Ultraviolet photochemistry of diacetylene with alkynes and alkenes: Spectroscopic characterization of the products
- Purdue Univ., West Lafayette, IN (United States). Dept. of Chemistry
The primary reaction products formed when metastable diacetylene (C{sub 4}H{sub 2}{sup *}) reacts with ground-state diacetylene (C{sub 4}H{sub 2}), ethylene (C{sub 2}H{sub 4}), and propene (CH{sub 3}{single_bond}CH{double_bond}CH{sub 2}) have been spectroscopically characterized using a laser pump-probe scheme. Reaction is initiated in a constrained expansion which limits reaction times to about 20 {micro}s. The molecular structures of the C{sub 6}H{sub 2} product formed in the C{sub 4}H{sub 2}{sup *} + C{sub 4}H{sub 2} reaction is identified from its R2PI spectrum and two-photon ionization threshold (9.49 {+-} 0.01 eV) as triacetylene (H{single_bond}C{triple_bond}C{single_bond}C{triple_bond}C{single_bond}C{triple_bond}C{single_bond}H). The analogous scans of the C{sub 8}H{sub 2} product show a clear two-photon ionization onset at 9.09 {+-} 0.02 eV, but little resolved vibronic structure above this threshold, consistent with its assignment as tetraacetylene. The R2PI spectra of the C{sub 6}H{sub 4} product formed in the reactions of C{sub 4}H{sub 2}{sup *} with C{sub 2}H{sub 4} and CH{sub 3}{single_bond}CH{double_bond}CH{sub 2} lead to an identification of this product as 1-hexene-3,5-diyne (CH{sub 2}{double_bond}CH{single_bond}C{triple_bond}C{single_bond}C{triple_bond}CH). The C{sub 7}H{sub 6} product formed in the reaction of C{sub 4}H{sub 2}{sup *} with CH{sub 3}{single_bond}CH{double_bond}CH{sub 2} possesses an R2PI spectrum close to that of 1-hexene-3,5-diyne, supporting its identification as a methylated derivative with the same ene-diyne structure. Two C{sub 7}H{sub 6} isomers meet this criterion, 5-heptene-1,3-diyne (CH{sub 3}{single_bond}CH{double_bond}CH{sub 2}{single_bond}C{triple_bond}C{single_bond}C{triple_bond}C{single_bond}H) and 2-methyl-1-hexene-3,5-diyne (H{sub 2}C{double_bond}C(CH{sub 3})-C{triple_bond}C{single_bond}C{triple_bond}C{single_bond}H), between which the authors cannot distinguish. Implications for the mechanisms for these C{sub 4}H{sub 2}{sup *} reactions are discussed.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG02-96ER14656
- OSTI ID:
- 335230
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Vol. 103, Issue 10; Other Information: PBD: 11 Mar 1999
- Country of Publication:
- United States
- Language:
- English
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