A CROSSED MOLECULAR BEAM, LOW-TEMPERATURE KINETICS, AND THEORETICAL INVESTIGATION OF THE REACTION OF THE CYANO RADICAL (CN) WITH 1,3-BUTADIENE (C{sub 4}H{sub 6}). A ROUTE TO COMPLEX NITROGEN-BEARING MOLECULES IN LOW-TEMPERATURE EXTRATERRESTRIAL ENVIRONMENTS
- Institut de Physique de Rennes, Equipe Astrochimie Experimentale, UMR UR1-CNRS 6251, Universite de Rennes 1, Campus de Beaulieu 35042 Rennes Cedex (France)
- Department of Chemistry, National Dong Hwa University, Hualien, Taiwan (China)
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL (United States)
We present a joint crossed molecular beam and kinetics investigation combined with electronic structure and statistical calculations on the reaction of the ground-state cyano radical, CN(X {sup 2}{Sigma}{sup +}), with the 1,3-butadiene molecule, H{sub 2}CCHCHCH{sub 2}(X {sup 1} A{sub g}), and its partially deuterated counterparts, H{sub 2}CCDCDCH{sub 2}(X {sup 1} A{sub g}) and D{sub 2}CCHCHCD{sub 2}(X {sup 1} A{sub g}). The crossed beam studies indicate that the reaction proceeds via a long-lived C{sub 5}H{sub 6}N complex, yielding C{sub 5}H{sub 5}N isomer(s) plus atomic hydrogen under single collision conditions as the nascent product(s). Experiments with the partially deuterated 1,3-butadienes indicate that the atomic hydrogen loss originates from one of the terminal carbon atoms of 1,3-butadiene. A combination of the experimental data with electronic structure calculations suggests that the thermodynamically less favorable 1-cyano-1,3-butadiene isomer represents the dominant reaction product; possible minor contributions of less than a few percent from the aromatic pyridine molecule might be feasible. Low-temperature kinetics studies demonstrate that the overall reaction is very fast from room temperature down to 23 K with rate coefficients close to the gas kinetic limit. This finding, combined with theoretical calculations, indicates that the reaction proceeds on an entrance barrier-less potential energy surface (PES). This combined experimental and theoretical approach represents an important step toward a systematic understanding of the formation of complex, nitrogen-bearing molecules-here on the C{sub 5}H{sub 6}N PES-in low-temperature extraterrestrial environments. These results are compared to the reaction dynamics of D1-ethynyl radicals (C{sub 2}D; X {sup 2}{Sigma}{sup +}) with 1,3-butadiene accessing the isoelectronic C{sub 6}H{sub 7} surface as tackled earlier in our laboratories.
- OSTI ID:
- 21612647
- Journal Information:
- Astrophysical Journal, Vol. 742, Issue 1; Other Information: DOI: 10.1088/0004-637X/742/1/26; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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