 | |
| Names | |
|---|---|
| IUPAC name 1,2-Propadien-1-yl-3-ylidene | |
| Other names 2-Propyn-1-ylidyne; 2-Propynylidyne | |
| Identifiers | |
3D model (JSmol) | |
PubChem CID | |
| |
| |
| Properties | |
| C3H | |
| Molar mass | 37.041 g·mol−1 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
Propynylidyne is a chemical compound that has been identified in interstellar space.
μD=3.551 Debye [1]
2Π electronic ground state
A rotational spectrum of the 2Π electronic ground state of l-C3H can be made using the PGopher software (a Program for Simulating Rotational Structure, C. M. Western, University of Bristol, http://pgopher.chm.bris.ac.uk) and molecular constants extracted from the literature. These constants include μ=3.551 Debye [1] and others provided by Yamamoto et al. 1990, [2] given in units of MHz: B=11189.052, D=0.0051365, ASO=432834.31, γ=-48.57, p=-7.0842, and q=-13.057. A selection rule of ΔJ=0,1 was applied, with S=0.5. The resulting simulation for the rotational spectrum of C3H at a temperature of 30 K agree well with observations. [2] The simulated spectrum is shown in the figure at right with the approximate atmospheric transmission overplotted in blue. All of the strongest simulated lines with J < 8.5 are observed by Yamamoto et al. [2]
μD=2.4 Debye [3] electronic ground state
The molecule C3H has been observed in cold, dense molecular clouds. The dominant formation and destruction mechanisms are presented below, for a typical cloud with temperature 10K. The relative contributions of each reaction have been calculated using rates and abundances from the UMIST database for astrochemistry. [3]
| Reactant 1 | Reactant 2 | Product 1 | Product 2 | Rate Constant | Contribution |
|---|---|---|---|---|---|
| C3H3+ | e− | C3H | H2 | 1.0E-7 cm3s−1 | 81.2% |
| C | C2H2+ | C3H | H+ | 2.18E-10 cm3s−1 | 18.8% |
| Reactant 1 | Reactant 2 | Product 1 | Product 2 | Rate Constant | Contribution |
|---|---|---|---|---|---|
| O | C3H | CO | C2H | 1.7E-11 cm3s−1 | 95.4% |
| N | C3H | C3N | H | 1.7E-11 cm3s−1 | 3.7% |
| H3+ | C3H | C3H2+ | H | 2.0E-9 cm3s−1 | 0.7% |
| C+ | C3H | C4+ | H | 1.0E-10 cm3s−1 | 0.2% |
| H+ | C3H | C3+ | H2 | 2.0E-9 cm3s−1 | <<1% |
The C3H molecule provides the dominant pathway to the production of C4H+, and thereby all other CnH (n>3) molecules via the reactions:
These reactions produce the majority of C4H+, which is necessary for the production of higher-order carbon-chain molecules. Compared to the competing reaction,
C3H3+ + C → C4H2+ + H,
also shown right, the destruction of C3H provides a much faster pathway for hydrocarbon growth.
Other molecules in the C3H family, C2H and C3H2, do not significantly contribute to the production of carbon-chain molecules, rather forming endpoints in this process. The production of C2H and C3H2 essentially inhibits larger carbon-chain molecule formation, since neither they nor the products of their destruction are recycled into the hydrocarbon chemistry.
The first confirmation of the existence of the interstellar molecule C3H was announced by W.M Irvine et al. at the January 1985 meeting of the American Astronomical Society. [4] The group detected C3H in both the spectrum of the evolved carbon star IRC+10216 and in the molecular cloud TMC-1. These results were formally published in July of the same year by Thaddeus et al. [5] A 1987 paper by W.M. Irvine provides a comparison of detections for 39 molecules observed in cold (Tk ≅10K), dark clouds, with particular emphasis paid to tri-carbon species, including C3H. [6]
Later reports of astronomical detections of the C3H radical are given in chronological order below.
In 1987, Yamamoto et al. [7] report measurements of the rotational spectra of the cyclic C3H radical (c-C3H) in the laboratory and in interstellar space towards TMC-1. This publication marks the first terrestrial measurement of C3H. Yamamoto et al. precisely determine molecular constants and identify 49 lines in the c-C3H rotational spectrum. Both fine and hyperfine components are detected toward TMC-1, and the column density for the line of sight toward TMC-1 is estimated to be 6x1012cm−2, which is comparable to the linear C3H radical (l-C3H).
