HNCS interstellar

A A2 — transition, 278, 282 interstellar, 120 molecular orbitals, 265ff principal axes, 103 structure determination, 132ff vibrations, 90ff H2CS (thioformaldehyde) interstellar, 120 HNCO (fukninic acid) interstellar, 120 HNCS (thiofulminic acid) interstellar, 120... 

A second successful prediction is that many so-called metastable species (i.e. isomers) are abundant even if they are quite reactive in the laboratory.66 Perhaps the simplest interstellar molecule in this class is HNC, but large numbers of others can be seen in Table 1. It is assumed that most metastable species are formed in dissociative recombination reactions along with their stable counterparts at approximately equal rates, and that both are destroyed by ion-molecule reactions so that the laboratory reactivity, which is normally determined by reactions with neutral species, is irrelevant. Both HCN and HNC, for example, are thought to derive from the dissociative recombination reaction involving a linear precursor ion ... 

Molecular astronomy of carbon molecules is very rich. Of about 120 known interstellar molecules more than three-quarters contain carbon atoms diatomic molecules include CO, CN, C2, CH, CH+, CN+, and CO+ polyatomic include CH2, CH4, C2H2j CH OH, CH3CH2OH, H2CO and HNC large complex unsaturated radicals and polycyclic aromatic hydrocarbons are also detected. These all play a role in the thermochemistry of interstellar clouds. The 2.6-millimeter line of CO diagnoses density and temperature in molecular clouds, as do other molecules. 

Nobels RH, Random L, HOC+ An observable interstellar species A comparison with the isomeric and isoelectronic HCO+, HCN and HNC, Chem Phys, 60, 1-10 (1981)... 

To date 150 species have been detected in the interstellar space.1 Among these species only a handful of molecules have been spatially resolved in disks CO (and the isotopomers 13CO and C180), CN, HCN, DCN, HNC, H2CO, C2H, CS, HCO+, H13CO+, DCO+, and N2H+ (Koemer Sargent 1995 Dutrey etal. 1997 ... 

In regard to Schaefer s assertion that the existence of HNC in interstellar space is given a fairly firm theoretical foundation, lide made the following qualification in a postconference comment. 

The following species have heen detected in interstellar space (a) CH, (h) OH, (c) C2, (d) HNC, (e) HCO. Draw Lewis structures for these species and indicate whether they are diamagnetic or paramagnetic. 

After a presentation of the specificities of the interstellar medium, the knowledge of which is necessary to understand its chemistry, we turn to 2 different chemical systems, considered as analogs in standard astrochemistry models HCN/HNC and HNSi/HSiN. 

Among the astrochemical problems is the puzzling variability of the HNC/HCN abundance ratio in interstellar clouds [74,77], Although the previous model concludes that HCN and HNC should be produced almost in the same quantity, the abundance ratio of these species is observed to vary ... 

Both HNC and HCN have been known for a long time in the interstellar medium. According to the previous calculations, no explanation has been found for the temperature dependence of the HNC/HCN ratio. None of the reactions proposed by the astrochemical models can explain this fact up to now. Therefore, other processes should be searched. Among them, C -f NH2 and N + CH2 are being currently investigated theoretically. 

Just as in the diatomics with 10 valence electrons (VE), the 10 VE system HCN is one of the most stable species, occupying all A-B bonding MOs, and it has therefore received considerable attention in a number of experimental studies. It is linear in its ground state according to Walsh s rules. " The isomer HNC was first observed by Milligan and Jacox about 20 years ago and later an emission line observed at 90 665 MHz in interstellar space s was... 

Theoretical elucidation of the vmusually high (HNC]/[HCN] abundance ratio in interstellar space Two-dimensional and two-state quantum wave packet dynamics study on the branching ratio of the dissociative recombination reaction HCNH-" + e HNC/HCN + H. The Astrophysical Journal, 636, 927. 

HCN is formed in interstellar clouds through one of two major pathways via a neutral-neutral reaction (CH2 + N HCN + H) and via dissociative recombination (HCNH + e HCN + H). The dissociative recombination pathway is dominant by 30% however, the HCNH must be in its linear form. Dissociative recombination with its structural isomer, H2NC produces hydrogen isocyanide (HNC), exclusively. 

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. 

HNC is intricately linked to the formation and destruction of numerous other molecules of importance in the interstellar medium - aside from the obvious partners HCN, HCNH, and CN, HNC is linked to the abundances of many other compounds, either directly of through few degrees of separation. As such, an understanding of the chemistry of HNC leads to an understanding of countless other species - HNC is an integral piece in the complex puzzle representing interstellar chemistry. 

HNC is found primarily in dense molecular clouds, though it is ubiquitous in the interstellar medium. HNC is formed primarily through the dissociative recombination of HNCH and H2NC, and it is destroyed primarily through ion-neutral reactions with Hs and C. Rate constants are taken from udfa.net, and data on fractional abundances is taken from here. Rate calculations were done at 3.16x10 years, which is considered early time, and at 20K, which is a typical temperature for dense molecular clouds. 

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