H2CS 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 major class of ion-molecule reactions that is relatively poorly studied consists of systems involving very unsaturated hydrocarbon neutrals, especially radicals. The unsaturated nature of the organic chemistry in interstellar clouds leads to sizeable abundances of very unsaturated hydrocarbons such as the polyacetylenes HC H, the carbenes H2C , the radicals C H, and the clusters Cn. Although some work has been done on the chemistry of such species, much of the relevant ion-molecule chemistry involving ions such as C+, CH3, and even C2H2 must be guessed at from generalizations based on a small number of studied systems. 

Studies of the isomers of this species were undertaken because of a particularly vexing problem relating to the chemistry in interstellar molecular clouds. This is that propynal, HC=C-CHO, has been observed but its isomer propadienone, H2C=C=C=0, has not, although searches have been made in the most molecule-rich clouds, the Taurus Molecular Cloud and Sagittarius B2.85 A possible route to these isomers is the reaction,86... 

In neutralization-reionization mass spectrometric experiments on CH2Si+ formed by electron-impact dissociative ionization of ClCH2SiH3, Srinivas, Stilzle and Schwarz found evidence for the formation of a viable neutral molecule whose fragmentation pattern and collisional activation mass spectrum were in accord with a H2C=Si structure422. These authors suggested that their experiments supported electron-capture by CH2Si+" as a mechanism for the formation of H2C=Si in interstellar space. Various models have predicted that H2C=Si is one of the most abundant forms of silicon in dense interstellar clouds423. 

Vibrational data have been reported for silylidene, H2C=Si and D2C=Si, Table 11. ° An ab initio calculation has been reported for the vibrational wavenumbers of the 2-silaketenylidene radical, CSiO, ° and for the ground and first excited states of the 2-silaketenyl radical. Similar calculations for isomers of the interstellar molecule SiC2N suggest that only the chain-like isomers are likely to be stable. ... 

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