M.L Marconi and A. Korth et al. [8] reported a likely detection of C3H within the ionopause of Comet Halley in 1989. Using the heavy ion analyzer (PICCA) on board the Giotto spacecraft they determined that C3H was responsible for producing a peak at 37amu detected within ~4500 km of the comet nucleus. Marconi et al. argue that a gas phase progenitor molecule for C3H is unlikely to exist within the ionopause and suggest that desorption from circumnuclear CHON dust grains may have instead produced the observed C3H.
In 1990, Yamamoto et al. [2] detected C3H toward IRC + 10216 using the Nobeyama Radio Observatory's 45-m radio telescope. They determine an upper limit for the column density of the ν4 state 3x1012cm−2. From additional laboratory measurements they determine an extremely low vibrationally excited state for the C3H radical: ν4(2Σμ)=610197(1230) MHz, caused by the Renner-Teller effect in the ν4 (CCH bending) state.
J.G. Mangum and A. Wootten [9] report new detections of c-C3H towards 13 of 19 observed Galactic molecular clouds. They measure relative abundance of C3H to C3H2: N(c-C3H)/N(C3H2) = 9.04±2.87 x 10−2. This ratio does not change systematically for warmer sources, which they suggest provides evidence that the two ring molecules have a common precursor in C3H3+.
L.A. Nyman et al. [10] present a molecular line survey of the carbon star IRAS 15194-5115 using the 15m Swedish-ESO Submillimetre Telescope to probe the 3 and 1.3 mm bands. Comparing the molecular abundances with those of IRC + 10216, they find C3H to have similar abundances in both sources.
In 1993, M. Guelin et al. [11] map the emission from the 95 GHz and 98 GHz lines of the C3H radicals in IRC+10216. This reveals a shell-like distribution of the C3H emission and time-dependent chemistry. The close correspondence between the emission peaks of C3H and the species <noautolink>MgNC</noautolink> and C4H suggests a fast common formation mechanism, suggested to be desorption from dust grains.
Turner et al. [12] survey 10 hydrocarbon species, including l-C3H and c-C3H in three translucent clouds and TMC-1 and L183. Abundances are measured or estimated for each. The mean cyclic-to-linear abundance ratio for C3H is found to be 2.7, although a large variation in this ratio is observed from source to source.
In 2004, N. Kaifu et al. [13] completed the first spectral line survey toward TMC-1 in the frequency range 8.8-50.0 GHz with the 45-m radio telescope at Nobeyama Radio Observatory. They detected 414 lines of 38 molecular species including c-C3H and compiled spectral charts and improved molecular constants for several carbon-chain molecules.
Martin et al. [14] made the first spectral line survey towards an extragalactic source, targeting the starburst galaxy NGC253 across the frequency range 129.1-175.2 GHz. Approximately 100 spectral features were identified as transitions from 25 different molecular species, including a tentative first extra-galactic detection of C3H.
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 hydrogen, H2), and the formation of H II regions. This is in contrast to other areas of the interstellar medium that contain predominantly ionized gas.
In astronomy, the interstellar medium (ISM) is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space. The energy that occupies the same volume, in the form of electromagnetic radiation, is the interstellar radiation field. Although the density of atoms in the ISM is usually far below that in the best laboratory vacuums, the mean free path between collisions is short compared to typical interstellar lengths, so on these scales the ISM behaves as a gas (more precisely, as a plasma: it is everywhere at least slightly ionized), responding to pressure forces, and not as a collection of non-interacting particles.
Astrochemistry is the study of the abundance and reactions of molecules in the universe, and their interaction with radiation. The discipline is an overlap of astronomy and chemistry. The word "astrochemistry" may be applied to both the Solar System and the interstellar medium. The study of the abundance of elements and isotope ratios in Solar System objects, such as meteorites, is also called cosmochemistry, while the study of interstellar atoms and molecules and their interaction with radiation is sometimes called molecular astrophysics. The formation, atomic and chemical composition, evolution and fate of molecular gas clouds is of special interest, because it is from these clouds that solar systems form.
The hydroxyl radical is the diatomic molecule •
OH. The hydroxyl radical is very stable as a dilute gas, but it decays very rapidly in the condensed phase. It is pervasive in some situations. Most notably the hydroxyl radicals are produced from the decomposition of hydroperoxides (ROOH) or, in atmospheric chemistry, by the reaction of excited atomic oxygen with water. It is also important in the field of radiation chemistry, since it leads to the formation of hydrogen peroxide and oxygen, which can enhance corrosion and SCC in coolant systems subjected to radioactive environments. The unpaired electron of the hydroxyl radical is officially represented by a middle dot, •, beside the O.
