- SI metric unit) of electric dipole momentTwo equal and opposite charges separated by some distance constitute an electric dipole. This dipole possesses an electric dipole moment whose value is g ...
. The bond lengths are 1.275 Å, for terminal C=C bond, 1.292 Å for internal bond, and 1.535 Å for the C=S bond. The similar bond lengths between the carbon atoms indicate they each have a
double bond
In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betwee ...
nature. The rotational constants for 12C12C12C32S are B0 = 2890.38000 MHz and D0 = 0.00022416.
There is a characteristic infrared absorption band at 2047.5 cm−1 due to stretching of a C=C bond.
Formation
Along with the related dicarbon monosulfide (CCS), tricarbon monosulfide was made by a glow discharge though
carbon disulfide
Carbon disulfide (also spelled as carbon disulphide) is a neurotoxic, colorless, volatile liquid with the formula and structure . The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical n ...
vapour in helium. Microwave emission lines from rotational transitions matched up with previously unknown molecular lines from the Taurus molecular cloud 1. Maximal concentrations occurred with a carbon disulfide pressure of 0.02
torr
The torr (symbol: Torr) is a unit of pressure based on an absolute scale, defined as exactly of a standard atmosphere (). Thus one torr is exactly (≈ ).
Historically, one torr was intended to be the same as one " millimeter of merc ...
.
In molecular clouds, the formation mechanism is speculated to be CCS + CH → CCCS + H.
On dust grains, in space the formation mechanism is theorised to be: CCC + H2S → C3•HSH → CCCS + H2 when irradiated with visible or UV light. THis reaction has been reproduced in a solid argon matrix.
Natural occurrence
Tricarbon monosulfide has been detected in
molecular cloud
A molecular cloud, sometimes called a stellar nursery (if star formation is occurring within), is a type of interstellar cloud, the density and size of which permit absorption nebulae, the formation of molecules (most commonly molecular hydroge ...
s in space, such as the Taurus molecular cloud and the Kleinmann–Low Nebula. The ratio of tricarbon monoxide to tricarbon monosulfide reflects the ratio of sulfur to oxygen in the cloud. The ratio of concentration of sulfur to oxygen analogues follows the same pattern. The clouds can be cold and dark, or warm. CCCS has also been found in the stellar envelope of carbon-rich AGB stars, including in IRC+10216.