Are Neutral-Neutral Reactions Effective for the Carbon-Chain Growth of Cyanopolyynes and Polyacetylenes in Interstellar Space?
- Department of Chemistry, Rikkyo University, 3-34-1 Nishi-ikebukuro, Toshima-ku, Tokyo 171 (Japan)
- Center for Computational Quantum Chemistry, University of Georgia, Athens, GA 30602-2556 (United States)
Ab initio molecular quantum-mechanical methods have been applied to explore the possibility of neutral-neutral reactions leading to the formation of cyanopolyynes and polyacetylenes in interstellar cloud. Potential energy surfaces for the reactions between the CN radical and polyacetylenes indicate that all reactions, C{sub 2{ital n}}H{sub 2} + CN ({ital n} = 1{endash}4), which form HC{sub 2n+1}N molecules, are exothermic and have no energy barriers. We have also examined the possibility of the various product channels from the reactions C{sub 2{ital n}}H{sub 2} + CN based on the thermochemical relationships. The theoretical results show that none of the product channels is exothermic except the case which produces HC{sub 2{ital n}+1}N, with the carbon chain being longer than the reactant polyacetylene. Similar results are obtained for the regioselectivity of the reactions, C{sub 2{ital n}}H{sub 2} + C{sub 2}H ({ital n} = 1{endash}4), to produce hydrocarbons. The only possible products from the latter reactions are shown to be HC{sub 2n+2}H + H under the conditions of interstellar space. These results clearly demonstrate the importance of the neutral-neutral reactions on the carbon-chain growth of cyanopolyynes and polyacetylenes. {copyright} {ital {copyright} 1998.} {ital The American Astronomical Society}
- OSTI ID:
- 303875
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 505; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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