The trihydrogen cation or protonated molecular hydrogen is a cation with formula H+
3, consisting of three hydrogen nuclei (protons) sharing two electrons.
CW Leonis or IRC +10216 is a variable carbon star that is embedded in a thick dust envelope. It was first discovered in 1969 by a group of astronomers led by Eric Becklin, based upon infrared observations made with the 62 inches (1.6 m) Caltech Infrared Telescope at Mount Wilson Observatory. Its energy is emitted mostly at infrared wavelengths. At a wavelength of 5 μm, it was found to have the highest flux of any object outside the Solar System.
The ethynyl radical (systematically named λ3-ethyne and hydridodicarbon(C—C)) is an organic compound with the chemical formula C≡CH (also written [CCH] or C
2H). It is a simple molecule that does not occur naturally on Earth but is abundant in the interstellar medium. It was first observed by electron spin resonance isolated in a solid argon matrix at liquid helium temperatures in 1963 by Cochran and coworkers at the Johns Hopkins Applied Physics Laboratory. It was first observed in the gas phase by Tucker and coworkers in November 1973 toward the Orion Nebula, using the NRAO 11-meter radio telescope. It has since been detected in a large variety of interstellar environments, including dense molecular clouds, bok globules, star forming regions, the shells around carbon-rich evolved stars, and even in other galaxies.
Hydrogen isocyanide is a chemical with the molecular formula HNC. It is a minor tautomer of hydrogen cyanide (HCN). Its importance in the field of astrochemistry is linked to its ubiquity in the interstellar medium.
Octatetraynyl radical is an organic free radical with eight carbon atoms linked in a linear chain with alternating single bonds and triple bonds.
HCNH+, also known as protonated hydrogen cyanide, is a molecular ion of astrophysical interest. It also exists in the condensed state when formed by superacids.
Cyclopropenylidene, or c-C3H2, is a partially aromatic molecule belonging to a highly reactive class of organic molecules known as carbenes. On Earth, cyclopropenylidene is only seen in the laboratory due to its reactivity. However, cyclopropenylidene is found in significant concentrations in the interstellar medium (ISM) and on Saturn's moon Titan. Its C2v symmetric isomer, propadienylidene (CCCH2) is also found in the ISM, but with abundances about an order of magnitude lower. A third C2 symmetric isomer, propargylene (HCCCH), has not yet been detected in the ISM, most likely due to its low dipole moment.
The cyano radical (or cyanido radical) is a radical with molecular formula CN, sometimes written •CN. The cyano radical was one of the first detected molecules in the interstellar medium, in 1938. Its detection and analysis was influential in astrochemistry. The discovery was confirmed with a coudé spectrograph, which was made famous and credible due to this detection. ·CN has been observed in both diffuse clouds and dense clouds. Usually, CN is detected in regions with hydrogen cyanide, hydrogen isocyanide, and HCNH+, since it is involved in the creation and destruction of these species (see also Cyanogen).
In organic chemistry, cyanopolyynes are a family of organic compounds with the chemical formula HCnN (n = 3,5,7,…) and the structural formula H−[C≡C−]nC≡N (n = 1,2,3,…). Structurally, they are polyynes with a cyano group (−C≡N) covalently bonded to one of the terminal acetylene units (H−C≡C).
Imidogen is an inorganic compound with the chemical formula NH. Like other simple radicals, it is highly reactive and consequently short-lived except as a dilute gas. Its behavior depends on its spin multiplicity.
Stellar molecules are molecules that exist or form in stars. Such formations can take place when the temperature is low enough for molecules to form – typically around 6000 K or cooler. Otherwise the stellar matter is restricted to atoms in the forms of gas or – at very high temperatures – plasma.
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 doubly bonded atoms contains only carbon, except that at least one carbon is replaced by a heteroatom. Some authors relax the definition to include species with chains of only two double bonds between consecutive atoms, also known as heteroallenes.
Tricarbon monosulfide (C3S) or tricarbon sulfur is a reactive molecular substance that has been detected in outer space. Tricarbon monosulfide is a heterocumulene or thiocumulene, consisting of a straight chain of three carbon atoms and a terminal sulfur atom.
Phosphorus monoxide is an unstable radical inorganic compound with molecular formula PO.
HD 73882 is a visual binary system with the components separated by 0.6″ and a combined spectral class of O8. One of stars is an eclipsing binary system. The period of variability is listed as both 2.9199 days and 20.6 days, possibly due to the secondary being a spectroscopic binary star.
